The Mosque-Cathedral of Cordoba: Graphic Analysis of Interior Perspectives by Girault De Prangey Around 1839

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International Journal of Geo-Information

Article The Mosque-Cathedral of Cordoba: Graphic Analysis of Interior Perspectives by Girault de Prangey around 1839

Antonio Gámiz-Gordo 1,* , Juan Cantizani-Oliva 2 and Juan Francisco Reinoso-Gordo 3

1 Architectural Graphic Expression Department, University of Seville, 41012 Seville, Spain 2 Electrical and Automatic Engineering Department, University of Cordoba, 14071 Cordoba, Spain; [email protected] 3 Architectural and Engineering Graphic Expression Department, University of Granada, 18071 Granada, Spain; [email protected] * Correspondence: [email protected]

Abstract: The work of Philibert Girault de Prangey, who was a draughtsman, pioneering photographer and an Islamic architecture scholar, has been the subject of recent exhibitions in his hometown (Langres, 2019), at the Metropolitan Museum (New York, 2019) and at the Musée d’Orsay (Paris, 2020). After visiting Andalusia between 1832 and 1833, Prangey completed the publication “Monuments arabes et moresques de Cordoue, Seville et Grenada” in 1839, based on his own drawings and measurements. For the ﬁrst time, this research analyses his interior perspectives of the Mosque-Cathedral of Cordoba (Spain). The novel methodology is based on its comparison with a digital model derived from the point cloud captured by a 3D laser scanner. After locating the different viewpoints, the geometric precision and the elaboration process are analysed, taking into account historic images by various authors, other details published by Prangey and the architectural transformations of the Citation: Gámiz-Gordo, A.; Cantizani-Oliva, J.; Reinoso-Gordo, building. In this way, the veracity and documentary interest of some beautiful perspectives of a J.F. The Mosque-Cathedral of monument inscribed on the World Heritage List by UNESCO is valued. Cordoba: Graphic Analysis of Interior Perspectives by Girault de Prangey Keywords: Mosque-Cathedral; Cordoba; Girault de Prangey; view; perspective; 3D laser scanner around 1839. ISPRS Int. J. Geo-Inf. 2021, 10, 181. https://doi.org/ 10.3390/ijgi10030181 1. Introduction Academic Editors: Wolfgang Kainz 1.1. Brief Historical Overview of the Mosque-Cathedral of Cordoba and Andreas Georgopoulos Over the centuries, the Mosque-Cathedral of Cordoba has been transformed and adapted to the needs of each period, without losing the essential features of its archi- Received: 12 February 2021 tectural identity [1]. In its long history, three major stages can be considered, which are Accepted: 14 March 2021 Published: 19 March 2021 outlined below. The ﬁrst Umayyad mosque was built in the middle of the 8th century by Abd al-

Publisher’s Note: MDPI stays neutral Rahman I, with arches and parallel naves that facilitated the southern expansion by Abd with regard to jurisdictional claims in al-Rahman II and later by Al-Hakam II. The last eastern extension was completed by published maps and institutional affil- Almanzor in the 10th century, filling a space with surprising interior perspectives between iations. columns and double horseshoe arches [2–4]. The skylight of the first mihrab, today the Villaviciosa chapel, and three other ones next to the Al-Hakam II mihrab were especially important for its natural lighting [5]. The second stage began with the town conquest by King Ferdinand III in 1236. While other mosques in the Iberian Peninsula were demolished and replaced by churches or Copyright: © 2021 by the authors. cathedrals, the Mosque of Cordoba was used as a Christian temple and survived with Licensee MDPI, Basel, Switzerland. This article is an open access article important transformations. Around 1313, the Capilla Real (Royal Chapel) was built inside distributed under the terms and the cathedral for the burial of Ferdinand IV of Castile, together with the Villaviciosa conditions of the Creative Commons Chapel [6]. Between 1523 and 1607, a large volume was erected in the building centre that Attribution (CC BY) license (https:// heavily altered it [7] and, progressively, the inner perimeter was occupied by chapels. In creativecommons.org/licenses/by/ the first quarter of the 18th century, many naves were covered with plaster vaults, new 4.0/).

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skylights were opened and the interiors were covered with lime to achieve greater clarity skylightsskylights were were opened opened and and the the interiors interiors were were covered covered with with lime lime to to achieve achieve greater greater clarity clarity and visual unity. and visual unity. and Avisual third unity. stage began around 1815, after restoring the entrance arch to the mihrab. In the A third stage began around 1815, after restoring the entrance arch to the mihrab. In secondA halfthird of stage the 19th began century, around the 1815, altarpiece after restoring in the Villaviciosa the entrance Chapel arch was to the removed mihrab. and In theitsthe originalsecond second half skylight half of of the the was 19th 19th revealed. century, century, Between the the altarp altarp 1864ieceiece and in in 1884,the the Villaviciosa Villaviciosa the lime coating Chapel Chapel was was was removed. removed removed In and1887,and its its the original original architect skylight skylight Ricardo was was Vel revealed.á revealed.zquez Bosco Between Between took over1864 1864 theand and building 1884, 1884, the the conservation, lime lime coating coating and was was since re- re- moved.then,moved. architectural In In 1887, 1887, the the pieces architect architect from Ricardo Ricardo different Velázquez Velázquez periods have Bosco Bosco been took took recovered over over the the [building8 building]. This monument conserva- conserva- tion,wastion, inscribedand and since since on then, then, the Worldarchitectural architectural Heritage piece piece Lists s infrom from 1984 different different and the periods propertyperiods have have was beenextended been recovered recovered to include [8] [8]. . ThispartThis monument of monument the Historic was was Centre inscribed inscribed in 1994 on on the [9the] (FiguresWorld World Heritage 1Heritage–3). List List in in 1984 1984 and and the the property property was was extendedextended to to include include part part of of the the Historic Historic Centre Centre in in 1994 1994 [9] [9] (Figures (Figures 1 1––3).3).

FigureFigureFigure 1. 1.1. The TheThe geographical geographical geographical location location location of of ofCordoba Cordoba Cordoba in in southern insouthern southern Europe Europe Europe and and andthe the Mosque the Mosque Mosque-Cathedral-Cathedral-Cathedral placementplacementplacement downtown downtowndowntown near nearnear the thethe Guadalquivir GuadalquivirGuadalquivir river river river and and Roman Roman bridge. bridge.

(a(a) ) (b(b) )

FigureFigureFigure 2. 2.2. Inner InnerInner view: view:view: ( (a(aa)) )Mihrab MihrabMihrab front frontfront and andand ( (b(bb)) )Mihrab MihrabMihrab side. side.side. Source: Source:Source: Own OwnOwn photographs. photographs.photographs.

(a(a) ) (b(b) ) FigureFigure 3. 3. Inner Inner view: view: ( a(a) )columns columns forest forest and and ( b(b) )Royal Royal Chapel. Chapel. Source: Source: Own Own photographs. photographs.

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skylights were opened and the interiors were covered with lime to achieve greater clarity and visual unity. A third stage began around 1815, after restoring the entrance arch to the mihrab. In the second half of the 19th century, the altarpiece in the Villaviciosa Chapel was removed and its original skylight was revealed. Between 1864 and 1884, the lime coating was removed. In 1887, the architect Ricardo Velázquez Bosco took over the building conservation, and since then, architectural pieces from different periods have been recovered [8]. This monument was inscribed on the World Heritage List in 1984 and the property was extended to include part of the Historic Centre in 1994 [9] (Figures 1–3).

Figure 1. The geographical location of Cordoba in southern Europe and the Mosque-Cathedral placement downtown near the Guadalquivir river and Roman bridge.

ISPRS Int. J. Geo-Inf. 2021, 10, 181 (a) (b) 3 of 24 Figure 2. Inner view: (a) Mihrab front and (b) Mihrab side. Source: Own photographs.

(a) (b)

FigureFigure 3. 3. InnerInner view: view: ( (aa)) columns columns forest forest and and ( (bb)) Royal Royal Chapel. Chapel. Source: Source: Own Own photographs. photographs.

1.2. Interior Views of the Mosque-Cathedral in the First Half of the 19th Century The Mosque-Cathedral of Cordoba has been illustrated in many images before the spread of photography around 1850. This graphic legacy is very important in heritage research and is complemented by other historical or archaeological documentary sources, both Muslim [10] and Christian [11], and with the analysis of the architectural reality itself. The first scaled plans of the monument were published by the Real Academia de Bellas Artes de San Fernando in Madrid in “Las Antigüedades Árabes de España” (1787– 1804) [12]. The first interior perspective appeared in Henry Swinburne’s book, “Travels through Spain, in the Years 1775 and 1776” (1779) [13]. The first collection of views was published in Alexandre Laborde’s book, “Voyage pittoresque et historique de l’Espagne” (1812, t. II) [14]. In the first third of the 19th century, the views of James C. Murphy were remarkable in “The Arabian Antiquities of Spain” (1813) [15], as were the ones by Isidore Taylor in “Voyage pittoresque en Espagne, et Portugal, et sur la cote d’Afrique” (1826–1832–1860) [16]. Particularly noteworthy views from the 1830s include those by David Roberts in “Picturesque sketches in Spain taken during the years 1832–1833” (1837) [17] and “The tourist in Spain. Andalusia” (1838, t. II) [18], by John Frederick Lewis in “Sketches of Spain & Spanish Character made during his Tour in that Country in the Years 1833–1834” (1837) [19], as well as the work of Girault de Prangey (the focus of this study), “Monuments Arabes et Moresques de Cordoue, Séville et Grenade, dessinés et mesurés en 1832 et 1833 . . . ” (1839) [20]. Later, other views of Francisco Javier Parcerisa were published in “Recuerdos y bellezas de España” (1855, t. 8) [21] and the plates of the Real Academia de Bellas Artes de San Fernando in Madrid entitled “Los Monumentos Arquitectónicos de España” (1852– 1881) [22]. Studies on these images have been scarce, though many have been re-produced repeatedly. A book by Nieto-Cumplido and Luca-de-Tena (1992) [23] compiled the main plans and drawings of the Mosque-Cathedral, but did not include urban or interior views. Another book by Cosano-Moyano (1999) [24] included all kinds of images from Cordoba. In three articles by Gámiz-Gordo and García-Ortega (2012, 2015 and 2018), the views of Alexandre Laborde in 1812 [25], David Roberts in 1833 [26] and others [27] have been analysed. The surveys on the monument preserved in the Real Academia de Bellas Artes de San Fernando have been part of an exhibition and catalogue curated by Almagro-Gorbea (2015) [28]. The first photographs and photographers of the Mosque-Cathedral, between 1844 and 1875, have been presented in a book by Gónzález (2018) [29]. Another book with current plans by Ruíz-Cabrero (2009) [30] and Herrero-Romero’s thesis on restoration in the 20th century (2015) should also be highlighted [31]. Furthermore, an article by Gámiz-Gordo (2019) [32] reviews graphic sources up to 1850. ISPRS Int. J. Geo-Inf. 2021, 10, 181 4 of 24

1.3. Girault de Prangey: Draughtsman, Traveller, Islamic Architecture Scholar and Photographer Joseph Philibert Girault de Prangey (1804–1892) was a draughtsman, pioneering photographer and scholar of Islamic architecture (Figure4a). The museum in his hometown, Langres (France), devoted a small book to him in 1998 [33] and, in 2020, the museum held an exhibition with a catalogue that provides abundant information and illustrates the artist’s solid education [34]. Prangey studied at the École des Beaux-Arts in Paris. He inherited a great fortune that allowed him to travel and indulge his interest in Islamic ISPRS Int. J. Geo-Inf. 2021, 10, x architecture. He took a trip to Italy in 1831 and others to Tunisia, Algeria, Spain and4 of Sicily 22 between 1832 and 1833. According to the date of one of his original drawings, on 4 October 1832, he embarked on his journey to Spain. Girault de Prangey appears in the visitor’s signature book kept theat Alhambra the Alhambra on 12 on November 12 November and and4 December 4 December 1832 1832 [35]. [ 35According]. According to the to theabovemen- abovemen- tionedtioned catalogue, catalogue, several several original original drawings drawings from from Granada areare signedsigned in in June June and and July July 1833, 1833,and and others others from from Tarragona Tarragona and an Barcelonad Barcelona in October in October 1833. 1833. Thus, Thus, he spent he spent several several months monthsin Andalusia, in Andalusia, but no but information no information is known is known about about his visits his visits to Seville to Seville and and Cordoba, Cordoba, except exceptfor hisfor publishedhis published views. views. AfterAfter this this stay, stay, Girault Girault de dePrangey Prangey published published “Monuments “Monuments Arabes Arabes et Moresques et Moresques de de Cordoue,Cordoue, Séville Séville et Grenade, et Grenade, dessinés dessin éets etmesurés mesuré ens en 1832 1832 et et1833... 1833 ...MosquéeMosqu deée Cordoue, de Cordoue, GiraldaGiralda et Alcazar et Alcazar de deSéville: Séville: vués vu générales,és générales, intérieurs, intérieurs, détails, détails, coupes coupes et plans et plans de deces ces monumentsmonuments”” [20] [20 printed] printed at the at the prestigious prestigious Lemercier Lemercier et Cie. et Cie. from from Paris Paris and and edi editedted by by VeithVeith et Hauser. et Hauser. According According to ads to ads at the at the time, time, the the pictures pictures of ofGranada Granada appeared appeared in 1836 in 1836 andand 1837, 1837, and and those those of Seville of Seville and and Cordoba Cordoba in 1839 in 1839 (Figure (Figure 4b).4b). OnOn the the cover, cover, the the Cordoba Cordoba views views are are said said to have to have been been drawn drawn in 1833 in 1833 by byGirault Girault de de Prangey,Prangey, althou althoughgh a general a general view view is is signed signed by by Leon Leon Auguste Auguste Asselineau asas aa draughtsman.draughtsman.Engravers Engravers whose whose names names appear appear on eachon each plate plate collaborated collaborated on theon the ﬁgures. figures. Such Such engravers en- graversinclude include Leon Leon Auguste Auguste Asselineau, Asselineau, Louis Louis Philippe Philippe Alphonse Alphonse Bichebois, Bichebois, Charles Charles Villemin, Villemin,William William Wyld, JeanWyld, Charles Jean Charles Danjoy, Danjoy, Paul Dumouza Paul Dumouza and Adolphe and Adolphe Jean Baptiste Jean Baptiste Bayot. Bayot.

(a) (b)

FigureFigure 4. (a 4.) Girault(a) Girault de Prangey de Prangey’s’s self self-portrait-portrait (1840). (1840). Source: Source: gallica.bnf.fr, gallica.bnf.fr, Bibliothéque Bibliothéque Nationale Nationale de France;de France; (b) Plate (b) Plate ads from ads from Granada Granada (1836 (1836 and 1837), and 1837), Cordoba Cordoba and Seville and Seville (1839). (1839). Source: Source: Private Pri- collection.vate collection.

In 1841,In 1841, Girault Girault de dePrangey Prangey published published the the book book entitled entitled “Essai “Essai sur sur l’architecture l’architecture des des ArabesArabes et des et des Mores, Mores, en enEspagne, Espagne, en enSicile Sicile et en et enBarbarie Barbarie”” [36] [36 that] that includes includes plates plates of the of the MosqueMosque of Cordoba, of Cordoba, which which will will be bementioned mentioned later. later. Furthermore, Furthermore, in 1842, in 1842, he hepublished published anotheranother book book entitled entitled “Choix “Choix d’ornements d’ornements moresques moresques de del’Alhambra l’Alhambra”” [37] [37 including] including some some viewsviews from from the the Andalusian Andalusian monument. monument. Between 1839 and 1849, the French historian Jules Gailhabaud published various editions of the work entitled “Monuments anciens et modernes...” including plates about the architecture history of different peoples ranging through all their periods [38]. Many authors collaborated on that publication, and some plates from the Mosque of Cordoba, that will be commented on later, were included. The invention of the daguerrotype in 1839 was a great interest to Prangey, who was using it to take images of monuments in Paris by 1841 [39]. He then decided to study other Mediterranean landmarks and, in 1842, began a three-year journey. He produced more than 800 daguerreotypes in Greece, Egypt, Syria, Lebanon, Turkey, and Jerusalem. In 1846, he published “Monuments arabes d’Égypte, de Syrie et d’Asie-Mineure dessinés et mesurés de 1842 à 1845” [40].

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Between 1839 and 1849, the French historian Jules Gailhabaud published various editions of the work entitled “Monuments anciens et modernes ... ” including plates about the architecture history of different peoples ranging through all their periods [38]. Many authors collaborated on that publication, and some plates from the Mosque of Cordoba, that will be commented on later, were included. The invention of the daguerrotype in 1839 was a great interest to Prangey, who was using it to take images of monuments in Paris by 1841 [39]. He then decided to study other Mediterranean landmarks and, in 1842, began a three-year journey. He produced more than 800 daguerreotypes in Greece, Egypt, Syria, Lebanon, Turkey, and Jerusalem. In 1846, he published “Monuments arabes d’Égypte, de Syrie et d’Asie-Mineure dessinés et mesurés de 1842 à 1845” [40]. These publications can be considered as complementary and offer a remarkable graphic synthesis on the characteristics and periods of Islamic art in the Mediterranean. Although Prangey’s theories have been nuanced by historiography, they contributed an incredibly unique value to his graphic work compared to other works of that time. His entire work and his interest in graphically documenting architecture has raised great interest since Christie’s London Auction auctioned the artist’s daguerreotypes in 2003 and 2004 [41–43]. The exhibition Monumental Journey: The Daguerreotypes of Girault de Prangey, held in 2019 at the Metropolitan Museum in New York, included 120 daguerreotypes taken during his Mediterranean journey, as well as paintings, watercolours and lithographs [44]. Between 2020 and 2021, the Musée d’Orsay in Paris devoted another exhibition to his activity as a photographer [45].

1.4. General Objectives Prangey made his own drawings and measurements in the Mosque-Cathedral, when photography did not yet exist, as the basis for his later published images. It is not known if in Cordoba he was able to use advanced instruments, such as the camera lucida, which he apparently had previously used [46,47]. In any case, the veracity of the data reflected in any drawing should not be taken for granted, as they are always more or less accurate personal views, with a graded simplification of reality. Assessing the precision or certainty from each drawing requires analysing the real model that contrasts the faithful description of the photograph. The interests or abilities of the draughtsman and even the possible manipulations of the original drawings for their stamping should also be considered. Studies on the images of Girault de Prangey in Andalusia are scarce. Some comments about his views of Granada in a book by Galera-Andreu on the romantic image of the Alhambra in the 19th century should be highlighted [48], as well as those in a book by Orihuela-Uzal and Tito-Rojo on the Casas del Chapiz [49]; in an article by Orihuela-Uzal about a hammam [50]; and in another recent one by Sánchez-Gómez and Piñar-Samos [51]. Prangey’s views of Cordoba have not been studied until now. There is also no research on the documentary reliability of the Mosque-Cathedral drawings prior to the appearance of photographs around 1850. It is only worth mentioning a study by Almagro-Gorbea on the precision of plans preserved in the Real Academia de Bellas Artes de San Fernando in Madrid [52], wich does not include anything on perspectives. The aim of this research is to analyse Girault de Prangey’s interior perspectives of the Mosque-Cathedral of Cordoba andto assess their veracity, geometric reliability and documentary interest, considering at that time Prangey had not yet begun to use daguerreotype as a technique for the documentary record of architectural heritage. To do this, a digital model with the geometry of the monument has been created using 3D laser scanner data, and then compared to Prangey’s perspectives, taking into account the transformations that the monument has undergone and the drawings by other authors. The digitisation of architectural heritage has undergone a great development in recent decades thanks to data collection technologies that allow accurate and efficient modelling [53]. There is an abundant literature on the use of the 3D laser scanner and the ISPRS Int. J. Geo-Inf. 2021, 10, 181 6 of 24

subsequent processing to obtain some meshes. Many articles refer to survey methods of historical buildings, civil structures, archaeological objects, etc. Others refer to processes for ISPRS Int. J. Geo-Inf. 2021, 10, x 6 of 22 generating heritage information models (as-built models) based on 3D digitisation [54–56]. Comparisons between historical drawings and 3D digitisation is a field where research can unveil important findings and they have got remarkable results [57]. In any case, it seems importantIt should tonot obtain be forgotten suitable accuracy,that the graphic considering documentation the model sizein architectural and whether heritage it is a completealways depends building on [58 the,59 ],interests certain or parts objectives [60,61], proposed structural in elements each case [62 [66]], decorative. Due to the de- large tailssize [63 ]of or the even Mosque isolated-Cathedral, sculptures it has [64]. been The necessary proceedings to sketch of the latestits details Graphical according Heritage to scale Internationaland accuracy Congress, in order held to streamlin in 2020, havee work. also A been careful reviewed simplification [65]. of reality has been car- riedIt should out to build not be a forgottensimple geometric that the graphicmodel and documentation obtain linear inperspectives architectural from heritage the point alwayscloud. depends The novelty on the of interests this research or objectives is to use proposed said digital in each model case to [66 assess]. Due the to perspectives the large sizeof of athe great Mosque-Cathedral, draughtsman of the it has 19th been century, necessary taking to sketchinto account its details the accordinghistory and to transfor- scale andmations accuracy of inthe order monument. to streamline work. A careful simplification of reality has been carried out to build a simple geometric model and obtain linear perspectives from the point cloud.2. Materials The novelty and of Methods this research is to use said digital model to assess the perspectives of a great draughtsman of the 19th century, taking into account the history and transformations 2.1. Prangey’s Images of the Mosque-Cathedral of Cordoba of the monument. The Langres exhibition catalogue [34] contains original drawings by Prangey that 2. Materialsgive an idea and of Methods his solid education as a draughtsman. However, his original views of Cor- 2.1.doba Prangey’s are not Images known, of the and, Mosque-Cathedral for this reason, ofthis Cordoba work focuses on the published plates, which wereThe reworked Langres exhibition by different catalogue engravers [34] for contains their stamping. original drawings by Prangey that give an idea ofIn his“Monuments solid education arabes as et a moresques draughtsman. de Cordoue... However,” his (1839) original [20],views a view of of Cordoba the mihrab arelithographed not known, and, by Asselineau for this reason, (Figure this work5a) appears focuses on on the the cover. published The plates plates,’ edges which are were com- reworkedposed of by details different and engravers ornaments for of their the stamping.building. In “MonumentsThe details mentioned arabes et above moresques were used de Cordoue in another... plat” (1839)e including [20], aa viewschematic of the plan mihrabof the lithographed building in byIslamic Asselineau times (Figure 5 5b).a) appears It marks on the the perspective cover. The plates’viewpoints edges that are ap- composedpear in ofother details plates, and all ornaments of which ofwere the produced building. in the Al-Hakam II extension, one of the most architecturally interesting parts of the monument.

(a) (b)

FigureFigure 5. Girault 5. Girault de Prangey: de Prangey: (a) Publication (a) Publication cover cover including including mihrab mihrab view view (Asselineau, (Asselineau, lit.) (b lit.)) Building (b) Building plant hypothesisplant hypothesis in the Islamicin the Islamic period. period. Source: Source: Monuments Monuments arabes arabes et moresques et moresques de Cordoue, de Cordoue, Seville Seville et Grenada, et Grenada, 1839. 1839.

The first plate (plate 1; Figure 6a) includes a general view of the Mosque-Cathedral and the Roman bridge in their urban context. It was drawn from the other bank of the Guadalquivir river by Asselineau, a collaborator of Prangey. Another exterior view (plate 4; Figure 6b) shows the access doorways to the Mosque.

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The details mentioned above were used in another plate including a schematic plan of the building in Islamic times (Figure5b). It marks the perspective viewpoints that appear in other plates, all of which were produced in the Al-Hakam II extension, one of the most architecturally interesting parts of the monument. The ﬁrst plate (plate 1; Figure6a) includes a general view of the Mosque-Cathedral and the Roman bridge in their urban context. It was drawn from the other bank of the ISPRS Int. J. Geo-Inf. 2021, 10, x 7 of 22 Guadalquivir river by Asselineau, a collaborator of Prangey. Another exterior view (plate 4; Figure6b) shows the access doorways to the Mosque.

(a) (b)

FigureFigure 6. Mosque-Cathedral 6. Mosque-Cathedral of Cordoba of Cordoba views: views: (a) The (a) GuadalquivirThe Guadalquivir river, river, the Roman the Roman bridge bridge and the and town the (Bichebois,town (Bichebois, lit.; Bayot,lit.; ﬁg.)Bayot, (b )fig.) Lateral (b) Lateral entrance entrance facade (Wyld,facade (Wyld, lit.). Source: lit.). Source: Monuments Monuments arabes arabes et moresques et moresques de Cordoue, de Cordoue 1839., 1839.

Prangey’sPrangey two’s two most most signiﬁcant significant interior interior perspectives perspectives focused focused on on the the surroundings surroundings of of thethe Mosque Mosque mihrab. mihrab. One One of them, of them, more more general general (plate (plate 5; Figure 5; Figure7a), comprises 7a), comprises the forest the forest of columnsof columns and the and double the double horseshoe horseshoe arches. arches. The other The other one (plate one (plate 7; Figure 7; Figure7b) is closest7b) is closest to theto mihrab the mihrab and frames and frames its intertwined its intertwined arches. arches. A perspective of the Royal Chapel was erroneously entitled Capilla de Villaviciosa (plate 2; Figure8a), which is located right next to it, where Abd al-Rahman II’s mihrab was. The archeries with double arches can be seen at the bottom of the drawing. Another plate including a mihrab sectional elevation is framed by decorative details (plate 8; Figure8b). In addition, Prangey composed two plates with capitals, muqarnas and ornaments from the Royal Chapel and the mihrab, represented by elevations or perspectives (plate 3; Figure9a, plate 6; Figure9b).

(a) (b) Figure 7. Girault de Prangey: (a) Front view from the forest of columns and mihrab (Villemin, lit.); (b) Mihrab side view (Wyld, lit.). Source: Monuments arabes et moresques de Cordoue, 1839.

A perspective of the Royal Chapel was erroneously entitled Capilla de Villaviciosa (plate 2; Figure 8a), which is located right next to it, where Abd al-Rahman II’s mihrab was. The archeries with double arches can be seen at the bottom of the drawing. Another plate including a mihrab sectional elevation is framed by decorative details (plate 8; Fig- ure 8b). In addition, Prangey composed two plates with capitals, muqarnas and ornaments from the Royal Chapel and the mihrab, represented by elevations or perspectives (plate 3; Figure 9a, plate 6; Figure 9b).

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(a) (b) Figure 6. Mosque-Cathedral of Cordoba views: (a) The Guadalquivir river, the Roman bridge and the town (Bichebois, lit.; Bayot, fig.) (b) Lateral entrance facade (Wyld, lit.). Source: Monuments arabes et moresques de Cordoue, 1839.

Prangey’s two most significant interior perspectives focused on the surroundings of ISPRS Int. J. Geo-Inf. 2021, 10, 181 8 of 24 the Mosque mihrab. One of them, more general (plate 5; Figure 7a), comprises the forest of columns and the double horseshoe arches. The other one (plate 7; Figure 7b) is closest to the mihrab and frames its intertwined arches.

(a) (b) ISPRS FigureInt. J. Geo 7.- Inf.Girault 2021, de10, Prangey:x (a) Front view from the forest of columns and mihrab (Villemin, lit.); (b) Mihrab side view8 of 22 Figure 7. Girault de Prangey: (a) Front view from the forest of columns and mihrab (Villemin, lit.); (b) Mihrab side view (Wyld,(Wyld, lit.). lit.). Source: Source: Monuments Monuments arabes arabes et et moresques moresques de de Cordoue, Cordoue 1839., 1839.

(a) (b)

FigureFigure 8. Girault8. Girault de de Prangey: Prangey: (a )(a Royal) Royal Chapel Chapel side side view view (Villemin, (Villemin, lit.); lit.); (b )(b Section-elevation) Section-elevation and and details details from from mihrab mihrab (Dumouxa,(Dumouxa, lit.). lit.). Source: Source: Monuments Monuments arabes arabes et et moresques moresques de de Cordoue, Cordoue 1839., 1839.

(a) (b) Figure 9. Girault de Prangey. (a) Details (Asselineau, lit.); (b) Details (Danjoy, lit.). Source: Monuments arabes et moresques de Cordoue, 1839.

Prangey published four plates on the Mosque-Cathedral of Cordoba in his work “Es- sai sur l’architecture des Arabes et des Mores, en Espagne, en Sicile et en Barbarie” (1841) [36]. One includes an elevation and details from the Villaviciosa Chapel (plate 3; Figure 10a). Another plate is a perspective section from the space next to the mihrab (plate 6; Figure 10b), which was drawn by Nicolás Chapuy, and it included in the same plate a similar image from a mosque in Toledo. It also includes a plate with coloured details (plate 4; Figure 11a) and another with Arabic inscriptions (plate 5; Figure 11b).

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(a) (b) ISPRS Int. J. Geo-Inf. 2021, 10, 181 9 of 24 Figure 8. Girault de Prangey: (a) Royal Chapel side view (Villemin, lit.); (b) Section-elevation and details from mihrab (Dumouxa, lit.). Source: Monuments arabes et moresques de Cordoue, 1839.

(a) (b)

Figure 9. GiraultFigure de 9. Prangey.Girault ( dea) Details Prangey. (Asselineau, (a) Details lit.); (Asselineau, (b) Details lit.); (Danjoy, (b) Details lit.). Source: (Danjoy, Monuments lit.). Source: arabes Monu- et moresques de Cordoue,ments 1839. arabes et moresques de Cordoue, 1839.

Prangey publishedPrangey four published plates on thefour Mosque-Cathedral plates on the Mosque of Cordoba-Cathedral in his of work Cordoba “Essai in his work “Es- sur l’architecturesai dessur Arabesl’architecture et des Mores,des Arabes en Espagne, et des Mores, en Sicile en etEspagne, en Barbarie” en Sicile (1841) et en [36 Barbarie]. ” (1841) One includes an[36]. elevation One includes and details an elevation from the and Villaviciosa details from Chapel the Villaviciosa (plate 3; Figure Chapel 10a). (plate 3; Figure Another plate is10a). a perspective Another plate section is froma perspective the space nextsection to thefrom mihrab the space (plate next 6; Figure to the 10 b),mihrab (plate 6; which was drawnFigure by 10b), Nicol whichás Chapuy, was drawn and it includedby Nicolás in Chapuy, the same and plate it aincluded similar imagein the same plate a ISPRS Int. J. Geo-Inf. 2021, 10, x 9 of 22 from a mosquesimilar in Toledo. image It alsofrom includes a mosque a platein Toledo. with colouredIt also includes details a (plate plate 4;with Figure coloure 11a)d details (plate and another with4; Figure Arabic 11a) inscriptions and another (plate with 5; FigureArabic 11inscriptionsb). (plate 5; Figure 11b).

(a) (b)

Figure 10. GiraultFigure 10.de Prangey:Girault de (a Prangey:) Villaviciosa (a) Villaviciosa Chapel facade Chapel (Bouillon, facade lit.); (Bouillon, (b) Section lit.);- (perspectiveb) Section-perspective from the surrounding mihrab (Chapuy,from the dib.; surrounding Asselineau, mihrab lit.). Source: (Chapuy, Essai dib.; sur l Asselineau,’architecture lit.). des Source:Arabes et Essai des surMores, l’architecture en Espagne des... 1841. Arabes et des Mores, en Espagne . . . 1841.

(a) (b) Figure 11. Girault de Prangey: (a) Details and mosaics (Dumouza, lit.); (b) Arabic inscriptions (Asselineau, lit.). Source: Essai sur l’architecture des Arabes et des Mores, en Espagne... 1841.

Furthermore, in Jules Gailhabaud’s work, “Monuments anciens et modernes...” (c. 1845) [38], there are five plates of the Mosque-Cathedral: three views copied from other authors; one with a general plan and section including details, drawn by J. Jourdan and based on Prangey (Figure 12a); and another with details drawn by Prangey and Niel (Fig- ure 12b).

(a) (b) Figure 12. Girault de Prangey: (a) General plan and section and details from the Mosque (Jourdan, dib.; Bury, eng.); (b) Mosque details (Prangey, dib.; Niel, dib.; Bury, eng.). Source: Monuments anciens et modernes... c. 1845.

ISPRS Int. J. Geo-Inf. 2021, 10, x 9 of 22

(a) (b) ISPRS Int. J. Geo-Inf. 2021, 10, 181 10 of 24 Figure 10. Girault de Prangey:(a ()a ) Villaviciosa Chapel facade (Bouillon, lit.); (b) Section(b) -perspective from the surrounding Figuremihrab 10. Girault(Chapuy, de dib.; Prangey: Asselineau, (a) Villaviciosa lit.). Source: Chapel Essai facade sur l’ (Bouillon,architecture lit.); des (b Arabes) Section et- perspectivedes Mores, enfrom Espagne the surrounding... 1841. mihrab (Chapuy, dib.; Asselineau, lit.). Source: Essai sur l’architecture des Arabes et des Mores, en Espagne... 1841.

(a) (b) (a) (b) Figure 11. Girault deFigure Prangey: 11. Girault(a) Details de and Prangey: mosaics (a) (Dumouza, Details and lit.); mosaics (b) Arabic (Dumouza, inscriptions lit.); ( b(Asselineau,) Arabic inscriptions lit.). Source: FigureEssai 11. sur Girault l’architecture de Prangey:(Asselineau, des Arabes (a) Details lit.). et Source:des and Mores, mosaics Essai en sur Espagne (Dumouza, l’architecture... 1841. lit.); des (b) Arabes Arabic et inscriptions des Mores, (Asselineau, en Espagne .lit.). . . 1841. Source: Essai sur l’architecture des Arabes et des Mores, en Espagne... 1841. Furthermore,Furthermore, in Jules in Gailhabaud’s Jules Gailhabaud work,’s “Monumentswork, “Monuments anciens anciens et modernes et modernes...... ” ” (c. (c. 1845)1845)Furthermore, [38 ],[38], there there are inare ﬁve Jules five plates Gailhabaudplates of of the the Mosque-Cathedral:’s Mosquework, “-MonumentsCathedral: three three anciens views views et copied modernes...copied from from” other(c. other1845) authors;authors; [38], one thereone with with are a fivea general general plates plan plan of andthe and Mosque section section including-Cathedral: including details, threedetails, views drawn drawn copied by by J. JourdanJ. from Jourdan other and and basedauthors;based on oneon Prangey Prangey with (Figurea general (Figure 12 plana);12a); and andand another sectionanother with including with details details details, drawn drawn bydrawn by Prangey Prangey by J. andJourdan and Niel Niel and (Fig- (Figurebasedure 12b). on12b). Prangey (Figure 12a); and another with details drawn by Prangey and Niel (Fig- ure 12b).

(a) (b) Figure 12. Girault de Prangey:(a )(a ) General plan and section and details from the Mosque(b) (Jourdan, dib.; Bury, eng.); (b) FigureFigure 12.MosqueGirault 12. Girault details de Prangey: (Prangey,de Prangey: ( adib.;) General(a) Niel, General dib.; plan plan Bury, and and sectioneng.). section Source: and and details Monuments details from from the anciens the Mosque Mosque et modernes... (Jourdan, (Jourdan, dib.;c. dib.; 1845. Bury, Bury, eng.); eng.); (b) (b) MosqueMosque details details (Prangey, (Prangey, dib.; dib.; Niel, Niel, dib.; dib.; Bury, Bury, eng.). eng.). Source: Source: Monuments Monuments anciens anciens et et modernes modernes...... c.c. 1845.1845.

2.2. Obtaining the Point Cloud A point cloud has been obtained from the area of the Mosque-Cathedral enlarged by Al-Hakam II, in which Girault de Prangey drew his views. Two laser scanners from the Department of Graphic Expression in Architecture and Engineering of the University of Granada, Leica C10 and Leica BLK360, have been used, with the following speciﬁcations: Leica C10 (Figure 13a): It has a double axis compensator for levelling with an accuracy of 1”, while the 3D positioning of a point is performed with an accuracy of 6 mm. It has a laser plummet that allows stationing on a predetermined point on the ground. It can scan a 360◦ horizontal ﬁeld of view and a 270◦ vertical one. Its spatial resolution is variable: medium resolution implies capturing points every 10 cm, assuming a plane is 100 m away, while the high resolution would imply 5 cm at 100 m. ISPRS Int. J. Geo-Inf. 2021, 10, x 10 of 22 ISPRS Int. J. Geo -Inf. 2021, 10, x 10 of 22

2.2. Obtaining the Point Cloud 2.2. Obtaining the Point Cloud A point cloud has been obtained from the area of the Mosque-Cathedral enlarged by A pointAl cloud-Hakam has II, be inen whichobtained Girault from dethe Prangey area of thedrew Mosque his views.-Cathedral Two laserenlarged scanners by from the Al-Hakam DepartmentII, in which Giraultof Graphic de Prangey Expression drew in hisArchitecture views. Two and laser Engineering scanners fromof the the University of DepartmentGranada, of Graphic Leica Expression C10 and Leicain Architecture BLK360, have and beenEngineering used, with of thethe Universityfollowing specifications: of Granada, Leica C10Leica and C10 Leica (Figure BLK360, 13a): haveIt has been a double used, axiswith compensator the following for specifications: levelling with an accu- Leica C10racy (Figure of 1”, while 13a): theIt has 3D a positioning double axis of compensator a point is performed for levelling with with an accuracy an accu- of 6 mm. It racy of 1”, whilehas a laserthe 3D plumme positioningt that allowsof a point stationing is performed on a predetermined with an accuracy point of on 6 mm.the ground. It It can has a laser plummescan a 360°t that horizontal allows stationing field of view on aand predetermined a 270° vertical point one. on Its thespatial ground. resolution It can is variable: scan a 360° horizontalmedium resolution field of view implies and capturinga 270° vertical points one. every Its spatial 10 cm, resolution assuming isa plane variable: is 100 m away, medium resolutionwhile the implies high resolution capturing would points implyevery 105 cm cm, at assuming 100 m. a plane is 100 m away, while the high resolutionLeica BLK360 would (Figure imply 13b) 5 cm: This at 100 scanner m. is not able to be levelled or stationed, but it ISPRS Int. J. Geo-Inf. 2021, 10, 181 11 of 24 Leica BLK360has a 360° (Figure scanning 13b) field: This of scanner view similar is not toable the to C10. be levelledThe spatial or stationed, resolutions but for it positioning has a 360° scanningpoints in field 3D are of view20 mm, similar 10 mm to the and C10. 5 mm The at spatial 10 m, whichresolutions are referred for positioning to as low, medium points in 3Dand are high 20 mm, resolution, 10 mm respectively.and 5 mm at 10 m, which are referred to as low, medium and high resolution, respectively.

(a ) (b) (a) (b) Figure 13. ScannersFigure used 13. Scanners to obtain used the point to obtain cloud: the (a point) Leica cloud: C10; ( (ba)) Leica Leica BLK360. C10; (b) LeicaSource: BLK360. Own photographs. Source: Own Figure 13. Scanners used to obtain the point cloud: (a) Leica C10; (b) Leica BLK360. Source: Own photographs. photographs. The C10 scanner was used to establish the reference system and level the entire point TheLeica C10cloud scanner BLK360 model. was (Figure To used do 13 this,tob): establish Thisit was scanner stationed the reference is not at point able system to mq1 be and levelledand level the orthemihrab stationed, entire nave point butwas it oriented cloudhas model. a 360as◦ Toscanningthe do X axis.this, ﬁeld Withit was of this view stationed orientation, similar at topoint thea target C10.mq1 wasand The spatialtheplaced mihrab resolutions(Figure nave 14a) was for on oriented positioning the mq7 point, the as thepoints X axis. incoordinates 3DWith are this 20mm, orientation,of which 10 mm were anda target obtained 5 mm was at placedby 10 m,radiation which(Figure with are 14a) referred the on C10the to mq7from as low,point, its station medium the in mq1— coordinatesand highsimultaneously, of resolution, which were respectively. obtaineda scan was by obtained radiation with with the the C10 C10 at frommq1. its station in mq1— simultaneously,The C10 Toa scanner scan link was the was Royalobtained used Chapel, to with establish thelocated C10 the referenceaton mq1. a higher system level, and in the level same the entirecoordinate point system, cloudTo link model.the the C10 Royal To was do Chapel,this, station it was edlocated at stationed mq7 on and a higher at oriented point level, mq1 at in andmq1 the thewith same mihrab an coordinate error nave of was4 system,mm, oriented after which it the asC10 the was Xperformed axis.station Withed aat thisscan. mq7 orientation, Three and oriented additional a target at freemq1 was scans with placed werean error (Figure carried of 4 14 outmm,a) in on afterthe the Royal which mq7 Chapel, point, it which performedthe coordinates awere scan. recorded Three of which additional automatically were free obtained scans with werethe by radiationCyclone carried Register out with in the 360 Royal C10 software, from Chapel, its resulting stationwhich in in an error weremq1—simultaneously, recordedof 4 automaticallymm in all the a scan withlinks. was the The obtainedCyclone distribution Register with theof the 360 C10 stations software, at mq1. is shownresulting in inFigure an error 14b. of 4 mm in all the links. The distribution of the stations is shown in Figure 14b.

(a ) (b) (a) (b) Figure 14. (a) Target used to give coordinates and get orientation (b) links between scan stations. Source: Own images. FigureFigure 14. ( 14.a) Target(a) Target used used to give to give coordinates coordinates and and get getorientation orientation (b) (linksb) links between between scan scan stations. stations. Source: Source: Own Own images. images.

To link the Royal Chapel, located on a higher level, in the same coordinate system, the C10 was stationed at mq7 and oriented at mq1 with an error of 4 mm, after which it performed a scan. Three additional free scans were carried out in the Royal Chapel, which

were recorded automatically with the Cyclone Register 360 software, resulting in an error of 4 mm in all the links. The distribution of the stations is shown in Figure 14b. The remaining scans were performed with the BLK360, carrying out four itineraries. They all started their registration using the C10 scan stationed at the mq1 reference. Figure 15a shows the baseline and the scans recorded by the C10 (colour yellow) and the four traverses by the BLK360 (colour white). These traverses refer to the surroundings of Villaviciosa Chapel and the mihrab central nave (traverse 1), two lateral naves (traverses 2 and 3) and the mihrab (traverse 4). ISPRS Int. J. Geo-Inf. 2021, 10, x 11 of 22

The remaining scans were performed with the BLK360, carrying out four itineraries. They all started their registration using the C10 scan stationed at the mq1 reference. Figure 15a shows the baseline and the scans recorded by the C10 (colour yellow) and the four traverses by the BLK360 (colour white). These traverses refer to the surroundings of Vil- laviciosa Chapel and the mihrab central nave (traverse 1), two lateral naves (traverses 2 ISPRS Int. J. Geo-Inf. 2021, 10, 181 12 of 24 and 3) and the mihrab (traverse 4). Figure 15b shows a view where the locations of the scans are represented by spheres; the whole point cloud was built from those scans.

(a) (b)

FigureFigure 15.15.Scan Scan trajectories. trajectories. (a )(a General) General plan; plan; (b) interior(b) interior view view (the spheres(the spheres mark themark scanner the scanner positions). positions). Source: OwnSource: images. Own images. Figure 15b shows a view where the locations of the scans are represented by spheres; the wholeAll the point scans cloud were was performed built from with those medium scans. resolution, which means a separation betweenAll the captured scans werepoints performed of 1 cm at witha distance medium of 10 resolution, m. which means a separation betweenThe capturedrecords made points with of 1 cmthe atBLK a distance360 scanner of 10 have m. been processed with Recap, and theirThe quality records measurements made with have the BLK360 been obtained scanner using have the been foll processedowing parameters: with Recap, overlap and their(common quality volume measurements percentage have between been obtainedthe reference using scan the and following the registered parameters: one), overlapbalance (common(amount of volume data captured percentage in the between three orthogonal the reference directions scan and of the space registered and how one), much balance these (amountdirections of have data capturedinfluenced in the the constriction three orthogonal of the directions registered of scan) space and and percentage how much points these directionswith an error have below inﬂuenced 6 mm the(between constriction the reference of the registered scan and scan)the registered and percentage scan). Table points 1 withshows an a errorquality below summary 6 mm obtained (between for the each reference of the scantraverses and thecarried registered out with scan). the BLK. Table 1 shows a quality summary obtained for each of the traverses carried out with the BLK. Table 1. Summary of the quality obtained in the four itineraries carried out with the BLK360 scan- Tablener. 1. Summary of the quality obtained in the four itineraries carried out with the BLK360 scanner.

TraverseTraverse Overlap Overlap Balance Balance % % < <66 mm 1 162.5855 62.5855 53.9155 53.9155 99.3852 99.3852 2 58.1112 54.1019 99.9587 2 58.1112 54.1019 99.9587 3 56.9395 55.7934 99.9459 3 56.9395 55.7934 99.9459 4 62.9627 49.9022 99.2762 4 62.9627 49.9022 99.2762 2.3. The 3D Model Geometric Construction 2.3. The 3D Model Geometric Construction The 3D digital model of the building’s current state has been made by importing the pointThe cloud 3D to digital CAD model as a reference. of the building’s To define current the geometry, state has orders been made have by been importing used to theob- pointtain lines cloud or to edges, CAD as well a reference. as planes To and deﬁne intersections the geometry, from orders said havecloud. been used to obtain linesTo or edges,draw it, as the well geometric as planes charact and intersectionseristics of the from architectural said cloud. elements that make up the monumentTo draw it, have the geometric been analysed. characteristics Having ofa deep the architectural understanding elements of these that elements make up is thevery monument important haveto undertake been analysed. the simplification Having a deep or graphic understanding synthesis of of these a large elements building, is veryconsidering important the torelevant undertake scales the or simpliﬁcationdetails. or graphic synthesis of a large building, consideringFirst, recurring the relevant elements scales or (arches, details. capitals, etc.) were drawn as the basis for the graphicFirst, construction recurring elementsof the whole (arches, building. capitals, For etc.)this, the were representation drawn as the criteria basis forused the in graphicimportant construction drawings of of the the 19th whole century building. were reviewed: For this, theAcademics representation (1787; 1804) criteria [12], used La- inborde important (1812) drawings[14], Murphy of the (1813) 19th [ century15], Parcerisa were reviewed:(1855) [21] Academics and “Los Monumentos (1787; 1804) [ 12Ar-], Labordequitectónicos (1812) de [ 14España], Murphy” (1852 (1813)–1881) [ 15[22].], Parcerisa The graphic (1855) conventions [21] and “Losin drawings Monumentos of the Arquitectónicos de España” (1852–1881) [22]. The graphic conventions in drawings of the 20th century [23] and others made with a computer in the 21st century [30] have also been reviewed, considering the interests of the authors and the scale of each drawing. In addition, the proportion theories of Rafael de la Hoz have been considered (1924– 2000). After studying the Mosque-Cathedral and other Arabic designs in Cordoba, Rafael de la Hoz detected the repeated appearance of the number 1.306562964876 ... , which he called the “Cordovan proportion” [67,68]. ISPRS Int. J.ISPRS Geo-Inf. Int. 2021 J. Geo, 10-Inf., x 2021, 10, x 12 of 22 12 of 22

20th century20th [23] century and others [23] and made others with made a computer with a computer in the 21st in century the 21st [30] century have [30]also have been also been reviewed,reviewed, considering considering the interests the ofinterests the authors of the and authors the scale and ofthe each scale drawing. of each drawing. ISPRS Int. J. Geo-Inf. 2021, 10, 181 13 of 24 In addition,In addition,the proportion the proportion theories of theories Rafael ofde Rafael la Hoz de have la Hoz been have considered been considered (1924– (1924– 2000). After2000). studying After studyingthe Mosque the- CathedralMosque-Cathedral and other and Arabic other designs Arabic in designs Cordoba, in Cordoba, Rafael Rafael de la Hozde detected la Hoz detectedthe repeated the repeatedappearance appearance of the number of the 1.number306562964876 1.306562964876..., which..., he which he called thecalled “Cordovan the “AllCordovan proportion this has facilitatedproportion” [67,68]. the ” construction[67,68]. of simple modules as the digital model basis. Over- All this hasAlllapping facilitated this has the facilitated grouping the construction of the modules construction of onsimple the pointof modules simple cloud modulesas revealed the digital as that the model there digital are basis. smallmodel deformations basis. OverlappingOverlapping thedue grouping to restorations the grouping of modules or repairs of moduleson over the centuriespoint on the cloud (Figurepoint revealed cloud 16a). The revealedthat workflow there that are was theresmall simplified, are small equalis- deformationsdeformations dueing to all restorations the due modules to restorations or with repairs dimensional or over repairs centuries differences over centuries(Figure of less 16a). (Figure than The 2% 16a).workflow (Figure The workflow 16 wasb). This was accuracy simplified,simplified, equalisingdegree equalising isall far the superior modules all the to moduleswith that requireddimensional with indimensional the differences schematic differences of perspectives less than of less2% that (Fig-than are 2% to be (Fig- overlaid ure 16b). Thisure 16b) acwithcuracy. This Prangey’s acdegreecuracy perspectives.is degreefar superior is far tosuperior that required to that inrequired the schematic in the schematic perspectives perspectives that are tothat be overlaidare to be withoverlaid Prangey with’ sPrangey perspectives.’s perspectives.

(a) (a) (b) (b) Figure 16.Figure DetailFigure 16.from Detail 16.theDetail Alfrom-Hakam fromthe Al theII- Hakamexpansion Al-Hakam II expansion in II expansionthe Mosque in the in theof Mosque Cordoba: Mosque of of(Cordoba:a Cordoba:) Overlapping (a (a) )Overlapping Overlapping between the between between geometric thethe geometric geometric model model andmodel the pointand and cloud; the the point point (b) cloud;3Dcloud; geometric ((bb)) 3D3D geometricgeometricmodel derived model from derived the point from cloud the point point (view cloud cloud from (view (view bottom). from from Source: bottom). bottom). Own Source: Source: images Own Own. images images..

2.4. Location2.4 .of Location Viewpoints2.4. Location of Viewpoints and of ViewpointsHorizon and lines; Horizon and Prangey Horizon lines;’s Lines;Prangey Viewpoints Prangey’s’s Viewpoints and Viewpoints3D Model and 3D Overlapping and Model 3D Model Overlapping Overlapping The viewpointsThe viewpointsThe were viewpoints identified were wereidentified in an identiﬁed earlie in ran visit inearlie anto earlierrthe visit monument to visit the to monument the and monument from and them from and fromthem them each perspectiveeach perspectiveeach were perspective located were in werelocated the locateddigital in the ingeometric digital the digital geometric model geometric (Figure model model 17), (Figure which (Figure 17), Girault 17 which), which Girault Girault de de Prangeyde indicatedPrangeyPrangey indicated in indicated a schematic in in a aschematic schematicplan of the plan plan building of of the the buildingin building Islamic in times, Islamic as times,times,mentioned asas mentionedmentioned above above (Figureabove 5b).(Figure (Figure 5b). 5b).

Figure 17. Location of Prangey’s viewpoints marked on the current plan. Source: Own image. FigureFigure 17. 17. LocationLocation of ofPrangey Prangey’s’s viewpoints viewpoints marked marked on on the the current current plan. plan. Source: Source: Own Own image. image.

In the mihrab front view (Figure 18a), the viewpoint is centred on the nave with a position close to the ground. The local coordinates are 3505.545 m and 3824.231 m and the viewpoint height is 1.20 m.

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In the mihrab frontIn the view mihrab (Figure front 18a), view the (Figure viewpoint 18a), isthe centred viewpoint on the is navecentred with on a the nave with a position close toposition the ground. close The to the local ground. coordinates The local are coordinates3505.545 m andare 3505.5453824.231 mm andand 3824.231the m and the viewpoint heightviewpoint is 1.20 m. he ight is 1.20 m. ISPRS Int. J. Geo-Inf. 2021, 10, 181 14 of 24 In the mihrab’sIn side the view mihrab with’s side the view forest with of columns, the forest the of local columns, coordinates the local are coordinates are 3500.544 m and3500.544 3811.877 m m; and the 3811.877 height of m; the the viewpoint height of isthe similar viewpoint to the is previous similar tocase the previous case (Figure 18b). (Figure 18b).

(a) (a) (b) (b) Figure 18. Horizon and vanishing lines on the Girault de Prangey perspectives: (a) Mihrab front view; (b) Forest of col- FigureFigure 18. Horizon 18. Horizon and vanishing and vanishing lines lines on the on theGirault Girault de dePrangey Prangey perspectives: perspectives: (a) ( aMihrab) Mihrab front front view; view; (b (b) )Forest Forest of of col- columns umns and mihrab view. Source: Own production. umnsand and mihrab mihrab view. view. Source: Source: Own Own production. production.

In theIn detailed the mihrab’s sideIn the view side detailed viewof the withside mihrab theview forest(Figure of the of mihrab19a), columns, the (Figure vanishing the local 19a), coordinates points the vanishing are outside are 3500.544 points are outside the image.m and The 3811.877 localthe image. coordinates m; the The height local are of coordinates3504.006 the viewpoint m andare is 3504.0063806.937 similar m tom and theand previous 3806.937the viewpoint casem and (Figure height the viewpoint 18b). height is 1.00 m. In theis detailed 1.00 m. side view of the mihrab (Figure 19a), the vanishing points are outside Thethe image.elevated The view localThe fromelevated coordinates the Royalview are fromChapel 3504.006 the has Royal m andtwo Chapel 3806.937vanishing has m points,two and vanishing the and viewpoint the points,local height and the local coordinatesis 1.00 m.are coordinates3504.088 m areand 3504.088 3845.140 m m and and 3845.140 the viewpoint m and heightthe viewpoint is 2.65 m height (Figure is 2.65 m (Figure 19b). 19b).

(a) (a) (b) (b) Figure 19. LocationFigure of horizon 19. Location andFigure vanishing of horizon 19. Location lines and in ofvanishing the horizon Girault lines and de vanishing inPrangey the Girault’s lines perspectives: de in thePrangey Girault (a’)s Sideperspectives: de Prangey’s view of the ( perspectives:a) mihrab;Side view of (a) the Side mihrab; (b) Royal Chapel (view.b) Royal Source: Chapel Ownview view. production of theSource: mihrab; . Own (b production) Royal Chapel. view. Source: Own production.

AfterThe locating elevated theAfter view viewpoints locating from the the in Royal the viewpoints 3D Chapel geometric in has the two model 3D vanishing geometric derived points, model from the andderived point the local from the point cloud,coordinates the interiorcloud, are elevatio 3504.088 the interiorns mthat and appearelevatio 3845.140 inns the mthat andinner appear the elevations viewpoint in the inner of height Prangey elevations is 2.65’s viewpoints m of (Figure Prangey 19’b).s viewpoints were visualised.Afterwere locating It should visualised. the be viewpointstaken It should into account in be the taken 3Dthat into geometric a common account model methodthat a derivedcommon of drawing from method conic the of point drawing conic architecturalcloud, the perspectives interiorarchitectural elevations manually perspectives that is to appear use manually these in the inner is inner to elevationsuse elevations these inner as the of elevations Prangey’s basis for graphic as viewpoints the basis for graphic production.were visualised. Prangeyproduction. sometimes It should Prangey be placed taken sometimes intothe elevations account placed that both the a common elevationsfrontally method in both true frontally ofsize, drawing and in in true conic size, and in otherarchitectural cases, he usedother perspectives a cases,vanishing he used manually point a vanishing for isforegrounds. to use point these for In inner foregrounds.addition, elevations the Inhorizon as addition, the basis line theheight for horizon graphic line height has beenproduction. taken hasinto Prangey been account, taken sometimes which, into account, according placed which, the to elevations the according rules bothof theto frontally theconical rules perspective, in of true the size,conical andis perspective, in is alwaysother located cases, alwaysat he the used draftsman located a vanishing at or the observer pointdraftsman for’s foregrounds.eye or level.observer The In’ svanishing addition,eye level. the pointsThe horizon vanishing are placed line points height are placed has been taken into account, which, according to the rules of the conical perspective, is always located at the draftsman or observer’s eye level. The vanishing points are placed on the horizon line, also considering the angle of view covered in each case. This methodology

facilitated overlapping the 3D model on Prangey’s viewpoints, to assess its accuracy and its level of agreement, as explained below. ISPRS Int. J. Geo-Inf. 2021, 10, x 14 of 22

on the horizon line, also considering the angle of view covered in each case. This methodology facilitated overlapping the 3D model on Prangey’s viewpoints, to assess its accuracy and its level of agreement, as explained below.

ISPRS Int. J. Geo-Inf. 2021, 10, 181 15 of 24 3. Results and Discussion 3.1. Front Perspective of the Mihrab The Prangey mihrab front view fits quite well when overlapped with the digital ge- 3. Results and Discussion ometric model in the interlaced portico arches represented in the foreground (Figure 20) 3.1. Front Perspective of the Mihrab and also in the background. TheHowever, Prangey the mihrab absence front of the view current ﬁts quitegrille is well surprising, when overlapped as it was placed with thethere digital after geometric1741 and drawn model by in theSwinburne interlaced in portico1775-75 arches[13] and represented Lewis in 1833 in the [19]. foreground Today, it (Figure is lower 20 in) andheight also because in the background.it was lowered in the restorations by architect Velázquez Bosco [31].

FigureFigure 20.20. Girault de Prangey (1839): (1839): Digital Digital model model overlapping overlapping the the mihrab mihrab perspective. perspective. Source: Source: Own production. Own production.

However,Among the the details absence located of the on current the edges grille of is the surprising, plate, there as itis was a similar placed view there above, after 1741more and schematic drawn byand Swinburne with a wider in 1775-75 field of [ 13view.] and It Lewisis obvious in 1833 that [19 it]. is Today, not a photographic it is lower in heightview, because because when it was such lowered a wide in field the restorations of view is covered, by architect reality Vel wouldázquez be Bosco distorted. [31]. When comparedAmong with the the details geometric located model, on the it edges is observed of the plate,that the there foreground is a similar arches view are above, fairly moreconsistent, schematic as is the and mihrab with a arch wider (Figure field of 21). view. There It isis obviousa surprising that coincidence it is not a photographic in the height view,of the because columns, when capitals such a and wide the field layout of view of the is covered, arches. reality However, would the be side distorted. arches When of the comparedTreasury and with Sabbath the geometric are poorly model, located, it is observedas they are that on theboth foreground sides of the arches mihrab are but fairly far consistent,apart. It seems as is clear the mihrab that this arch perspective (Figure 21 was). There drawn is a from surprising the arcade coincidence elevation in in the the height fore- ofground, the columns, which was capitals accurately and the measured. layout of the arches. However, the side arches of the TreasuryThis andis of Sabbath great interest are poorly because located, it reveals as they that are the on bothoriginal sides level of theof the mihrab ground but farhas apart.changed It seemsthroughout clear the that history this perspective of the monument. was drawn [11]. fromThe superimposition the arcade elevation of the indraw- the foreground,ings confirms which that the was mihrab accurately environment measured. has maintained its level from 1833 to the present,This after is the of pavement great interest was because replaced it by reveals the architect that the Velázquez original level Bosco of at the the ground beginning has changedof the 20th throughout century. the history of the monument. [11]. The superimposition of the drawings confirms that the mihrab environment has maintained its level from 1833 to the present, after the pavement was replaced by the architect Velázquez Bosco at the beginning of the 20th century.

ISPRS Int. J. Geo-Inf. 2021, 10, x 15 of 22

Figure 21. Girault de Prangey (1839): Digital model (white foreground and red background) overlapping the surroundings of the mihrab. Source: Own production.

3.2. Mihrab Side Perspective Along with the Forest of Columns This interior view of the monument would only be possible if the arcade closest to the draughtsman were removed, so as not to obscure the next arch work. The geometric overlap between the model and Prangey’s drawing is quite similar. Despite the complexity of the frame, there is a certain agreement even in the layout of the most distant planes ISPRS Int. J. Geo-Inf. 2021, 10, 181 16 of 24 ISPRS Int. J. Geo-Inf. 2021, 10, x (Figure 22). 15 of 22

The grille that delimited the mihrab area were also not drawn in this case. The lighting that comes from the skylight that was dismantled by Velázquez Bosco along with the Baroque vaults to recover the Islamic ceiling is also surprising [31]. Other drawings and photographs from the 19th century locate this skylight in the fourth intercolumniation (from the grille) [29], but in Prangey’s image, the light seems to penetrate through the second one, with dubious veracity. The text Prangey included in the plate stated that the width of the 19 parallel naves of the Mosque ranges between 6.35 and 7 meters in the main nave of the mihrab; and between 6.35 and 5.80 metres for the intercolumniation. In other words, the draughtsman took careful measurements to create his drawings. These measured drawings would serve as the basis for this perspective, using a FigureFiguregraphical 21.21. GiraultGirault method dede similar PrangeyPrangey to (1839):(1839): the previous DigitalDigital model model view. (white (white The foregroundelevation foreground o andf and the red redarcade, background) background) which overlap- is over- now pinglappingplaced the obliquely,the surroundings surroundings was of theused of mihrab.the as mihrab. a starting Source: Source: point. Own Own production. The production. digital model and the vanished elevation, which Prangey placed in the foreground, show good correspondence. The careful 3.2. Mihrab Side Perspective Along with the Forest of Columns 3.2.drawing Mihrab of Side the Perspectivebrick pavement, Along whichwith the was Forest replaced of Columns by the current marble pavement at the beginningThisThis interiorinterior of the viewview 20th ofof century, thethe monumentmonument is also of wouldwould interest. onlyonly bebe possiblepossible ifif thethe arcadearcade closestclosest toto thethe draughtsmandraughtsmanHowever, the werewere characters removed,removed, represented soso asas notnot to“toon obscureobscure their knees thethe nextnext” have archarch an work.work. exaggerated TheThe geometricgeometric size in overlapoverlaprelation between betweento the columns. thethe model model This and and error Prangey’s Prangey is frequently’s drawing drawing seen is is quite inquite many similar. similar. contemporary Despite Despite the the engravings, complexity complex- ofitywhic the ofh the frame,invented frame, there scenesthere is ais that certain a certain did agreementnot agreement appear evenin even the in originalin the the layout layout drawings of of the the in most most order distant distant to command planesplanes (Figure(Figuregreater 22visual22).). attention for purely commercial interest. The grille that delimited the mihrab area were also not drawn in this case. The lighting that comes from the skylight that was dismantled by Velázquez Bosco along with the Baroque vaults to recover the Islamic ceiling is also surprising [31]. Other drawings and photographs from the 19th century locate this skylight in the fourth intercolumniation (from the grille) [29], but in Prangey’s image, the light seems to penetrate through the second one, with dubious veracity. The text Prangey included in the plate stated that the width of the 19 parallel naves of the Mosque ranges between 6.35 and 7 meters in the main nave of the mihrab; and between 6.35 and 5.80 metres for the intercolumniation. In other words, the draughtsman took careful measurements to create his drawings. These measured drawings would serve as the basis for this perspective, using a graphical method similar to the previous view. The elevation of the arcade, which is now placed obliquely, was used as a starting point. The digital model and the vanished elevation, which Prangey placed in the foreground, show good correspondence. The careful drawing of the brick pavement, which was replaced by the current marble pavement at FiguretheFigure beginning 22.22. GiraultGirault ofde dethe PrangeyPrangey 20th century, (1839). Digitalis also modelof interest. overlapping the the mihrab mihrab side side and and the the forest forest of of columns.columns.However, Source:Source: theOwnOwn characters production.production. represented “on their knees” have an exaggerated size in relation to the columns. This error is frequently seen in many contemporary engravings, whicTheh invented grille that scenes delimited that did the not mihrab appear area in were the original also not drawndrawings in thisin order case. to The command lighting thatgreater comes visual from attention the skylight for purely that commercial was dismantled interest. by Velázquez Bosco along with the Baroque vaults to recover the Islamic ceiling is also surprising [31]. Other drawings and photographs from the 19th century locate this skylight in the fourth intercolumniation (from the grille) [29], but in Prangey’s image, the light seems to penetrate through the second one, with dubious veracity. The text Prangey included in the plate stated that the width of the 19 parallel naves of the Mosque ranges between 6.35 and 7 meters in the main nave of the mihrab; and between 6.35 and 5.80 metres for the intercolumniation. In other words, the draughtsman took careful measurements to create his drawings. These measured drawings would serve as the basis for this perspective, using a graphical method similar to the previous view. The elevation of the arcade, which is now placed obliquely, was used as a starting point. The digital model and the vanished elevation, which Prangey placed in the foreground, show good correspondence. The careful drawing of the brick pavement, which was replaced by the current marble pavement at the beginning of the 20th century, is also of interest. However, the characters represented “on their knees” have an exaggerated size in relationFigure 22. to Girault the columns. de Prangey This (1839). error Digital is frequently model overlapping seen in many the mihrab contemporary side and the engravings, forest of columns. Source: Own production.

ISPRS Int. J. Geo-Inf. 2021, 10, x 16 of 22

3.3. Side Perspective with Mihrab Detail When superimposing Prangey’s view with the digital model, there is also good correspondence, with small mismatches in the interlaced arches and in the mihrab access arch (Figure 23). The draughtsman would start his drawing from an elevation placed

ISPRS Int. J. Geo-Inf. 2021, 10, 181 obliquely, in a similar way to the previous case. 17 of 24 The then-existing high grille was not drawn either, and in the background, neither the chapel of Santa Teresa nor the altarpiece of the Holy Supper appear, which were represented in a plan from 1741 [22] and were there until 1912. Once again, the draughtsman whichremoved invented elements scenes that thathe would did not have appear thought in the were original not suitable drawings for inthe order place, to as command did other greatercontemporary visual attention draughtsmen. for purely commercial interest. Some inaccuracies and errors in details have been detected, such as decorative circles 3.3. Side Perspective with Mihrab Detail drawn in the upper part, where there are rhombuses, or columns between the interlaced arches,When where superimposing there are pilasters. Prangey’s These viewcolumns with can the be digital found on model, the back there face is of also the goodsame correspondence,portico, which is withslightly small different. mismatches In other in thewords, interlaced Prangey arches used and the inback the elevation mihrab access of the archportico (Figure that 23 is ). not The visible draughtsman from his wouldviewpoint. start Furthermore, his drawing from the size an elevationof the characters placed obliquely,added by inthe a lithographer similar way todoes the not previous correspond case. to the height of the columns.

FigureFigure 23.23. Girault de de Pran Prangeygey (1839). (1839). Digital Digital model model overlapping overlapping the the mihrab mihrab side. side. Source: Source: Own Own production.production.

3.4. RoyalThe then-existing Chapel Perspective high grille was not drawn either, and in the background, neither the chapelThe perspective of Santa Teresa from nor this the elevated altarpiece place of thewas Holy also Supperproduced appear, from whichan oblique were repre-eleva- sentedtion. The in a polylobulated plan from 1741 arch [22 ] and and the were upper there frieze until approximately1912. Once again, mat thech, draughtsman but there are removedsmall mismatches elements that on thehe would right side.have thought The nave were and not the suitable porticoes for the composed place, as by did double other contemporaryarches in the background draughtsmen. show quite good correspondence (Figure 24). Some inaccuracies and errors in details have been detected, such as decorative circles drawn in the upper part, where there are rhombuses, or columns between the interlaced arches, where there are pilasters. These columns can be found on the back face of the same portico, which is slightly different. In other words, Prangey used the back elevation of the portico that is not visible from his viewpoint. Furthermore, the size of the characters added by the lithographer does not correspond to the height of the columns.

3.4. Royal Chapel Perspective The perspective from this elevated place was also produced from an oblique elevation. The polylobulated arch and the upper frieze approximately match, but there are small mismatches on the right side. The nave and the porticoes composed by double arches in the background show quite good correspondence (Figure 24).

ISPRS Int. J. Geo-Inf. 2021, 10, x 17 of 22

ISPRS Int. J. Geo-Inf. 2021, 10, 181 18 of 24 ISPRS Int. J. Geo-Inf. 2021, 10, x 17 of 22

Figure 24. Girault de Prangey (1839). Digital model overlapping the Royal Chapel. Source: Own production.

3.5. Perspective from the Space Near the Mihrab This perspective from the space near the mihrab was published by Prangey in 1841. Again, the section would be used as the basis for the graphic construction. When overlapping the perspective and the digital model, some mismatches can be found, especially in the upper part, which was represented with little height (Figure 25a). When drawing the vanishing lines, it is surprising to see that the height of the horizon line is different at the top and bottom (Figure 25a). In other words, there are two different vanishing points for parallel lines, but according to the rules of conic perspective, they FigureFigureshould 24.24. converge GiraultGirault de in Prangey one. It is(1839). hard Digital Digitalto believe model model that overlapping overlapping this was a the simple the Royal Royal mistake. Chapel. Chapel. Source:It Source: was perOwn Ownhaps production.production.a device, sometimes used by experts in perspective, to get a better view of the space by skilfully manipulating the proportions. 3.5.3.5. PerspectivePerspectiveAlthough fromfrom it is the thenot SpaceSpace a perspective, NearNear thethe MihrabMihrab the digital model has also been compared with the mihrabThisThis elevation perspectiveperspective (Figure fromfrom 25b). thethe space spaceThere nearnear is enough thethe mihrabmihrab correspondence waswas publishedpublished in the byby arch PrangeyPrangey and initsin 1841.1841.vous- Again,Again,soirs. theThethe sectionsectionheight wouldofwould the columns bebe usedused asandas thethe the basisbasis start forfor of thethe interlaced graphicgraphic construction.archesconstruction. in the domeWhenWhen also overlap-overlap- coin- pingpingcide. thethe However, perspectiveperspective there andand are thethe significant digitaldigital model,model, differences somesome mismatchesinmismatches the sevencan cansmall bebe found,archesfound, especiallylocatedespecially in inthein thethemiddle upperupper frieze, part,part, whichandwhich there was was is represented represented no correspondence with with little little in height heightthe upper (Figure (Figure part. 25 25a). a).This confirms that data collectedWhen in drawing elevated the areas vanishing were carried lines, it out is surprising with some to difficulty see that theand height little rigour. of the horizon line is different at the top and bottom (Figure 25a). In other words, there are two different vanishing points for parallel lines, but according to the rules of conic perspective, they should converge in one. It is hard to believe that this was a simple mistake. It was perhaps a device, sometimes used by experts in perspective, to get a better view of the space by skilfully manipulating the proportions. Although it is not a perspective, the digital model has also been compared with the mihrab elevation (Figure 25b). There is enough correspondence in the arch and its voussoirs. The height of the columns and the start of interlaced arches in the dome also coincide. However, there are significant differences in the seven small arches located in the middle frieze, and there is no correspondence in the upper part. This confirms that data collected in elevated areas were carried out with some difficulty and little rigour.

(a) (b)

FigureFigure 25. 25.Girault Girault de de Prangey Prangey (1841 (1841 and and 1839): 1839): (a ()a Digital) Digital model model overlapping overlapping the the mihrab mihrab annexed annexed to to the the mihrab. mihrab. Duplicity Duplicity inin horizon horizon and and vanishing. vanishing. (b ()b Mihrab) Mihrab section section overlapping overlapping the the current current section. section. Source: Source: Own Own production. production.

When drawing the vanishing lines, it is surprising to see that the height of the horizon line is different at the top and bottom (Figure 25a). In other words, there are two different vanishing points for parallel lines, but according to the rules of conic perspective, they should converge in one. It is hard to believe that this was a simple mistake. It was perhaps a device, sometimes used by experts in perspective, to get a better view of the space by skilfully manipulating the proportions. Although it is not a perspective, the digital model has also been compared with the mihrab elevation(a) (Figure 25b). There is enough correspondence in(b the) arch and its voussoirs. The height of the columns and the start of interlaced arches in the dome also Figure 25. Girault de Prangey (1841 and 1839): (a) Digital model overlapping the mihrab annexed to the mihrab. Duplicity in horizon and vanishing. (coincide.b) Mihrab However,section overlapping there are the signiﬁcant current section. differences Source: in Own the seven production. small arches located in the

ISPRS Int. J. Geo-Inf. 2021, 10, x 18 of 22

ISPRS Int. J. Geo-Inf. 2021, 10, 181 3.6. Details and Decoration 19 of 24 Although this work focuses on perspectives, various architectural and decorative details published by Prangey have also been verified for accuracy. This gives a general idea about the accuracy, since they surely served as a basis for the graphical construction of aboutmiddle the frieze, accuracy, and theresince is they no correspondencesurely served as in a thebasis upper for the part. graphical This confirms construction that data of the perspectives. thecollected perspectives. in elevated areas were carried out with some difficulty and little rigour. Let us take into account that the details were published by the artist in 1839, 1841 and around3.6. Details 1845, and sometimes Decoration as elevations and sometimes as perspectives. In this section, some details of 1839 are presented. They have been grouped according to their location, most detailsAlthough of 1839 are this presented. work focuses They on have perspectives, been grouped various according architectural to their andlocation, decorative most corresponding to the mihrab (Figure 26) and the Royal Chapel (Figure 27). First, they have correspondingdetails published to the by mihrab Prangey (Figure have also26) and been the verified Royal Chapel for accuracy. (Figure This 27). First, gives they a general have beenidea aboutidentified the accuracy,on photographs, since they and surely then, servedthey have as a been basis compared for the graphical with the construction orthogonal projectionof the perspectives. of the point cloud, which is provided here as a reference for their location. TheLet usaccurate take into representation account that of the the details perspectives were published is surprising. by the This artist suggests in 1839, that 1841 they and couldaround have 1845, been sometimes drawn on as a elevations true scale. and That sometimes is what Owen as perspectives. Jones and other In this architects section, somewho drewdetails ornaments of 1839 are of presented.the Alhambra They in have those been years grouped would have according done, to using their tracing location, papers, most manycorresponding of them preserved to the mihrab in the (Figure Patronato 26) and de thela Alha Royalmbra Chapel archives (Figure [69]. 27 ).A First, camera they lucida have couldbeen identifiedalso be used on photographs,to draw capitals, and then,pilasters they and have other been details, compared although with thethis orthogonal is a mere hypothesis.projection of In the any point case, cloud, the great which effort is provided made and here the as accuracy a reference of these for their details location. as a basis for developing perspectives, when photography did not exist, should be highlighted.

(a) (b)

Figure 26. DetailsDetails inin thethe mihrab: mihrab: (a ()a Point) Point cloud cloud from from laser laser scanner; scanner; (b) Lithographs(b) Lithographs published published by Girault by Girault de Prangey de Prangey (1839). (1839). Source: Own production. (1839).Source: Source: Own production. Own production.

(a) (b)

Figure 27. Details in in the mihrab in the Royal Chapel: ( (aa)) Point Point cloud cloud from from laser scanner; ( (b) Lithographs published published by by Girault de Prangey (1839). Source: Own Own production. production.

The accurate representation of the perspectives is surprising. This suggests that they could have been drawn on a true scale. That is what Owen Jones and other architects who drew ornaments of the Alhambra in those years would have done, using tracing papers, ISPRS Int. J. Geo-Inf. 2021, 10, 181 20 of 24

many of them preserved in the Patronato de la Alhambra archives [69]. A camera lucida could also be used to draw capitals, pilasters and other details, although this is a mere hypothesis. In any case, the great effort made and the accuracy of these details as a basis for developing perspectives, when photography did not exist, should be highlighted.

4. Conclusions It should be remembered that architectural drawing is a discipline situated between art and science, and that perspective is the most widespread representation system in our culture, due to its affinity with natural vision [70]. Since the appearance of perspective in the Renaissance period [71], various instruments that can be considered as antecedents of the daguerreotype were devised to facilitate its complex graphic construction (camera obscura, camera lucida, etc.). The proliferation of photography in the mid-19th century was a revolution similar to the recent arrival of computing and digital imaging. Girault de Prangey has been recognised in recent international exhibitions as a pioneer in the use of photographic techniques to document architecture. His pre-photography perspectives have also been found to be invaluable in researching architectural heritage in this work. There is no known background on the use of digital techniques to assess perspectives from the 19th century and, for this reason, a novel methodology has been proposed here to analyse interior perspectives of the Mosque-Cathedral of Cordoba. These images have hardly been studied, despite their relevance to the understanding of a monument that has undergone many transformations throughout its long history. To assess the views veracity, we must consider the architectural model drawn, the basic rules of perspective, the education and interests of the draughtsman that drew them and the drawings produced by other contemporary authors. A digital geometric model has been created from the point cloud obtained with a laser scanner. It has been necessary to simplify its representation after a careful architectural analysis and after reviewing the graphic conventions in monument drawings from the 19th century to the present day. The overlapping between the Prangey perspectives and the digital model has allowed us to check the accuracy of their framed views. It seems unlikely that the interior perspectives were produced with a camera lucida, an instrument Prangey had used before [46,47]. They also do not seem to be copied from other drawings, such as those published in 1812 by Alexandre Laborde, who did use a camera lucida [25]. It should be remembered that the title of the 1839 publication includes the words “dessinés et mesurés en 1832 et 1833”. Therefore, Prangey would first make plans, sectional elevations and scale details drawn from his own measurements. He would use the metric system, which began to be used in France just a few years before, in a novel way. He would then obtain the perspectives from these initial plans and drawings. The frontal view of the mihrab was derived from the elevations in true magnitude used as the basis of the graphic construction. The other cases are more complex, since, in each one, an elevation was placed in the foreground obliquely, using its own vanishing point. The perspective that Prangey published in 1841 is especially interesting, drawn by Nicolas Chapuy and cleverly manipulated, with two horizon lines, to improve the view of the space represented. Although they are not the central focus of this work, the architectural and ornamental details that would serve as a basis for the perspectives have also been reviewed. The meticu- lousness and great effort required by the artists to produce the perspectives are remarkable. No remarkable errors have been detected from the comparisons between the perspectives and the digital model. Only in elevated areas around the mihrab do some highlighted discrepancies, which would be difficult to measure by hand, appear. Furthermore, the Prangey drawings confirm that the pavement level of the Mosque- Cathedral did not change after the replacement of the brick pieces by the current marble ones, placed at the beginning of the 20th century. The artist drew building elements that ISPRS Int. J. Geo-Inf. 2021, 10, 181 21 of 24

have now disappeared, such as the plaster vaults, which correspond to consulted drawings and photographs from the 19th century. Some reality manipulations should be highlighted; among them, in all the drawings the removal of the grille along with the mihrab is remarkable. The artist, along with other draughtsmen, would probably have regarded it as an unpleasant visual obstacle, and therefore, did not draw it. Prangey drew the skylight illumination located near the mihrab in such a close way that it seems unreal, perhaps to give a more pleasant luminous environment. In addition, the engravers included human characters with a disproportionate and unrealistic size. Prangey’s perspectives are among the most beautiful and accurate representations of the interior of the monument throughout its history, along with those produced by noteworthy 19th century artists, such as David Roberts or John Frederick Lewis. Finally, it should be noted that Girault de Prangey promoted—as a draughtsman and photographer—modern ideas on architectural graphic expression; the visual memories of architecture can be rigorously understood, stored, retrieved, grouped and displayed. He used sound and advanced graphic techniques to discover and spread knowledge on architectural heritage in a methodical and scientiﬁc way.

Author Contributions: Antonio Gámiz-Gordo, Juan Cantizani-Oliva and Juan Francisco Reinoso- Gordo all took part in the entire research process. All authors have read and agreed to the published version of the manuscript Funding: This research has been funded by internationalisation grants awarded to the Instituto Universitario de Arquitectura y Ciencias de la Construcción (IUACC) of the VI Plan Propio de Investigación y Transferencia of the University of Seville. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Not applicable. Acknowledgments: This research has been made possible thanks to the collaboration of the Cabildo de la Catedral de Córdoba. The authors are also grateful for the support from the research group Expregrafica, Lugar Arquitectura y Dibujo (PAIDI-HUM-976); Programa de Doctorado en Arquitec- tura, Instituto Universitario de Arquitectura y Ciencias de la Construcción from the University of Seville; the research group Ingeniería Cartográfica (PAIDI-TEP-164) from the University of Jaén; and the Survey and Modelling Laboratory (SMlab) from the University of Granada. Conflicts of Interest: The authors declare no conflict of interest.

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