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Home , Arc measurement, Christopher Hansteen, Struve Geodetic Arc

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Autor(en): Smith, J.R.

Objekttyp: Article

Zeitschrift: Vermessung, Photogrammetrie, Kulturtechnik : VPK = Mensuration, photogrammétrie, génie rural

Band (Jahr): 98 (2000)

Heft 5

PDF erstellt am: 09.10.2021

Persistenter Link: http://doi.org/10.5169/seals-235647

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http://www.e-periodica.ch Histoire de la culture et de la technique

The Struve Geodetic Arc

Since 1994 the International Institution for the History of Surveying and Measurement - a Permanent Institution within FIG -, has been working on a project to get recognition "**B of the Struve Geodetic Arc as a UNESCO World Heritage Site. This arose from a resolution put to the FIG at its 1994 Congress in Melbourne. But what is the Struve Geodetic Arc and what, in this context, is a World Heritage Site? Before answering these questions it is necessary to fill in some of the background to the project and discuss the determination of the parameters of the earth in terms of its size and shape.

Seit 1994 arbeitet die FIG-Arbeitsgruppe Vermessungsgeschichte (heute: International Institution for the History of Surveying and Measurement - a Permanent Institution within FIG) an einem Projekt zur Anerkennung der Meridianmessung vom Schwarzen Meer bis durch Friedrich Georg Wilhelm Struve (Struve Are) als Unesco-Welterbe. Das Projekt entstand aus einer Resolution am FIG-Kongress 1994 1: Friedrich Wilhelm Struve in Melbourne. Der Artikel beschreibt, was der «Struve Are» ist und wie er ein Unesco- Fig. Georg Welterbe werden kann. (1793-1864).

Depuis 1994, le groupe de travail FIG «Histoire de la mensuration» (aujourd'hui: The problem International Institution for the History of Surveying and Measurement - a Permanent Prior to , back to the time of Institution within FIG) s'occupe à élaborer un projet visant à la reconnaissance de la Pythagoras around 500 BC, it had been mesure du méridien entre la Mer Noire et Hammerfest par Friedrich Georg Wilhelm known that the earth was not flat but of Struve, comme héritage mondial de l'Unesco. Le projet est né d'une résolution du some spherical shape. Why spherical was congrès de la FIG de 1994 à Melbourne. L'auteur décrit ce qu'est «Struve Arc» et the next step after flat and not some other comment il peut devenir un héritage mondial de l'Unesco. shape is open to conjecture. At the time however the sphere was considered to be Dal 1994, la Institution for the History of Surveying and Measurement - un'istituzione the perfect shape, perhaps because of its permanente in seno alla FIG - sta lavorando ad un progetto per il riconoscimento regularity in all directions, and could well dell'Arco geodesico di Struve (la misurazione del meridiano dal Mar Nero fino a have been selected in this case just on that Hammerfest effettuata da Friedrich Georg Wilhelm Struve) quale patrimonio dell'umanità, assumption. The fact that it turned out to sotto l'egida dell'UNESCO. Questo mandato è scaturito da una risoluzione del be a correct choice would then, have been Congresso FIG del 1994 a Melbourne. Ma in cosa consiste l'Arco geodesico di Struve e pure luck. cosa si intende - in questo contesto - con patrimonio dell'umanità? Prima di rispondere The problem over the intervening a questi quesiti è necessario spiegare i retroscena del progetto e discutere la centuries has been to determine its exact fissazione dei parametri della Terra, cioè la sua dimensione e forma. shape and size. While it was considered to be a true sphere the problem resolved itself to one of just determining its size, but by the time of Isaac Newton in the might mention Fernel, Picard, the Cassinis, second half of the 17th century even the J. R. Smith Newton, Bouguer, La Condamine, La idea of a true sphere was being Caille, Maupertuis, Delambre, Mechain, questioned. (By «true sphere» and other terms Background Airy, Everest and many others. Notice how mentioned later, is meant the sea level many of these were Frenchmen. surface assumed continuous around the Since the time of Eratosthenes (c276 BC- The focus of this paper is another name, earth. In relation to the overall size of the d 95 BC)thedimensionsof the earth have that of F G W Struve, who made an earth the topography is insignificant). been determined from arc measurements. important contribution during the 19th Why was knowledge of these parameters In fact the theory developed by century. Such was the importance of the work of importance? This can be illustrated simply Eratosthenes remained in use until the era by Struve that it is the hope that some of by saying that if Christopher Columbus of satellite . Many famous names his survey points that still remain can be had known the true size of the earth, in the fields of astronomy, mathematics designated as world heritage monuments. he would not have gone where he did. By and surveying have been involved in the But more of him later. To put his working with a figure that was much too gradual improvement in both techniques, work in context some background detail small he had a distorted idea of the earth equipment and results. Among these one is necessary. he was navigating upon. It was almost as 322 i Mensuration, Photogrammetrie, Génie rural 5/2000 Kultur- und Technikgeschichte

if he thought he was going round a tennis provements even by the late 15th century CK2CUMFEGEMC& ¦4*^.4 c- ball when in fact he was on a football. calculated values of the earth's size varied 3SO ¦ S Not only would he be using incorrect considerably and unfortunately the distances but incorrect directions as well [1 ]. value selected by Columbus was incorrect by about 25%. The measurement difficulty The problem of measuring accurately an /V\ Measure long lines object the size of the earth is not an easy / X One of the difficulties inali the early one yet the principle, first deduced by / /* measurements was that the linear distance Eratosthenes around 230 BC, has remained required had to be physically measured from the basis of all attempts until the advent 1 / Q-/ X end to end by whatever method was felt / of satellites. Although the method / appropriate. Each distance had to be of devised by Eratosthenes was based on the / the order of 60 miles (100 km). If much mathematics of a sphere it was later / / shorter distances only were used the possible to modify it to apply also to shapes •y accumulation of errors in the results would that were not quite true spheres. have been unacceptable. There were no Fig. 2: Principle of determining size of Whatever one is measuring it is advantageous tape measures then as we know them and earth as a sphere. to determine by direct measurement the methods were pacing, knotted ropes, as large a part of it as possible arcs that were not sections of great camel days journeys, the distance before resorting to extending a value by circles. travelled by horsemen in a given time and calculation. One has however to keep within Assuming a , Eratosthenes variations on these. the bounds of practicality. For example, if said that if you measured the linear As far as the angular value was concerned you wanted to measure the circumference distance between two points on a particular this could be found by observing the stars of a football that would be done by line of (also called a meridian or the shadows of obelisks but in either putting a tape measure around it. If on line as, for example, that of zero case the results were crude. the other hand it was required to measure longitude through Greenwich), and were the circumference of a large circular then able also to determine the angular The advent of triangulation roundabout it might be more practical to distance subtended at the centre of the It was not until the early 17th century that measure the length of an estimated quarter earth (see figure 2) between the same two a more convenient method, triangulation, of it and multiply the result by four, or points then the radius and other was developed in Holland and better alternatively determine the diameter and parameters of the earth could be easily measuring equipment became available. multiple up by p. When the structure or determined. Such an angle is not as While it still kept to the basic principle of figure involved becomes the size of the inaccessible as it might at first appear as it can Eratosthenes for measuring a very long earth then a small fraction, say 1°, might be found from star observations at each distance now an element of computation be the more practical amount to measure of the two points. The angle determined entered the method. It required a much and then multiply up by 360. This is in represented some fraction of the 360° shorter line to be measured as accurately effect the basis of the method used. circumference and its length was also as possible (a baseline) and the longer known. A simple calculation would then distance calculated by simple geometry. Why a great circle? give the circumference or radius. As is well known, a line of longitude For example, if the angle was 6° then that ETH circles U^PL>.NIO the earth and goes through both would represent 6/360 or 1/60th of the ^PU 3LE. towcaJJÜÄ- 1 poles. Such a line is called a great circle circumference. If in turn the distance \ l°-57 43Ö tolse of the earth. All lines of longitude are of between the same two points was 600 km R2ENGH jS \ \ AOC-S X. \\ \ that form but in the only line that then the circumference would be 600 x / is a great circle and of comparable size is 60 36 000 km. (Of course they did not / ,»A\ N. \\ / the equator. Thus to get the full use kilometres at that time but the idea 57O7Ot0Ä\\ circumference in as simple a way as possible it is the same.) _ / i° 5674« boise was necessary to measure (or calculate) Unfortunately there are many sources of QJJITD„„ \ peau _____—-— the length of a circle or arc of longitude error inherent in such observations, CUENGM or of the equator. (This is rather an over particularly in the angle and distance V 1 troise=2= .95 mebre simplification but can be accepted as the measurements. These in turn were functions basis of what is required). As theory later of the inaccuracies of the equipment and developed so it became possible to use methods of the time. Despite gradual im¬ Fig. 3: Spread of 18th century arcs. Vermessung, Photogrammetrie, Kulturtechnik 5/2000 i 323 Histoire de la culture et de la technique

shape of the earth in that it was finally Delisle published in 1737 [2], a proposal proved to be oblate (slightly flattened at for an arc to be measured through the the poles) rather than prolate (or and embracing some 22° elongated at the poles), as shown in figures 3 of meridian. He stated that «...this set of and 4. The full name of this figure is an degrees when determined would display oblate spheroid. The difference from a in an incontestable manner, if their variations true sphere is small, being only some 20 were uniform, ...would show km between the maximum and minimum whether different meridians have different radii in a total of almost 6400 km. (i.e. curvatures...» Surprisingly the such PPOLATE. only 0.3%), but nevertheless highly Empress of was not frightened by Sz > S significant when navigating. a vast proposal and gave it her backing to But that only solved half the problem. contribute to the progress of science. There was still the matter of an accurate Unfortunately in 1739, after Delisle got value for the size of the earth and this was as far as measuring a base on the ice from complicated by the fact that it was not Peterhof Castle in Kronstad to Doubki now sufficient to do the calculations as if Castle and connecting the base to several it were a perfect sphere. points by triangulation, a journey to Siberia in 1740-41 interrupted his work The size of a non-spherical earth and it was never restarted. To determine the dimensions of an oblate At that time the kilometre had yet to be O&LATE it had and the base had been >S-L spheroid (or a prolate one if turned developed actually out to be that shape), requires the accurate measured as about 20 verstes, an old Fig. 4: Oblate or prolate? determination of at least two long Russian unit of approximately 1.067 km arcs as widely separated in latitude as per verste. The measurement itself was by The angles were measured by instruments possible. The various pre 19th century arcs in wooden bars of known length placed end such as quadrants and later, theodolites. the list above were all useful but they did to end. Nothing was published on this Essentially the solution revolved around throw up difficulties not least the effects work but in 1844 Otto Struve, son of F G the fact that from a chain of triangulation of large mountain masses on the true W Struve, did come across Delisle's it was possible to determine the distance position of a plumb bob, universally used to manuscript in the Paris Observatory archives. between a point at each end of the chain level observational instruments. It was [3] For his angles Delisle talked of using a [1]. proved during the 18th century survey 30° sector of 12-15 ft radius and a quadrant work in Peru that if a plumb bob is hung of 2-3 ft radius. The «true» shape in the vicinity of a large mountain mass Both theory and practical results then it is pulled (or attracted) slightly out suggested that the earth was probably not a of the vertical by that mass. If the plumb true sphere after all but some slightly bob is not vertical then any instrument distorted shape. Ignoring the land elevations that is itself made level (horizontal) by use and sea bottom depressions around the of a plumb bob, will also be out of level world, sea level forms a sensible datum by the same amount as the plumb bob is surface to which everything can be attracted. ' referred and can be treated mathematically Increasingly as further arcs were ¦¦¦

measured ¦ and the so the accuracy improved "'' gg 7> V,«/a""'a Various long triangulation schemes were uses to which the results could be put [t observed, particularly in different parts of required yet greater accuracy. The vicious ¦- France but by the first half of the 18th circle thus required further arcs to be century also in Peru, Lapland, , S Africa measured. More uses were also found for the \ and . During the second half of networks of triangles that resulted, not that century and the early 19th century least the basis of accurate mapping of the other arcs were observed in USA, Hungary, countries concerned. India, , England, , Denmark and . First moves in Russia The arcs in Peru and Lapland during the At about the same time that the Peru and 1730s and 40s settled the problem of the Lapland arcs were being measured Joseph Fig. 5: Struve Arc (detail). 324 i Mensuration, Photogrammetrie, Génie rural 5/2000 Kultur- und Technikgeschichte

Nothing more materialised in that region The selection of route • be the first multi-country arc until 1814 when B A von Lindenau, It is little surprise, since Struve worked at • be the longest arc at that time. Director of the Seeburg Observatory, Dorpat University, that he decided any In the 1860s A R Clarke, made very proposed an arc of meridian on the shores of extensions of his surveys should follow, as extensive inter-comparisons of arcs around the White Sea in North Russia. This did nearly as possible, the line of longitude the world in an endeavour to get the best not progress because of a disagreement (meridian) through Dorpat Observatory. possible overall results for the earth's overwhich instruments-German or Russian Looking at this line on a map it was clear dimensions. The Struve arc featured prominently should be used. Struve'sopinion however that some work had already been done in his calculations and was the was that in any case it was not a good in its vicinity in the far north (by Mauper- longest of the six he used. site for well conditioned triangulation. tuis 1736-37; and by Svanberg 1802-03) Further extensions in the 20th century Enter the subject of this paper, F G W from the top of the Gulf of Bothnia well have resulted in the «Struve» arc nowthe- Struve. into the Arctic Circle. Here was an oretically reaching from near North Cape opportunity to connect to that work and to the Cape of Good Hope. It was 1954 further extend the line. At the same time it when two quite separate arcs - that by The Struve Geodetic Arc became clear that Tenner was working Struve and that started by Gill around Struve and colleagues more or less along the same meridian. 1882 in South Africa which gradually The early 19th century saw the While Struve could envisage the northward worked its way northwards, made a linkup commencement of a very long arc through extension, Tenner similarly noticed feasible. India by William Lambton. On the death of how there could be a southern extension Lambton in 1823 it was continued to its as far as the . Thus the elements The field work completion in the 1840s by George Everest were present for an arc that stretched Bjorn Harsson, speaking at the FIG

so that it extended from the southern from Fuglenaes near Hammerfest in the Congress in Melbourne in 1994 [4] tip of India to the foothills of the far north over some 2822 km (1753.3 summarised Struve's [5] reported division of Himalayas. miles) to Staro-Nekrassowska near Ismail work on the arc in four phases totalling At about the same time F G W Struve, in the south over 25° of latitude. Today seven sections. Professor of Mathematics and Astronomy the line stretches through ten different at Dorpat, was put in charge of a trigonometrical countries. First phase survey in Livonia. This terminated Central West Russia 1816 to 1830 in a baseline on the ice of Lake Werz- Units of length Jerw. This work enabled Struve to interest Although at the time of the surveys, the c 1816 officials in the idea of an arc of about metric system was well established, the The early work by Struve had baselines 3M.° between Högland, an island in the measurements were recorded in the old measured with wooden bars and angles

Gulf of , and Jacobstadt to the French unit of the toise which is approximately by sextant yet even so he got good south. This he was able to observe 1.949 m. Both English and French results. between 1822 and 1827. During more or feet appear in some of the results, where less the same period (1816-1831 another the two different feet varied by a noticeable 1820 surveyor, de Tenner, was doing similar amount with 1 French foot Struve obtained a grant from Dorpat work further south in but at that approximately 1.067 English feet. University to fund further stage he was not operating jointly with including development of his own form Struve. The daunting task of base line equipment He consulted with Once he had completed his early surveys, To even contemplate such a huge scheme Gauss, and decided to adopt the observing Struve was keen to extend the measurements of extensions and collaborations was a method used by Schumacher on the further north and south so that a daunting task in itself. Such an arc would arc between Denmark and Hannover. He very long line would result and could be however: took his reconnaissance northwards to the basis of a sound set of values for the • build upon the previous schemes in Peru Högland but whilst building substantial earth parameters as well as having other and Lapland which basically set out signals he did not leave bolts in the rock uses. He would have been aware of the to prove the shape of the earth but the to mark the positions. work at that time in India and that it would equipment for which was still relatively be an ideal partner to anything he did crude 1822 to 1827 through Russia, to determine the earth's • allow computation of accurate figures Struve fitted observing in between his parameters. (As indicated above, one arc for the earth dimensions lecturing duties. Professor Paucker from on its own is insufficient to determine the • be the first arc to feature in Russian helped with the astronomical parameters of an oblate spheroid.) territory observations at Jacobstadt and Högland. Vermessung, Photogrammetrie, Kulturtechnik 5/2000 i 325 Histoire de la culture et de la technique

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Fig. 6: Monument on Kittisvaara. Fig. 7: Station at Nivavaara.

Struve had already thought of crossing the this time that Tenner began to establish 1844 Gulf of Finland although the connection permanent station marks. A baseline was measured near Elimä (lat. would be difficult. 60°> 50'). Further agreement to extend 1831 the scheme south to the mouth of the River By 1825 Struve obtained permission to extend Danube and its observation by Tenner. Tenner's responsibilities extended into northwards and connect with the Lapland When Tenner passed his results to Struve . He was also authorised by arc and even to extend that to the Arctic. he also included values for the arc that Prince Wolkonsky to carry out an arc He worked with 3 Finnish officers who connected to the Prussian geodetic measurement tied to baselines at Ossownitza had similarly been educated at Dorpat. network, thence to France and the British and Ponedeli. As a result Tenner's most Isles. This was the first major transcontinental northerly point was then only 32 km west 1832 European East-West geodetic of Struve's most southerly station. Angle measures began with measurement framework. in Finland mostly led by Woldstedt. 1828 1845 The possibility of joining the two arcs Astronomical observations were made brought the two astronomers together, near Tornea (lat. 65° 51 ') and at Kilpi-Ma- possibly for the first time, and with it ki (lat. 62° 57'). A further base was notice of the serious problem of scale measured at Uleäborg (lat. 65° 00'). differences. This then allowed a readjustment of the chain from Tornea to Ssuprunkowzi, an Second phase arc of 17° 05' 33" which was later used Extension to the south and north by Bessel in his final determination of the 1830-1845 . This began with Struve requesting resources from the Tsar Nicholas I to extend » Third Phase northwards to Tornea. The idea was to Sweden and 1844 to 1851 connect with the earlier work of Mau- pertuis and the extension of that by Svan- 1844 berg. Struve conferred with scientists from

Meanwhile Tenner was continuing his Norway, Sweden and Russia as well as with geodetic work south of the River Dnestre 1 Tenner, on the possible extension southwards "If Sea northern passing through parts of the . His to the Black and for a baselines at Ossownitza and Staro-Kon- extension to the Arctic. Commissioners stantinow were among the longest in the were appointed by Sweden and Norway whole arc. Astronomical observations to assess the feasibility - Sweden were made at Kremenetz (lat. 50° 06') Fig. 8: Tornea Church. Incorporated in from Tornea to and Norway and Ssuprunkowzi (lat. 48° 44'). It was at the triangulation of Maupertuis. from there to North Cape. Later the same

326 Mensuration, Photogrammetrie, Génie rural 5/2000 Kultur- und Technikgeschichte

year Struve met with King Oscar I and terminal was monumented with a stone proposed the extension to the Barents Sea. block, and small iron bolt at the centre. This was quickly agreed and N H Seiander Bad weather severely delayed the was made responsible. astronomical observations at Fuglenaes and Lindhagen just managed to get the last tf 1845 boat south before the permanent winter Norwegian participation was put in the dark set in. Unfortunately his assistant hands of Christopher Hansteen (1784- Lysander died on the long journey back 1873) Director of the Christiana Observatory. to Pulkovo. There were 15 stations between Hammerfest and the Swedish border

near Kautokeino. The astronomy was ——fw« 1845 at Fuglenaes near Hammerfest because " I 13 June saw agreement between Sweden North Cape itself was unsuitable for the and Norway for the arc to begin. Hansteen final station because of the weather despatched two young officers to reconnoitre conditions and persistent fog. the build and determine area, signals «w- suitable sites for the baseline and 1851 st» astronomy. A baseline was measured near Tornea and the astronomy completed at Stuor-oivi. 1846 to 1850 There were 24 stations in the Swedish Fig. 9: Monument at Fuglenoes in The field observations. section which was mostly observed by Se- Hammerfest. The northern terminal lander, Lindhagen, Skogman and Wagner. of the Struve geodetic arc. 1848-1849 After Tsar Nicholas I gave his assent Tenner Fourth phase cently as 1942 by Izotov and Krassovsky completed the arc southward to Completion 1852 to 1855 in their ellipsoid calculation. Norwegian Ismail Staro-Nekrassowska (lat. 45° 20') Some supplementary reobservation of geodesists repeated the astronomical on the Black Sea. suspect values were made during this observations at Fuglenaes in 1928 with Hans period. To honour the completion of the arc Jelstrup and in 1950 with Yngvar Schiertt. 1850 May monuments were erected at Hammerfest There was good agreement with a variation The Alta base was measured by Klouman and Ismail. in latitude of less than 6m. (1813-1885) and a Swede from Struve's In the 1970s the remains of the training staff at Pulkovo. The area was flat but the Subsequent use base at Pulkovo was recovered and new base was only 1154.71 2251.7 m. Each Data from this arc was used even as re- pillars established at the terminals.

Instrumentation Struve used a universal instrument by Reichenbach of Munich which had a 13 inch diameter horizontal circle and 11 inch vertical circle. These were graduated to 5' and read directly by verniers to 4". Tenner used a variety of seven instruments a of different makers. There v? by range were two repeating circles, one of 13 inches diameter by Baumann which read to 4" by and the other 14.3 inches WËk ~J vernier, by Troughton reading by vernier to 10" A 12 inch diameter terrestrial repetition theodolite by Reichenbach read by vernier to 4", an 8 inch astronomical repetition theodolite by Ertel reading to 10"; a repeating theodolite of 10 inches made in " the Etat-major and reading to 5 ; and two Fig. 10: The old «Fuglenoes Skane» in Hammerfest, with the Struve monument. instruments by Ertel. The first two of these Vermessung, Photogrammetrie, Kulturtechnik 5/2000 i 327 Histoire de la culture et de la technique

instruments gave inclined angles whilst lignes of the Fortin toise at 13°R. For the tact lever which was pivoted to the bar. the other five used by Tenner and that by bases at Alten, Over Tornea and Two thermometers were set into holes in Struve gave horizontal angles direct [3], Taschbunar the standard was of the bars and the bars were each set in 1727.99440 lignes. For the Romankautzi boxes from which their ends protruded. Standards of length base the standard was of 1728.01991 Seven of the baselines were measured The standard unit used was the toise of lignes. The value of Tenner's standard, using this equipment and Struve estimated Paris which was the same as the toise of used for the bases at Ponedeli, Ossownitza the probable errors of each to be around Peru. It was designed by Struve and and Staro-Konstantinow was of 1 ppm constructed by Fortin. From this standard two 945.75779 lignes. [5] The other three baselines were measured field standards were made each of about by equipment devised by Tenner. Here the 2 toise or 1728 lignes long (1 ligne Vu Baselines bars were of forged iron 2 sajènes long inch). Tenner on the other hand used a Sprinkled among the 258 principal triangles One end of each bar was fixed and the standard of 945 lignes which equates to were 10 baselines, five of which were other free to move. At this latter end was the Russian sajène or 1.0946 toise. During measured by De Tenner, three by Struve a sliding scale that could be used to 1850 to 1853 19 different standards and one each by Selander and Hansteen. determine the distance between consecutive were intercompared at Pulkovo. Thus the Struve used four wrought iron bars each bars. relationships become complicated. of 2 toise in length. One end of each bar That used on the baselines of Simonis, had a small cylinder with slightly rounded Results Elimä and Uleàborg was of 1728.01249 end, the other end of each had a con¬ Observations for latitude and azimuth

Dramatis personnae pertuys. After studying in Paris he was in the latitude covering 69° from the West coast A few words about the characters involved French army until 1723 when he became of Ireland to Orsk on the Ural river. He was involved in the French of Sciences. a founder of the Russian are appropriate here. Academy Geographical By 1728 he strongly believed in Newton's Society and belonged to some 40 scientific Hansteen idea on the shape of the earth and began academies, learned societies and the like. Christopher Hansteen was born 26 to work on his own theories and even September 1784 in Christiana (now ) and published a treatise on the figure of the earth Svanberg died in the same city 15th April 1873. He which signalled the beginning of the Jons Svanberg was born 6th July 1771 in studied law at Copenhagen and later establishment of the Newtonian hypothesis in Neder-Kalix, Norrbotten, Sweden, and died became Professor at Christiana. By 1817 as a France. In 1736 he led an expedition to Lapland 15th January in Uppsala. By 1787 he was President of the Geodetic Institute he played to make a measure of a studying at Uppsala University where he was a leading role in the survey of Norway. He and he was later involved in further arc to later become Professor of Mathematics. was particularly interested in geomagnetism measurements in France. In 1745 he accepted During the period 1799-1801 he led a team and magnetic charting. an invitation from Frederick the Great to go that reobserved the work of Maupertuis 60 to the Academy of Sciences in Berlin where earlier at the north end of the Gulf of Lindhagen years he became its President. Bothnia. In doing so he extended the original. Daniel Georg Lindhagen (1819-1906). Was He had a love of decimals (which is a Swedish astronomerwho worked in Pulkovo. Selander evident in the exaggerated accuracy he quoted He spent two years on survey work in Nils Haqvin Selander (1804-1870) Director in his observations) and complicated Lapland. Later he became permanent of the Stockholm Observatory. calculations. secretary to the Royal Academy of Sciences in Stockholm. He married Wilhelm Struve's Struve Tenner daughter Olga. Friedrich Georg Wilhelm Struve was born in Karl Ivanovitsch de Tenner was born 22 June Maupertuis Altona, Germany 15th April 1793 and died 1783 in Narva and died 28 December 1859 Pierre-Louis Moreau de Maupertuis was 23rd November 1864 in Pulkovo, Russia. He in Warschau. He spent much of his working born 28th September 1698 in St Malo and married twice with a total of 18 children. He life on the arc measurement. In 1848 with died on 27th July 1759 in Basel. On 8th graduated in philology from Dorpat in 1810 Zylinski he found earth parameters of a October 1745 he married Eleonore Catherine and started work at the University observatory. 6380 880 m, f 263.597. Tenner devised a von Borck. He was said to have been a spoilt By the age of 20 he became Professor base measurement system using only one child and this resulted in a certain intransigence of Mathematics and Astronomy at Dorpat. bar with temperature obtained from two and unwillingness to be criticised that His involvement in the survey of Livonia was thermometers whose bulbs were inserted later led him into difficulties. His early the start of almost 40 years of work on the into the body of the bar. education was private. His father was ennobled meridian arc. As a result of which, in 1857 by Louis XIV as René Moreau Sier de Mau- he proposed the measurement of an arc of

328 Mensuration, Photogrammetrie, Genie rural 5/2000 m Kultur- und Technikgeschichte

were made at 13 selected stations 4 of A World Heritage would see them being permanently these were in Scandinavia and the other Monument marked and maintained in good order 9 in the Russian states. This gave 12 arcs and access. The authority for this would that could be computed separately. These How then does all this fit into the concept need to come from the national government varied from 1° 22' to 2° 54' in length. of a World Heritage monument? Such department concerned. Considering From these the length of 1° was monuments to date have all been very the age of the points, the difficult determined for each of the 12 arcs and these large structures or features for which the access to the vicinity of many of them and varied from 57 252 t in the far north to area is often measured in many hectares. the difficulty of recovering the ground 57 068 t in the far south but there were With the arc, the area covered by the chain mark, the task of compiling a summary some inconsistencies in between. Using of triangulation is large but the actual survey for submission to UNESCO will obviously seven different divisions there was a more stations are essentially point positions take hard work to complete. regular decreasing pattern between similar only and even with any cairn that covers Those working on the project hope to submit extreme values. some of them the area taken up is but a documentation by June 2000. This is Struve concluded that the overall length few square per point. That does being coordinated by the Survey Department of the meridian arc was 1 447 787 toise not appear to present a problem to the of Finland. The arc passes through (=2 821 854 m) for 25° 20'08.29" or 1° authorities who rather see the unusual that country, and much of the material 57 144 t. concept as a challenge. necessary is available there. Should Combining his results with those of Bessel Today the Struve arc passes through ten UNESCO look favourably upon the idea and gave the ratio of the earth axes as about countries: Norway, Sweden, Finland, and grant the arc World Heritage status, it

293.7 : : 294.7. He did however make the SSR countries of Russia, , would then be hoped to mount a remea- other calculations with varied results. Latvia, Lithuania, Byelorus, Ukraine and suring exercise by GPS at the selected Moldova. Each of these countries contain points and to use that to investigate the a good number of the Struve stations accuracy of the original work. That could except Russia which has only - on the island then lead to further investigative work Summary of Högland in the Gulf of Finland. relating to the original observations. However The arc in total consists of some 265 because of the very limited resources 1830 points plus some ancillary ones in base available at present, progress is one step End of phase one. There was a complete extension networks. Of these a few are at a time rather than opening up on several meridian arc from Högland in the Gulf of already permanently monumented such as fronts at once. Finland (latitude 60° 05') to Beim (latitude those at Fuglenaes in North Norway, Kit- 52° 02') 8° 03' extent. tis in Finland and Staro-Nekrassowka in The Future the Ukraine. The first and last of these If the project should come to a successful 1844 three have inscribed obelisks whilst that conclusion then it would not be impossible End of phase two. There was a complete at Kittis has a form of pyramidal cairn with to extend the idea south into Africa arc from Högland to the Dnestre river inset commemorative plate. and down the 30th meridian to South (latitude 48° 45'). The aim is to select two or three points in Africa. As is indicated by Chovitz & Fischer each of the nine countries, otherthan Russia, in 1956 [6], for purposes of determining 1851 that are recoverable as definite Struve the figure of the earth the arc of the 30th End of phase three. There was a complete positions and to have them marked in meridian was linked across the Mediterranean arc from Fuglenaes to Staro-Nekrassowsa some commemorative manner. Those to European arcs. Thus it could be except for the need to add some selected would be in positions of reasonable an extension of the Struve meridian arc supplementary data and reobserve various access to the public (some in North project to continue through the African suspect stations - which took place during Norway for example require a helicopter arc of the 30th meridian and so preserve the last phase. to achieve access or alternatively several a series of points from the North Cape to The full arc extended over 25° 20' 08.29 " days trek). Port Elizabeth or even along to Cape of latitude with the linear separation of The structure (if any) at the selected points Point. the terminals as 2822 km. When would possibly vary from country to country combined with the observations of Bessel and but each would bear a similar plaque Names with those in India it gave an oblate spheroid giving the briefest of information about In the interval since Struve completed his where the ratio of the major and the arc and the particular point. work many place names have changed. minor axes were approaching 1 in 300, a Each of the countries involved is required Some have simply a change of one or two value which is comparable with that to first of all identify two or three selected letters, others have completely altered acknowledged today. points and then to indicate how they their names. For example: Dorpat Tar- Vermessung, Photogrammetrie, Kulturtechnik 5/2000 i 329 Histoire de la culture et de la technique

tu, Donau Danube, Leningrad St [4] Harsson B G et al., 1994: The Russian-Scan¬ ropäische Gradmessung. Geodeet Nr 6(30) pp Petersburg. The regional names also have dinavian Meridian Arc Measurements 25-27 . FIG Melbourne changed so that, for example, Bessarabia 1816-1852 Congress Kakkun J et al., 1986: Le 250e Anniversaire de Paper TS 101.3. is now Moldova and Livonia has been la Mesure de l'arc du méridien en Laponie. Pub. divided between Estonia and Latvia. [5] Struve F G W, 1860: Arc du méridien de No 103 of Finnish Geodetic Institute. Helsinki. le la Glaciale 25° 20' entre Danube et Mer Kaptjug V B et al., 1996: Struve's arc of the mesure 1816 1850. 2 vol. Acknowledgements depuis jusqu'en meridian agrees with the first GPS results. ZfV St Petersburg. No. 12 572-576. A project such as that for the Struve arc pp [6] Chovitz B & Fischer I, 1956: A New Deter¬ requires co-operation from many people. Torim A, 1994: F G W Struve and the triangulation mination of the Figure of the Earth from of Livonia. Geodeet Nr 6(30) 31-34 Thanks are due to Alan Batten, Jan de pp Arcs. Trans. American Geophysical Union, Tartu. Graeve, Bjorn Harsson, Jane Insley, Vitali Vol 37 No 5 October pp 534-545. Kaptjug, David Wallis, the Finnish Survey Verio A, 1970: The Struvean triangulation Smith J R, Basic An [7] 1988: geodesy. intro¬ stations today (In Swedish). Proceedings of the Department and contacts in all the countries duction to the history and concepts of modern 6th general meeting of the Nordic Geodetic concerned. In particular, Jane Insley geodesy. Landmark Enterprises, Rancho Commission, Helsinki. made many constructive comments on Cordova, California. Verio A, 1990: One and a half centuries from the draft of this paper. the measuring of the Struvean chain. Paper FIG References: Selected further reading: 101.3 Congress Toronto. Batten A H, 1977: The Struves of Pulkovo a Verio A, 1994: Later phases and utilizing of the [1] Smith J R, 1986: From Plane to Spheroid. - of Journal of the Northern part of the Struvean chain. Geodeet Determination of the Figure of the Earth family astronomers. Royal Astronomical. of Canada vol 71 No 5 Nr 6(30) 27-30 Tartu. from 3000 BC to the 18th Century Lapland Society pp October 345-372. and Peruvian Survey. Expeditions. Landmark pp Zakiewicz T, 1997: The African arc of the 30th Enterprises, Rancho Cordova, Batten A H, 1988: Resolute and Undertaking meridian. Paper presented at iKusasa CONSAS California. Characters: The lives of Wilhelm and Otto 97. Durban. [2] DeL'IsleJ-N, 1737: A proposal for the Struve. D Reidei Pub. Co. of Kluwer Academic measurement of the earth in Russia. Phil.Trans. Publishing Group. J.R. Smith Royal Society. Vol XL No 449 p 27. This was Debarbat S, 1990: L'arc géodésique le plus a translation of the original. long: Delisle, Les Struve et l'observatoire de 24 Woodbury Avenue Pulkovo. From Inertial Coordinate Petersfield [3] Butterfield A D, 1906: A history of the System on determination of the figure of the earth from the Sky pp 25-28. J H Leiske and V K Abalakin Hants GU32 2EE Netherlands. arc measurements. Davis Press, Worcester, (eds). England Mass. Dick W R, 1994: Wilhelm Struve and the Eu¬ e-mail: [email protected]

four beauftragt, zunächst die vorhandenen Basel und Umgebung Übersichtspläne der Stadt sowie von Riehen und Bettingen nach genauen 1836-1839 Instruktionen zu einer Kartenvorlage in den Massstab 1:25 000 zu reduzieren. Im Im Verlag Helvetica ist 2000 die Faksimile-Ausgabe der Cartographica anfangs Zeitalter eines vereinigten Europas mag es topographischen die Dufourkarte erschienen. Aufnahme 1:25 000 für erstaunen, dass bereits damals auch Pläne

der benachbarten badischen Grenzgemeinden L'édition facsimile du relevé topographique 1:25 000 de la carte Dufour est au parue beigezogen wurden. début de 2000 dans la maison Cartographica Helvetica. In der hier wiedergegebenen Karte ist ein Teil des Originales von 1836 (Stadt) in All'inizio del 2000 la casa editrice Cartographica Helvetica ha lanciato il rilevamento dasjenige von 1839 (Landschaft) eingesetzt topografico - scala 1:25 000 - della Carta Dufour nel formato facsimile. worden. Praktisch das ganze dargestellte Gebiet war damals bereits vermessen, so Teil der Karte der dass Baader die vorhandenen Katasterpläne H.-U. Feldmann Topographischen Schweiz im Massstab 1:100 000 wandte übernehmen konnte. Dufours sich Guillaume-Henri Dufour 1836 an den Instruktionen entsprechend ist das Terrain Auf der Suche nach zuverlässigen Basler Unter-Bauinspektor Friedrich Baader mit Schraffen dargestellt. Der aufmerksame topographischen Grundlagen für den Basler (1802-1867). Baader wurde von Du¬ Betrachter wird feststellen, dass die

330 Mensuration, Photogrammetrie, Génie rural 5/2000