Proc Soc Antiq Scot, 128 (1998), 425-440 Recreatin possiblga e RomaFlaviaf o p nnma Britain with a detailed map for Scotland Alastair Strang* ABSTRACT Since the rediscovery of Ptolemy's Geographia, many versions of a map of Roman Britain have been produced from datathe contains.it Former reconstructions, however, takenot accountdid the of variations in longitude scale which are discerned from Ptolemy's records. Two different scales had, in fact, been used by Ptolemy, in addition to other distortions, to accommodate Britain in a world which believedhe one-sixthbe to smaller than actual. reversingBy Ptolemy's procedures thatso his known places registered with their identified locations, possible,was it also, bringto unknownhis places into their optimum relative positions scalablea on map. becameIt clear during this analysis that Ptolemy must have extracted datahis from authoritativean rathermap than from disparate lists or itineraries and it is likely that this would have been of military origin and from the Flavian occupation period. possibleA arrangement beenhas deduced,such hypotheticalfor a map a and Flavian constructed.map This includes of all Ptolemy's data together with some obliged thatwas he or chose omit someto and recorded information periodthe for either priorcontemporaryor to with the Flavian period. INTRODUCTION Despite being subjected to a small amount of corruption over the centuries, the data of Ptolemy's Geographia, for Britain, still provides a remarkable representation of the spatial relationship of the places recorded. Tha providin, is t recognize gw e latitud longitudd ean e scales appropriato t e a map generated from the data and are aware of individual inherent distortions that such a map displays evidens i t I . t from previously published reconstruction f Ptolemy'o ss wa thap e h tma s force emploo dt yvarieta distortionf y o Britis e th f o h creatin p n Islessi ma s . Recognitioghi a f no vita lGeographiae cluth n ei data (whic RichmonA hI d (1922, 288 soughd )ha t without success), namely Ptolemy's alignment ofEboracum, Isurium and Cataractonium directly north of London, allowed Strang (199 19974& o comprehensivelt ) y presen n improvea t d map-projectior fo n Ptolemy's configuration of Britain and Ireland. This clue led to an understanding that Ptolemy had actually employed two different longitude scales in compiling his map and the resultant, improved map-projection is shown here in illus 1. Durin gseriea analysef so s (see Strang 1994, 1997, 199 forthcomingd 8an t becami ) e clear that Ptolemy had been manipulating data which was remarkably precise about spatial relationships and which could have been assembled only by persons with a good knowledge of 1* 9 Troutbeck Crescent, Bramcote, Beeston, NottinghaP 3B 9 mNG 426 | SOCIETY OF ANTIQUARIES OF SCOTLAND, 1998 Britain and Ireland. In the first century AD, there was only one agency capable of generating this quality of data for Britain and that was the Roman military who could co-ordinate legionary, nava traded an l r informatio distancef no bearingd san s between these places. Becaus lace th k f 1 eo of awarenes f longitudo s latitudd ean e referencing, this extensive bod f spatiayo l information would only have been of military use if collated as a map (as opposed to being set out as numerous separate items of information or as itinerary representations) and this we know was ultimately conveye Alexandria.o dt 2 resolutioe Th probleme th f no s associated with Ptolemy's Roman Britain, allowin gdireca t comparison of Ptolemy's data with a modern, scalable map of Britain and Ireland, provided some clues for the projection and scalar-grid parameters to which a pre-Geographia map might have been drawn suitabla : e map-gri rectangulaa n do r projection with convenient horizontad an l vertical likelscalea d ysan referenc epurpose originth s i f thit I eo . s these papeus eo t rclue n si suggesting a hypothetical reconstruction. The data incorporated in such a map would most likely have been pre-Trajanic and to have originate Flaviae th n di n perio occupationf do . Unfortunately, Ptolemy concentrate placen do s defining coastal configuratio less swa interested nan interion di r chorography, other thaa r nfo few places require indicato dt dispositioe eth f tribano l territories orden I . produco t r morea e comprehensiv s beee ha Flavia nt i necessar p nma supplemeno yt e Geographiath t lisf placeo t s with others which Ptolemy may have chosen to omit or which were forced out by map distortions other and havnot s estil whicbeeof lmay nh he aware . This beelishas t n drawn from various complementary literary sources. Other known Flavian sitethosd san e whose Roman namee sar not yet known are included. Roman sites of known names, but without (apparently) Flavian- period historical or archaeological evidence are listed separately together with reasons for their exclusion from the reconstructe showe b t nye thay d ma tmap t somi s thesa ,f eo earlie d eha r use, In addition to this map of Britain a more detailed map of Scotland has been presented. SOME CLUES CONCERNIN GPOSSIBLA E FLAVIA BRITAIF O P NNMA We know of no Flavian military map of Roman Britain existing today, but much of the information may have been available for example to Marinus of Tyre, prior to Ptolemy's Geographia. From our understanding of the distortions which Ptolemy introduced, it has been possibl reverso et procedures ehi thencd san speculato et e abou possibla t e representatioa f no sourc havthay p eetma ma bee contemporariess nhi r availablo m hi archaeologiste o eth t o T . f o , course, it is the locations of places on the map that are of critical importance and the recent analysis has made it possible to insert these with somewhat more confidence than before. Whilst analysin d synthesizinan g g Ptolemy' f Romao p nma s Britain a particularl, y intriguing point was the situation concerning two river mouths (Nabarus = Naver and Tamarus = Tamar) on the far north coast of Scotland and the south coast of England, respectively. These specifio tw c locations, highlighte illun di , seeme1 s havo dt e escaped imposed displacements, although Ptolemy places to east and west of each appear to have been subjected to such adjustments. Now, on a modern map of Britain it is noted that their respective longitudes west of Greenwic e 4°14 4°10'd har an ' , indicating that thes (ano etw d probably well within Flavian tolerances) were regarded as directly north/south of each other at about 4°12', information most probably the result of Roman nautical determination. This then raised the question as to whether these locations could have defined some reference line from a previous map which Ptolemy wished retainee b o t d withi mucs nhi h distorted representation (illus Britaif 1)o Irelandd nan . STRANG: RECREATING A POSSIBLE FLAVIAN MAP OF ROMAN BRITAIN 427 27 28 29 30 31 64 (EANUS HYPERBOREUS 1/kTURACTONIUMQ OCAIAOUM K300UNUM OCEANUS GERMANIC US OCEANUS VERQIONUS WIROCCNIUM I OBRANNOGENIUM PTOLEMrS GEOGRAPHY GREAT BRITAIN AND IRELAND SCALES LATITUDE =62.5 Roman Mile degrer spe e LONGITUDE ENGLAND = 41.67 Roman Mile degrer spe e SCOTLAND and IRELAND = 25.8 Roman MBes per degree 12 17 18 18 20 25 28 LONGITUDE (degrees) ILLU S1 Ptolemy' Romaf o p snma Britai Ireland nan d (after Strang 1994, 300) moderBritaiof The Irelannnand map presentedis illudin showins2, g this Tamar/Naver base line, which seems to conveniently bisect the east/west extent of the map. Clues as to the overall extent of the map come from the consideration of the two longitude grid scales employed in Ptolemy's map (illus 1): 25.8 Rm [Roman miles] per degree for Scotland and Ireland and 41.67 Rm per degree for England (Strang 1997, 20). The larger scale of the southern sectioe birectangulath f no r grid produce ratia s f 41.6o 7 -H 62. = 0.665 7 whics hi virtually identical to the value for Ptolemy's map of Gaul, giving England compatibility of longitude scale with this contiguous map to the south. 428 I SOCIETY OF ANTIQUARIES OF SCOTLAND, 1998 so ILLUS 2 Modern map of Britain with rivers Tamar/Naver baseline STRANG: RECREATING A POSSIBLE FLAVIAN MAP OF ROMAN BRITAIN 429 valur degree pe Th 25.f eo m e8 R longitud e will coursef o , true b ,particulae e on onl r yfo r latitude fino T .d this latitude Ptolemy'r fo , s small-sized world necessars i t i , firso yt t fin cosins dit e by dividing the figure 25.8 by the constant latitude scale (62.5 Rm per degree) which he used. This yields a value of 0.413 giving a latitude angle of 65.62° north. The Ptolemy latitude of London is 54.02° so that the parallel of latitude that we are seeking identifo t y wouldsmals hi n l o ,world , have been (65.62 —54.02 Roma5 x 62.72 ) 5= n mileo st the north of London. On the full-sized world, for which there are 75 Rm per degree, this equates to 9.67° north of London or a true latitude of 51.42 (the actual latitude of London) + 9.67 = 61.09° north, just sufficient to encompass the Shetland Islands (Strang 1994, 95). Has Ptolemy therefore chosen his northern (rectangular) scale to suit the furthest extremity of such a map representing Britain wit hsimilara , erect north/south orientation? A POSSIBLE FLAVIAN SCALE localizeA d militar woulp yma concernee db d with relative distanc directiod ean n (bearingf o ) locations and would not, at this early stage of cartographic development, be concerned with longitude/latitud worlr eo d context.