Summary and Conclusions
The techniques described here based on errors of location and the spelling of selected place names have proved sufficiently robust to indicate several relationships between maps which are substantiated by separate historical evidence. This suggests that other previously undocumented relationships recognised with these techniques may also be correct.
Table 1 provides a summary of the errors associated with the maps. Relationships between maps were also investigated. The extent to which pairs of maps shared similar errors of location for selected features was used to assess the closeness of their relationship. Similarities in the spelling of selected place names were also used as indicators of a common origin. Details of these techniques are given in the Methods section.
Fig 2 shows the relationships between the maps of Orkney published between 1550 and 1890 as indicated by these techniques. Arrows indicate links between maps. The red figure beside a map name shows the estimate of overall error for that map. That beside an arrow joining two maps indicates the percentage agreement between the errors of those maps.
Although inheritance of cartographic information between maps can only follow chronological order, this order is not of itself a good guide to the antecedents of maps. Thus Mackenzie’s map preceded that by von Reilly by forty years but the latter was actually a copy of Blaeu’s map published nearly one hundred and forty years earlier.
The development of the cartography of Orkney has not been a smooth progression through time but has depended on a relatively few surveys and their associated advances in surveying techniques. Thus, Pont (circa 1590) appears to have based his map on a personal survey possibly unaided by even a compass. Collins (1690) surveyed with compass and chain and then Mackenzie (1750) introduced the principle of triangulation. After this, increased accuracy appears to have depended on government sponsored surveys by firstly the Admiralty and then the Ordnance Survey based more on superior instruments than on any new technique.
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I wish to express my sincere appreciation of all the help given to me by Mr. C. Fleet, Map Library, National Library of Scotland. Many of the maps referred to here can be seen in greater detail on the Map Library website at www.nls.uk/collections/maps/index.html . I was also greatly helped by Dr. J. Stone, Dept. of Geography, University of Aberdeen and by the staff of the The Orkney Library, Kirkwall. Finally I am grateful to my wife for very valuable assistance with the layout of this site.