Cartometrics

Cartometrics, which involves the detailed assessment of the mathematical structure (geodetical accuracy) of a map, is still in its infancy as a potentially powerful tool in the historical study of early maps. The modern emphasis on understanding the social context from which a map emerged does not in any way exclude the need to understand also the technical processes of map production, compilation, and/or surveying. The matter of the map as physical artifact, and the medium on which its is drawn or printed, the inks and colors used, the nature of the paper, its dating by watermark or other means, is a separate, but no less legitimate, concern, but questions such as the nature of the projection, the use of triangulation, and the nature of that process (whether it was a purely local system, as in the case of most sixteenth and seventeenth century English county maps, or whether it was linked to a geodetic baseline) are still essential issues to be resolved, as they are also in the case of early charts for navigation: how were these compiled and was any projection involved? What instruments were used, how were they used, and what were their limitations? All such questions rest on the matter of the accuracy of the mathematical map (wrongly assumed to be the sole criterion of cartographical accuracy) and on the calculation of a map's geodetic errors. The arrival of digital cartography greatly increased the number of calculations that could be realistically done for each map, and the ease with which the distortion grids created by cartometric analysis can be applied to early maps, together, or instead of the vectors and circles used in predigital days. At present, though, cartometrics not only has technical problems to resolve (e.g., different programs are likely to produce different results even from the same map) but also, and more importantly, has yet to refine its approach to the selection of historical data or identification of a specific historical problem.