Dear All,
North Yorks has been plotting some SAMs based on the MPP mapped 1:10,000 raster maps. This accords with MIDAS and other meta-data standards, but some of the non-MPP'd SAMs are mapped at 1:2,500 scale, as are Battlefields and Historic Parks & Gardens. So immediately, there are two different standards of accuracy of mapping. And comparing these to OS Vector data which has an accuracy of + or - 2 m in lowland areas and 4 m in upland areas will cause problems. That's why I suggested that it might be more sensible for EH to plot boundaries using digital aerial imagery with integrated DTM following the written description of the boundary (the legally binding and definitive bit) in the monument description. This boundary could be plotted at an agreed, standard scale. And it would be more robust in terms of the existing layout of topographical features, i.e. context. It seems to me that it is the integrity / coherence of the topographical context of GIS mapped things that makes them robust, not how accurately (to the nth millimetre) they are mapped.
Cheers,
Neil
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