Lyle, n his contribution to this thread (Reply 7 on 20 December at 1205) posted the following quotation from a statement he had received from the Ordnance Survey:
Contours 1:50 000 (1 to 50,000) aka LandRanger maps:
Metric contours at 10 metre vertical interval are shown on all Landranger maps. They are shown in screened orange. See “Screens” etc specification. Contours are derived from the following sources:
• Contours surveyed at 1:10 000 scale and at 10m vertical interval.
• By interpolation from contours surveyed at 1:10 560 scale which are at 25ft vertical interval.
(The following sheets in Northern Scotland still contain interpolated contours: 10, 11, 12, 15, 16, 17, 18, 19, 20, 22, 23, 24, 25, 26, 32, 33, 34, 35, 36, 39, 41 and 42).
• Field Revision.
• Development plans
I knew that the legend on the latest edition of these maps stated that contours were derived from 1:10,000 maps and I speculated that Lyle might have been sent out-of-date information. So I contacted the OS and received the following reply:
Contours on OS Landranger Maps
I can confirm that the contour information on most OS Landranger Maps is derived from our 1:10 000 scale data. However, a few maps still contain interpolated contours, derived from the old 1:10 560 scale mapping. The note explaining this was removed from the legends in the mid-nineties, which was when the legends were produced digitally. This was mainly because the legends were also revamped to cater for new features that were added to the mapping, thus requiring additional space within the legend. The area of the legend could not be expanded, so selected information had to be excluded from the legend instead.
So it was lack of space that required the OS to provide incorrect information on a few of its Landrangers!
I doubt whether this has any significance for micronavigators.
Hugh
The proper pursuit of accuracy should not be confused with pedantry. Horace