New answers tagged land-survey
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Specifically concerning the Finnish Basic Map 1:20000 I found the following (from Suomen peruskartoitus 1947-1975, p. 41):
A photomap prepared from aerial photographs is usually compiled to serve as a base for mapping at a scale of 1:10 000. The mapping is carried out at 1:10 000 using a quarter of the map sheet, 5km x 5km, as a working unit. [...] The ...
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I do know that the Canadian National Topographic Survey (NTS) maps were originally based on air photos flown post WWII in the 1950's. The NTS maps are 1:50 000, and most of the air photos are 1:10 000 or 1:20000. Because air photos do not have a consistent scale across the picture due to radial distortion, the photos are ortho corrected, and then ground ...
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