Cadastral maps
Large-scale plans are initially much more expensive to make per unit area than small-scale maps, but it must always be remembered that, once the large- scale survey has been completed, accurate maps on any smaller scale can be derived from them. The converse is not however true for although larger-scale maps can easily be constructed by using computers, they can never be more accurate than the original data from which they were first compiled.
Usually cadastral maps need only be “planimetric” maps, that is to say, they need not show topographical relief. There may be special reasons why altitudes should be recorded on cadastral maps, but ordinarily all that is needed is a plan of what is seen, without stereoscopy, from a point vertically above the piece of land observed. Distances recorded on such plans are the horizontal distances between points and not the surface distances actually measured on the ground. Thus the area recorded for a plot of land on a steep hillside will be the horizontal equivalent which may be significantly less than the actual surface area.
