ABSTRACT
In computer-assisted mapping, the computation of the coordinates of a point proceeds according to the following three cases. For the first, given the geographical coordinates (Bi ,li ) of points in the mapping area, we can calculate their plane rectangular coordinates (xi ,yi ) from map projection equations x = f 1(B, l),y =f 2(B, l). For the second, if the plane rectangular coordinates (xi yti on the original base map are known, we can obtain their geographical coordinates (5Bi ,li ) using the inverse formulae for the projection, and then obtain the values (x,i .yi of the newly edited map from its forward projection equations. For the third case, as in the second case, the plane rectangular coordinates (xji ,yi of the original base map are given. First, from formulae for map projection transformation, we can directly compute the plane rectangular coordinates (x,,i vyi on the corresponding newly edited map. All these cases belong to the problem of transformation of the coordinatessthe points. They can be summed up as three types according to nature of the research. The first type, (3,, Bi )li > ⇔, ii yi )he goal of map projection study, and the second type, i.e. (x,, y,i >i Yt )(Xi ,Yi s the aim of map projection transformation.
