The modified polyconic projection for the IMW

The modified Polyconic map projection designed by Lallemand and adopted for the International Map of the World between 1909 and 1962 has two meridians and two parallels which are true to scale. Constructed geometrically in the past, forward and inverse coordinate transformations may be calculated analytically in order to transfer data from existing quadrangles to other maps. The equations for these transformations are derived and used to calculate representative tables of coordinates andscale factors. Although the projection is neither equal-area nor conformai, scale does not vary more than 0.06% throughout the quadrangle.