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The latter map is much more easily compared with Hearne's original map than one drawn on the polyconic projection in common use at the present time.

Chart Projections The earth is projected, so to speak, upon a chart in three different ways - the Mercator Projection, the Polyconic Projection and the Gnomonic Projection.

The Polyconic Projection The theory of the Polyconic Projection is based upon conceiving the earth�s surface as a series of cones, each one having the parallel as its base and its vertex in the point where a tangent to the earth at that latitude intersects the earth�s axis.

The Polyconic Projection is especially adapted to surveying, but is also employed to some extent in charts of the U. S. Coast & Geodetic Survey.