1. A method for trimming geographic data that defines polygons to boundaries of a quadrangle, comprising: converting the geographic data into map coordinates in an azimuthal map projection, each map coordinate describing a projected point having an azimuthal angle proportional to longitude of the point, and having a radius from the center of the azimuthal map projection proportional to both longitude and latitude of the point; trimming one or more polygons along a lower longitude limit of the quadrangle in the azimuthal map projection; trimming one or more polygons along an upper longitude limit of the quadrangle in the azimuthal map projection; and converting the map coordinates in the azimuthal map projection back to geographic data.