Q75 - Indicates if arc is a boundary for a 7.5 minute quad. Q100BASE - Defines 30x60 min. Q250BASE - Defines 1 x 2 degree quadrangle boundaries for cartographic use. These boundaries differ significantly from the typical rectangular quadrangle shape. This data set was created to serve as base map information.
Data are appropriate for use at a regional scale and are intended as a reference.
Data are not appropriate as a geodetic or engineering base. Tics were generated as well, one at each quad corner. Latitude and longitude values were assigned to the arcs in the generation process. Two arcs for irregularly shaped 15' quadrangles in the Chicago area were added. The data were projected to Lambert Conformal Conic.