Digital Geodata Series
DGS98-4 A 30-Second State Plane Coordinate Grid for New Jersey

Abstract

A 30-second grid covering New Jersey was generated using the ARC/INFO Geographic Information System (GIS). The grid was created and built as a tool for georegistering page size (8.5" x 11") field sheets using a GIS. The grid was generated as a geographic grid then projected to the 1983 North American Datum in State Plane Coordinate Feet. The grid was built solely as a line coverage and updated with line attributes indicating the value of each arc segment in degrees, minutes, and seconds (for example, 743000 equals 74 degrees, 30 minutes, and 00 seconds). A set of coordinate registration points (tics) covering New Jersey were generated at each latitudinal and longitudinal intersection point. Tic locations were compared to corresponding tics from the NJDEP 7-1/2' grid to check spatial accuracy. The comparison of 138 tic locations showed no spatial deviation between coverages to the nearest tenth of a foot.

 The 30-second coordinate interval provides a GIS basis for registering field sheets that use photoimagery near their maximum spatial resolution. About 64, 30-second tiles cover a quarterquad image (Figure 3). Figures 3, 4, and 5 shows the image resolution of a 30-second tile with respect to an orthoquarterquad image. Figure 4 shows that a 30-second tile fits on a 8.5" x 11" page at about the 1:10,000 scale. Figure 5 shows the quarterquad image near its maximum resolution at the 1:4000 scale (the NJDEP quarterquad images are reported to have a resolution of 5 feet to a pixel).