Atlas Sheet to Lat/Long Coordinate Converter

New Jersey Geological Survey (NJGS) atlas sheets partition the state into a grid of 7.5-minute USGS topographic quadrangles. Each sheet maps to a precise bounding box defined by corner coordinates in decimal degrees. Field workers, environmental consultants, and permit applicants routinely reference these sheet numbers, yet a single transposition error when converting to latitude/longitude can mislocate a site by kilometers. This tool performs exact bidirectional conversion between atlas sheet identifiers, decimal degrees (°), and degrees-minutes-seconds (DMS) notation. It covers all 200+ quadrangles tiling New Jersey from sheet 1 (High Point) to sheet 230 (Cape May Point).

The underlying grid follows USGS 7.5′ series conventions: each sheet spans 7.5′ of longitude and 7.5′ of latitude. Conversion from DMS to decimal uses the identity DD = D + M60 + S3600. Note: this tool assumes NAD83 datum alignment consistent with current NJGS publications. Coordinates falling outside New Jersey’s bounding box (38.9°N - 41.4°N, 73.9°W - 75.6°W) will not resolve to a valid sheet.

Conversion between Degrees-Minutes-Seconds and decimal degrees uses the following identity:

Where DD = decimal degrees, D = whole degrees, M = arc-minutes (0 - 59), and S = arc-seconds (0 - 59.999).

The inverse conversion extracts components:

Atlas sheet identification uses a containment test. A coordinate (lat, lon) falls within sheet n if:

Where the subscripts denote the southwest and northeast corner coordinates of the sheet bounding box. Each USGS 7.5′ quadrangle spans 0.125° in both latitude and longitude.