State Plane Coordinate System (SPCS) Converter

Convert between US State Plane Coordinates (NAD83 Easting / Northing in US Survey Feet, International Feet, or Meters) and NAD83 / WGS84 Geographic Coordinates with Proj4js precision.

How the State Plane Coordinate System Limits Distortion to 1:10,000

The SPCS maintains a maximum scale distortion of 0.01% (1 part in 10,000) across zone widths by selecting projection geometry matched to each state's geographic orientation:

Lambert Conformal Conic (LCC) For States with East-West Extent Standard Parallel 1 (k = 1.0000) Standard Parallel 2 (k = 1.0000) Grid Scale Compressed (k < 1.0) Examples: Texas, Colorado, PA, Ohio Transverse Mercator (TM) For States with North-South Extent Central Meridian k < 1.0000 (e.g. 0.9999) Secant Lines (k = 1.0000) Examples: Illinois, Georgia, FL East/West

Real-World SPCS Geodetic Benchmarks

Surveyors and engineers cross-reference localized CAD drawings with global GNSS observations using verified benchmark coordinates:

Location / Landmark SPCS Zone & EPSG Easting (X, ftUS) Northing (Y, ftUS) WGS84 Geographic (Lat, Lon)
Texas State Capitol (Austin) TX Central (EPSG:2277) 3,113,854.21 10,072,410.85 30.274722°, -97.740556°
Los Angeles City Hall CA Zone 5 (EPSG:2229) 6,485,320.15 1,842,109.40 34.053720°, -118.242710°
Empire State Building (NYC) NY Long Island (EPSG:2263) 988,095.40 212,504.80 40.748440°, -73.985660°
Seattle Space Needle WA North (EPSG:2285) 1,267,420.50 229,810.15 47.620510°, -122.349280°

Authoritative US Geodetic Sources

  • NOAA National Geodetic Survey (NGS): NOAA Manual NOS NGS 5, State Plane Coordinate System of 1983, James E. Stem (1989).
  • National Institute of Standards and Technology (NIST): Deprecation of the United States Survey Foot, Federal Register Notice (85 FR 62698, Oct 5, 2020).
  • International Association of Oil & Gas Producers (IOGP): EPSG Geodetic Parameter Dataset v10.0+ for SPCS projection parameters.

Related US Geomatics Tools

US Survey Feet vs Int. Feet → The 2 ppm gap that causes 4-foot shifts in State Plane coordinates. UTM vs. State Plane Accuracy → Compare UTM 6° zone scale distortion against localized SPCS 1:10,000 ellipsoid scale limits. WGS84 vs. NAD83 Difference → Understand tectonic plate motion and 1.0–1.5 meter datum shifts. Grid to Ground Scale Factor → Compute combined elevation and grid distortion factors.