State plane zone lookup
Finds SPCS83 zones by state or zone name, or the zones whose area of use covers a point, with each zone's NGS code, EPSG code, projection, and feet unit.
Found 3 zones.
| NGS code | Zone | EPSG | Projection | Feet unit |
|---|---|---|---|---|
| 0501 | Colorado North | 26953 | Lambert conformal conic | US survey feet |
| 0502 | Colorado Central | 26954 | Lambert conformal conic | US survey feet |
| 0503 | Colorado South | 26955 | Lambert conformal conic | US survey feet |
- Note
Provenance
- Computed by
- geodesy.spcs.zone-lookup 1.0.1, core 0.1.0
- Model
- Name match against the SPCS83 zone table, or the EPSG area-of-use box of each zone
- Accuracy
- Point lookup uses each zone's bounding box, so near a zone line more than one zone can match: confirm with the county list for the zone.
- Notes
- None
- Cites
- Stem, J. E., National Geodetic Survey, State Plane Coordinate System of 1983, NOAA Manual NOS NGS 5
Something look off?
How we got thisFormula, worked example, sources, and proof
Model: Name match against the SPCS83 zone table, or the EPSG area-of-use box of each zone
Accuracy: Point lookup uses each zone's bounding box, so near a zone line more than one zone can match: confirm with the county list for the zone.
When to use this: Use this to find the State Plane zone you need before projecting anything: by state, by the zone's own name, or by a point. Each zone comes back with its NGS code, its EPSG code, which projection it uses and which foot its foot-based twin is defined in.
Limitations: A point lookup uses each zone's published rectangular area of use, not the state boundary, so a point near a zone line matches both zones and a point just outside a state can still match its zone. Treat the answer as a shortlist and confirm against the county list for the zone. The zones are the SPCS83 ones; the older SPCS27 zones are different ground with different parameters and are not here. And the two feet matter: the same zone exists in metres and in feet, and the US survey foot and the international foot differ by two parts per million.
Worked example: Zones in Colorado. Source: NOAA Manual NOS NGS 5: Colorado North (0501), Central (0502), and South (0503). It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.
You enter
- State or zone
- Colorado
You get
- Count
- 3
- Note
- Zones whose name matches every word.
Review: Not yet independently reviewed by a geodesist.
Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.
Status: version 1.0.1, core 0.1.0. See this tool in the verification report.
Changes
- 2026-09-23, fixed: Identifiers no longer show digit grouping: the EPSG code in SPCS83 forward and zone lookup reads 32129, not 32,129, and the decimal year in magnetic declination reads 2026.71, not 2,026.71 (all version 1.0.1). SPCS83 forward in US survey feet also gave the deprecated-unit warning (LEGACY_UNIT) twice, once for easting and once for northing; every tool now gives it once per result. Values are unchanged. Changelog
Checked against: 30 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.
Sources
- State Plane Coordinate System of 1983, NOAA Manual NOS NGS 5, Stem, J. E., National Geodetic Survey, NOAA Manual NOS NGS 5 (reprinted with corrections). Zone constants (Appendix) and the Lambert and transverse Mercator mapping equations.
Learn the concept: Grid vs ground distance explained, State plane coordinates explained