WGS 84 vs NAD 83: why it matters
Phones and Google Maps use WGS 84. Survey gear on a US RTK network uses NAD 83(2011). The same spot on the ground gets different numbers in each, about 3 to 5 feet apart across the lower 48 today. (We checked six cities with NGS's published transformation, EPSG:8970, at late 2026.)
If you pick "Phone or Google Maps" above, we shift your point into NAD 83 with that same NGS transformation. It is good to a few inches, not survey-grade. For legal or survey work, use NGS Coordinate Conversion and Transformation Tool (NCAT) or NGS's HTDP.
How we checked the math
This page uses proj4js with the official EPSG definitions for every NAD 83 State Plane zone, in meters, US survey feet and international feet. We compared it with NGS NCAT at 12 points in 12 zones (PA South, OH North, TX Central, TX North Central, CA 3, CA 6, AZ Central, MI South, OR North, SC, FL East and AK 1). Every result matched NCAT within 0.003 ft.
Which unit should I use?
Use the unit your state's law names for SPCS 83. We pick it for you. 40 states use the US survey foot, 6 use the international foot, and a few have no foot law, so their official numbers are in meters. Mixing up the two feet can move a point several feet. See the unit converter.
Source: NOAA Special Publication NOS NGS 13, The State Plane Coordinate System (2018), Appendix C, Table C1.
UTM in one minute
UTM splits the world into 60 north-south strips, each 6° of longitude wide. The lower 48 sit in zones 10 to 19. UTM is always in meters. We use NAD 83 UTM (EPSG 26901 to 26923).
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