# Identifying Projected Coordinate System based on coordinates

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06-12-2014 10:39 AM
New Contributor III
Hello,

I have a set of coordinates. All I know about them is that they are for locations in the US in the NAD 83 State Plane Coordinate System. Is there any way to narrow down which of the many state plane coordinate systems they might belong to short of going through each one?

Here's an example:
X: 12121117
Y: 3478079

Tags (2)
Esri Notable Contributor
Hello,

I have a set of coordinates. All I know about them is that they are for locations in the US in the NAD 83 State Plane Coordinate System. Is there any way to narrow down which of the many state plane coordinate systems they might belong to short of going through each one?

Here's an example:
X: 12121117
Y: 3478079

No idea where it is? Ugh. Luckily, the values are rather large.

So here's how I'm doing it. Check the false easting and false northing values for the NAD83 state plane zones. A nice summary is in John P. Snyder's Map Projections: A Working Manual, USGS Professional Paper 1395 (pages 373-376), which is online. Those will give you a general idea of the coordinate values for the zone. The largest in meters is Michigan North with 8 million. I'm almost positive that Michigan isn't wide enough to have eastings of 12 million. (check by adding state or county boundary data to ArcMap and setting the data frame to the Michigan North zone)

Therefore, these values must be in international or US survey feet.

So the equivalent coordinates in meters are (assuming US survey feet):

X: 3694523.85 m
Y: 1060120.6 m

There are no transverse Mercator zones which have a large enough false easting value. In the Lambert conic zones, Virginia South looks like the one.

If you're looking for a general solution, there just isn't one. There are too many zones that have similar values (if the coordinates are smaller) so you won't be able to differentiate unless you have other information. As an example, all California zones have the same false easting and northing values.

Melita