# How to identify unknown coordinate type and convert to lat/lon?

I have some coordinates from an old Oracle database (AMANDA) and I don't recognize the format.

For example, converting these coordinates: 3109020, 10114224 Should result in a point near latitude, longitude: 30.195855, -97.756467

Does anyone recognize this format and how to convert to lat/lon?

• Please post the lat/long (and datum) of "a location" so that people can test their guess. Apr 19, 2019 at 18:43
• The only information I have is that these coordinates (3109020, 10114224) should point to 2103 LEMON DRIVE, AUSTIN, Texas, 78744, USA. Apr 19, 2019 at 19:05
– csk
Apr 19, 2019 at 19:43
• Sure seems like there should be a web site/service where you can enter x,y long/lat, push a button, then be presented with a list of possible coordinate systems. Apr 19, 2019 at 19:55
• @KirkKuykendall There is an online tool called Projfinder that works well with registered coordinate systems and takes your x, y as input, and a map display to reference the location. I gave it a try in this specific case, but it did not find a match unfortunately. Apr 20, 2019 at 22:21

That looks like a projected Coordinate System, with units in either feet or meters.

You can figure out what coordinate system your points are in by trying out different coordinate conversions on this website.

Enter the lat/long of a coordinate, choose the target CRS, and click convert. Try out different target CRS's until the conversion gives you the known coordinates.

Given the location, start by testing CRS's with Texas in their name, eg:

• EPSG 3082, NAD83 / Texas Centric Lambert Conformal
• EPSG 3081, NAD83 / Texas State Mapping System
• etc

It shouldn't take long to test all 10 Texas-specific CRS's. If none of them work, expand the search to US-specific CRS's, and North American-specific CRS's.

Remember that the US often uses US survey feet or (international) feet for the unit of measure. When you see large numbers like that, check the foot-based coordinate reference systems first. Austin falls into the Texas Central zone in the State Plane Coordinate System, maybe try that one first. You will find it difficult to determine which geographic CRS is being used. It's probably one of the NAD 83 ones, but there have been several re-adjustments and coordinate differ at the centimeter to decimeter-level.

An alternate approach is to figure out where the origin of the CRS is. Then you can limit your search to CRS's with that origin. Find the origin by measuring from the known point, 3109020 units to the west and 10114224 to the south. Since the data is in the US, you'll have to test it with both meters and feet. If the origin is on the equator you're probably looking at a UTM projection.

• I tried all of the Texas conversions and US conversions that seemed relevant. No luck as of yet. I'll try second method and report back. Apr 20, 2019 at 20:16
• I had another hypothesis - what if these coordinates are supposed to have decimal places in them? The lat/long point at (31.09020N, 101.14224W) is in Texas. It's a couple of hundred miles WNW of where the corresponding point is supposed to be, though.
– csk
Apr 21, 2019 at 1:18