[GIS] How to convert ArcGIS points into Lat and Long

arcgis-desktop

I have no experience with GIS data but I have been tasked with taking an export from an ArcGIS database and converting the values into Lat and Long. The client we are helping also has very limited experience with the ArcGIS data they have so it is the blind asking the blind to help them.

Here is a sample of what the client has provided from their ArcGIS database.

1074409.65305250,14531615.53041425,North Garage
1074416.77442934,14531614.91000867,North Garage

What are the values they provided and is it possible to convert these values into Lat/Long?

Best Answer

Those records are giving you the X and Y (Easting and Northing) coordinates of two points. What you need to figure out is what coordinate system those numbers are using. Lat/long is one coordinate system, probably the best-known one, but there are hundreds of others available. Those look like they're in UTM. Normally the person giving you the data would have a better idea about what the coordinate system is, but it sounds like that's not the case here, so you need to do some detective work.

Normally you can figure this out, as long as you know where one or two of these points should be located in the real world and as long as the data isn't in some obscure coordinate system. It's hard to be 100% sure though, coordinate systems can be modified and you may think you have the right coordinate system only to find out later that the person who created the data changed it slightly and some of your data is in the wrong place. That isn't all that common though.

ETA: I assumed you had access to ArcGIS because of the ArcGIS tag, but reading the question again I don't think you do. If you don't, see Chaz's comment. If you do, try this:

  1. Open Arcmap, add a basemap (Streets, whatever), and navigate to where your points are supposed to be. The more specific you can be, the better, for example your list mentions a North Garage. If you know the building they're talking about and can find it on a map, do that (or if you can do it for any of the other features in the list).

  2. Go to the Data Frame Properties, Coordinate System tab, and pick a UTM coordinate system appropriate to your location in the world. If you're in North America, I'd start with UTM NAD83, Meters. Click OK.

  3. In the data frame, hover the mouse over the North Garage (or whatever feature you're using). The XY location shows up in the lower-right corner of ArcMap. Compare those numbers to the ones in your table. The order may be reversed from what's in your list, usually coordinates are listed with the X first, then Y, but that's not a rule. ArcMap shows them as X,Y. If the coordinates shown in ArcMap match your data in the same location, you've probably found a match and you now know with some certainty what coordinate system your data is in.

  4. Repeat steps 2 and 3, trying a different coordinate system each time, until you find one that shows the same coordinates as what's in your list for your known location.

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