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I'm wanting to create a data layer using some open crime data from Salt Lake City, but I can't figure out the coordinate system they are using. See the link below to view the data. (You'll have to scroll to the far right to see the X and Y coordinates.)

https://opendata.utah.gov/Public-Safety/SALT-LAKE-CITY-POLICE-CASES-2016/trgz-4r9d

I'm new to GIS.

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    What software are you using ? – Sethinacan Apr 14 '16 at 6:49
  • I'm using QGIS for this. – Carl Hancock Apr 15 '16 at 18:52
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From the Discus tab of the page:

x y points are state plane coordinates 

Since Salt Lake City is in Utah, take all CRS that are valid for that state, and compare the location against an OpenStreetmap or other basemap.

You will get lucky with EPSG:32043 NAD27 / Utah Central:

enter image description here

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  • Just to clarify, if we assume that Discus comment is accurate (a reasonable starting place), then we know it is a state plane coordinate system. That gives us the options of NAD 1927 or NAD 1983, then Utah North, Utah Central, or Utah South (given that we know it's Utah data). You can take a first stab at that if you have an idea where in Utah it's likely to be, then you've narrowed down the trial and error that gets you to the final answer. You also have to figure out if it's in meters or feet, the data will be scrunched or expanded if you guess wrong. – karl Apr 14 '16 at 15:15
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    I tried NAD83 too, but the points end up in Texas then. NAD27 has a different false Easting and Northing to avoid errors. BTW the URL states that the data is from Utah. stateplane.ret3.net notes that Utah central is correct for Salt Lake City. – AndreJ Apr 14 '16 at 15:21
  • Yup. Just wanted to clarify the steps a bit for more general application. You do seem to have found it. – karl Apr 14 '16 at 15:27
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When you want to make a new layer from an attribute table, the coordinate system of the data should be mentioned in the meta data.
And if it's not, you should find it through trial and error.
For example here it is clear that the data has a projected coordinate system and it is belonged to Salt Lake city, so provide another layer of the city which has a defined coordinate system and then start and create your new layer using the popular projected coordinate systems that are used in US and the new layer to the .mxd map to see in which case, the layer is shown just right up in its place

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From what I see on the website (at least on a mobile device) this data cannot be downloaded in a native GIS format (like shapefile). If it could, such a format generally comes with various metadata, including projection info. Anyway, if you don't plan to combine it with data from other sources it doesn't matter what projection your GIS software thinks it is. Just pick any Projected coordonate system (the X/Y tells us it's a projected system, a geographical one would have coordinates of the type: Lat/Long).

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