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I'm trying to figure out the coordinate system of some data I downloaded from a no-longer-maintained USDA website.

The data's still accurate, it's just floating in space.

I've tried several state-plane systems, a number of UTM systems, etc. My brute force method is running out of steam.

I'm using Quantum GIS, so what I've done is started a new project, imported the state of new mexico's counties to the system and let the metadata assign its coordinate system (EPSG:4269 - NAD83).

I then enabled on-the-fly reprojection, set the project's coordinate system to "NAD83 / UTM zone 13N," and imported my un-defined coordinate data.

I tried about 30 different coordinate systems so far, and none of them get the data any closer than almost-in-line east-to-west and out of line by about 1000 miles north-to-south.

The image below is a screenshot of qGIS with Erodability due to wind data, with an assigned system (EPSG:26915 - NAD83 / UTM zone 13N) based on a guess, which is obviously wrong.

I've marked the origin with a small dot, if it helps.

For what it's worth, I went over the metadata files, and I didn't see anything relating to coordinates.

qGIS NM counties, C values, zero

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  • 1
    This sounds like one of our most frequently asked coordinate system questions: gis.stackexchange.com/questions/7839/…
    – PolyGeo ♦
    Sep 19, 2014 at 6:10
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    You should show us the metadata, it's not coordinates you are after but a "coordinate reference system", like a PROJ.4 or WKT string.
    – mdsumner
    Sep 19, 2014 at 6:29
  • Have you tried the USA_Contiguos CRS definitions by ESRI (EPSG:102003 to 102005)?
    – AndreJ
    Sep 19, 2014 at 11:11
  • Could you post the extents at least? Even without positions that are easily aligned with a reference layer, we should be able to figure out the units, and where the lat of origin is approximately.
    – mkennedy
    Sep 19, 2014 at 16:08
  • Sorry about duplicate<br/>well, I tried all of the ESRI coordinate systems, and they all put the data up in canada (I put in the rhode island shoreline for reference, and it was WELL above that). As far as metadata, everyhing's blank except the properties and extents. Left out properties for char limit.<br/> Extents<br/> In layer spatial reference system units<br/> xMin,yMin -2340812.00,314764.50 : xMax,yMax 2158476.25,3051828.50<br/> Layer Spatial Reference System<br/> +proj=eqdc +lat_0=39 +lon_0=-96 +lat_1=33 +lat_2=45 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs<br/> Thanks for your help!
    – CovenStine
    Sep 23, 2014 at 3:06

1 Answer 1

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as @AndreJoost mentioned, it could be one of the lambert projections - you could probably rule out any UTM or state plane options because the dataset covers the continental U.S. It could also be a modified version of EPSG:102003 which i did not have in my QGIS list - a USGS version. to test this one, i added a custom CRS as '+ proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23.0 +lon_0=-96 +x_0=0 +y+0=0 +datum=NAD83 +units=m +no_defs

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  • searching by the EPSG #'s Qgis 2.4 has all of the esri systems built in, they're just not labelled as such, just a generic USA_CONTIGUOUS_[descriptor]_CONIC
    – CovenStine
    Sep 23, 2014 at 3:14
  • oops, duh - thanks. is the url for these data available?
    – fluidmotion
    Sep 27, 2014 at 9:36

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