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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

PolyGeo
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CovenStine
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    This sounds like one of our most frequently asked coordinate system questions: http://gis.stackexchange.com/questions/7839/identifying-coordinate-system-of-shapefile-when-unknown – PolyGeo Sep 19 '14 at 06:10
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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 '14 at 06:29
  • Have you tried the USA_Contiguos CRS definitions by ESRI (EPSG:102003 to 102005)? – AndreJ Sep 19 '14 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 '14 at 16:08
  • Sorry about duplicate
    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.
    Extents
    In layer spatial reference system units
    xMin,yMin -2340812.00,314764.50 : xMax,yMax 2158476.25,3051828.50
    Layer Spatial Reference System
    +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
    Thanks for your help!     – CovenStine Sep 23 '14 at 03:06
  • apparently editing with multi-line text is not a happy situation... I'm sorry for the multiple posts and the fact that it's yet another FAQ-esque question. Normally I'd never ask such a noob question, I've just tried all the duh-answers (or so I imagine) and am still coming up blank. Thanks for your help, I really appreciate it. – CovenStine Sep 23 '14 at 03:12

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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

fluidmotion
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