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I am completely new to QGIS (and mapping in general), and I can't get my layers to line up.

QGIS Version: 3.2.1-Bonn Standalone-installer Windows 10 64-bit

All of my layers are in the USA Contiguous Albers Equal Area projection. Currently, I have three layers:

  • Site Coordinates
  • World Imagery layer from ESRI
  • Cropland Data Layer (CDL) from USDA-NASS CropScape

My coordinates line up perfectly with the World Imagery layer. However, the CDL is floating somewhere out in the universe and won't line up.

CDL Extent:
48885.0000000000000000,2818725.0000000000000000 :
117585.0000000000000000,2930685.0000000000000000

I downloaded the CDL as a zipped file containing a .tif and a .vat.dbf.tif file. I unzipped the file and uploaded it to QGIS as a .tif file.

Is it possible that the georeferencing for the .tif file is encoded in the .vat.dbf.tif file? How do I import the Cropland Data Layer to QGIS?

Kadir Şahbaz
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Emily Wine
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2 Answers2

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According to the FAQ for CropScape and Cropland Data Layers:

What projections are used?

The CDL is processed using the Albers Equal-Area Conic USGS Projection (USA_Contiguous_Albers_Equal_Area_Conic_USGS_version) with a spheroid of GRS 1980 and datum of NAD83. The downloadable zip files from the SARS website and CropScape are offered in the native Albers projection.

In order to conform to Geospatial Data Gateway technical specifications, any CDL data downloaded through the Geospatial Data Gateway is re-projected from Albers to the dominant Universal Transverse Mercator (UTM) zone with a spheroid and datum of WGS84. The one exception to the UTM projection is for Wisconsin. Wisconsin is projected using the Wisconsin Transverse Mercator (WTM) projection. This WTM projection is based on the 1991 adjustment to NAD83, and is called WTM83/91. Projection parameters and additional information about WTM83/91 is posted on the DNR website: http://dnr.wi.gov/maps/gis/wtm8391.html

If you downloaded the CDL layer from the Geospatial Data Gateway, it's in the "dominant" (I assume this means local) UTM zone with a spheroid and datum of WGS84.

If you downloaded the CDL layer from the SARS website or CropScape, it's in USA_Contiguous_Albers_Equal_Area_Conic_USGS_version (not USA Contiguous Albers Equal Area Conic). This seems to be a non-standard projection, because it doesn't have an EPSG code, and QGIS doesn't have it. You can create a custom projection, using the proj4 definition:

+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs

I found the proj4 definition on github, so no promises that it's correct. All credit goes to patchdynamics.

It might be easier to download the layer from Geospatial Data Gateway instead.

Community
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csk
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I seem to have found a solution. CropScape claims to provide data in EPSG:102003, however on inspection the data is actually EPSG:5070.

QGIS 3 on windows read it as 102003 for some reason. Changing that in the properties puts the file in the correct place. Hopefully this issue is resolved.

Emily Wine
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