I am currently preparing raster layers in QGIS to be fed into MaxEnt to run a species distribution model.

I downloaded climatic variables in ascii format from I downloaded from Adaptwest (https://adaptwest.databasin.org/pages/adaptwest-climatena) with the following parameters:

Projection    LAMBERT
Datum         WGS84
Spheroid      WGS84
Units         METERS
Zunits        NO
Xshift        0.0
Yshift        0.0

49  0  0.0 /* 1st standard parallel
77  0  0.0 /* 2nd standard parallel
-95  0  0.0 /* central meridian
0  0  0.0 /* latitude of projection's origin
0.0 /* false easting (meters)
0.0 /* false northing (meters)

I will need to crop this raster with states boundaries shape files in CSR WSG 84 but I am unable to successfully re-project the ASCII files so that they overlap with the states shape files.

I tried a solution posted in this Q&A site in which I created a CSR using the above parameters:

+proj=lcc +lat_1=49 +lat_2=77 +lat_0= 0 +lon_0=-95 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs

but I am still unable to re-project. I get no error messages but the outcome is wrong.

Any idea what am I doing wrong?

  • Does your asc file have a prj file or aux file with the projection defined? Are you trying to crop using gdal_warp with -cutline? If not how are you trying to crop your raster.. details are important here. – Michael Stimson May 14 '18 at 4:16
  • Try +proj=lcc +lat_1=49.00 +lat_2=77.00 +lat_0=0 +lon_0=-95 +x_0=0 +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs as your Proj.4 string... What spatial reference are you trying to convert to? – Michael Stimson May 14 '18 at 4:33
  • Hello Michael! Thanks for your response. I think there was a glitch in QGIS because I am now able to overlay my states shape files with the rasters by setting up the CSR to the one I created. However, when re-projecting: Raster>Projection>Warp to WGS 84 pseudo mercator, the raster values changed. Trying to figure out this part out now, but I guess I will need to post a different question for this. – Nayeli Carvajal May 14 '18 at 4:40
  • Are you trying to warp and clip at the same time? Try warping to EPSG:3857 (epsg.io/3857) first, transform your boundaries too from (I assume) EPSG:4326 (WGS84 Geographic) then warp to the same using cutline.. it might be having difficulty transforming the raster and the cutline at the same time. – Michael Stimson May 14 '18 at 4:53
  • I am trying to warp the layers first to make sure I am getting the same original values as this could really changed the outcome of my model. I read that the differences maybe due to the re-sampling method selected. I am unfortunately getting different values for each of the re-sampling methods, nothing near to the original values. – Nayeli Carvajal May 14 '18 at 5:05

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