[R-sig-Geo] Raster projection alignment issues

[Wall, Wade A ERDC-RDE-CERL-IL]

Hi all,

I posted this over at gis.stackexchange.com, but thought this user group may be interested.

I downloaded  raster data from  http://gdo-dcp.ucllnl.org/downscaled_cmip_projections/dcpInterface.html#Welcomein

The BCSD-CMIP5 data is found under the tab "Projections: Complete Archives".
The files are in netCDF format, but am running into some issues. The original raster data (let's call it rast1) when imported has the extent

xmin 235.25
xmax 293
ymin 25.125
ymax 52.875

and a crs of +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0

The other objects (both sp and raster) I am working with contain negative values for xmin and xmax


xmin        : -122.8021

xmax        : -75.38249

ymin        : 31.78881

ymax        : 47.15952



When I attempt to reproject the raster data into Albers Equal Area (+proj=aea +lat_1=20 +lat_2=60 +lat_0=40 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83

+units=m +no_defs +ellps=GRS80+towgs84=0,0,0)using the following code:



rast_new = projectRaster(rast1, rast2) ## rast2 is a raster with the crs for Albers Equal Area



the extents still don't line up, so I have to do the following.



rast_new = projectExtent(rast1,rast2)

rast_new = projectRaster(rast1,rast_new)

values(rast_new) = values(rast1) ### This is necessary because all the values were NA



However, rast_new, even though its crs is defined as Albers Equal Area, does not project correctly. Even when I export these files from R and open in ArcGIS, the issues persist. However, if I import the netCDF files directly into ArcGIS and reproject, there are no problems.



Any clues as to what I am doing wrong?



Thanks for any assistance.


Wade A. Wall
US Army ERDC-CERL
P.O. Box 9005
Champaign, IL  61826-9005
1-217-373-4420
Wade.A.Wall at usace.army.mil




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