Hi, I have a problem with converting the WFDEI data set i use (meta information can be found here: http://www.eu-watch.org/gfx_content/documents/README-WFDEI.pdf[/url]) to the correct projected coordinate system in meter format (I need it in USA_Contiguous_Albers_Equal_Area_Conic_USGS; geographic coordinate system GCS_North_American_1983)
The WFDEi data comes in lat long (degrees) in a .nc format but i am not able to convert it to my desired projected coordinate system, since the projection is listed as unknown in arcgis and since i could not find any information about it in the meta data.
I got these informations from the .nc file but I dont really know how to interprete them:
the readMe says: All WFDEI data files include grid-box centre longitude and latitude (on a regular longitude-latitude 720 x 360 grid).
"a regular longitude-latitude .. grid" is likely a geographic lat/long grid; on what datum... who knows? try a sphere.
the "Generated grid information" reinforces that impression: gridtype = lonlat The 'gridsize = 6477' squares with the xsize = 127 and ysize = 51 xinc = 0.5 and yinc = 0.5, so the cells are half degree
The center of the lower left cell is xfirst = -125.37598, yfirst = 24.562113 (remember the "..data files include grid-box CENTRE longitude and latitude.." from the readme)
so, subtract 2.5 from the given x and y to find the lower left corner.
That is all pretty simple; the datum may be a problem (self-identified scientists types tend to ignore such things) give it a shot defining the datum as wgs84 or GCS_North_American_1983 and see how it lines up once you have it projected to your target.
If it is off, try defining the grid on a sphere (size is, again, anyone's guess) if you do that, you may have to create a custom (dummy) transformation with all the values at 0 to get from the sphere to the NA83 spheroid.
if it is still off a consistant distance, you can build in a coordinate shift.
This may sound like it can be a little snakey (a lot snakey), but people that build these types of files often don't pay much attention to mapping conventions; they just want things to be consistant within their own user community....
I managed to get the data close to my desired projection but however what kind of false easting I apply, I cannot align it. I attached you a screenshot on how it looks like now.. can u give me a guess on what number I have to enter? Thank you a lot!