[GRASSLIST:6297] Re: California Albers and false northing

[Ian MacMillan]

Tim, not sure if this helps, but here goes.  Whenever I use albers 
equal area for California, it needs to be in nad27, which has the clark 
1866 ellipsoid.  For nad83 stuff, I can't remember right now for sure, 
but I think it uses the grs80 ellipsoid.  Also, everyplace that I have 
seen landsat data, it comes in utm, but mebbe that is just me.  If it 
helps, the only difference btwn your proj_info file and mine is that 
mine specifies
datum: nad27

G'luck
-Ian

On Mar 30, 2005, at 2:30 PM, Tim De Chant wrote:

> I'm currently working on getting Landsat images for the Bay Area into 
> GRASS 6.1cvs (Mac OS X) but I keep running into issues with the 
> projection.  I've searched the list and came up with one solution, 
> which was to manually edit the PROJ_INFO file into this:
>
> name: Albers Equal Area
> proj: aea
> ellps: clark66
> a: 6378206.4000000004
> es: 0.0067686580
> lat_0: 0.0000000000
> lat_1: 34.0000000000
> lat_2: 40.5000000000
> lon_0: -120.0000000000
> y_0: -4000000
>
> This returns an error saying the dataset PROJ_INFO doesn't match.  
> Here's what the GeoTIFF contains:
>
> name: Albers Equal Area
> proj: aea
> datum: nad83
> a: 6378137
> es: 0.0066943800
> lat_1: 34
> lat_2: 40.5
> lat_0: 0
> lon_0: -120
> x_0: 0
> y_0: -4000000
> no_defs: defined
>
> I've tried modifying the PROJ_INFO file to match this to no avail.  
> I've also tried to override the projection information in the dataset 
> with no luck (under both variants of the PROJ_INFO file).
>
> Does anyone have any advice for working with California Albers?  I'm a 
> new user (so thanks for bearing with me).
>
> Tim
> __________________________________________
> Tim De Chant
>     University of California, Berkeley
>     Environmental Science, Policy, and Management
>     137 Mulford Hall #3114
>     Berkeley, CA 94720-3114
>     (510) 643-3910
>