Projections request...

[Allan Hollander]

It's not that complicated.  As Eric notes, the proj.4 library supports
false eastings and northing, and it's just a matter of getting the right
parameters in the PROJ_INFO file.  (At least this is the case in GRASS 5. 
I don't know about GRASS 4).

This is the projection file (the PROJ_INFO file in the 
directory calif/PERMANENT) I use for the California Teale Albers
projection.

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

Best wishes,  

Allan (another California GRASS user)


On Mon, 14 Aug 2000, Morten Hulden wrote:

> 
> Hi Eric,
> 
> you can add support for false easting&northing for Alber's Equal Area in
> GRASS5beta by editing the file src/libes/gis/geo_init.c. On line 35, just
> after the last TABLE[AEA] definition, add the following lines:
> 
> 	TABLE[AEA][X0].ask = 1;
> 	TABLE[AEA][X0].def_exists = 1;
> 	TABLE[AEA][X0].deflt = 0.0;
> 
> 	TABLE[AEA][Y0].ask = 1;
> 	TABLE[AEA][Y0].def_exists = 1;
> 	TABLE[AEA][Y0].deflt = 0.0;
> 
> Then recompile.
> 
> regards
> Morten Hulden
> 
> 
> On Sun, 13 Aug 2000, Eric G . Miller wrote:
> 
> > Several months ago, I asked about False Northing/Eastings for the Albers
> > Equal Area Projection.  GRASS currently doesn't allow the specification
> > of these items for this projection.  Recently I was contacted by another
> > person who read my previous posting about this subject -- wondering if I
> > had a solution.
> > 
> > Anyway, a number of state agencies in California have standardised on an
> > Albers Equal Area Projection that has a false northing.  There is quite
> > a bit of data available in this projection.  Unfortunately, there's no
> > clean way to get this data into GRASS at the moment.  I know the proj4
> > library supports this feature; so, I'm wondering if it would be possible
> > to implement it?  I've been searching through the GRASS code base, but
> > am not familiar enough with it to know how all the projection code ties
> > together.  I know there are many other things on the TODO list, but
> > perhaps someone familiar with the projection code could point me in the
> > right direction(s)?
> > 
> > Thanks.
> > 
>