[Proj] hammer parameters?

Hamish hamish_b at yahoo.com
Wed Jan 12 18:01:10 EST 2011

William wrote:
> But, GDAL rejects ob_tran, so I can't really do anything
> useful with it.  I can't use GRASS to project a raster
> because hammer appears to not have an inverse (I saw a patch
> posted to the list last December, but code didn't appear to
> correctly match the formulas on the mentioned page),

to get around that limitation of r.proj in GRASS, either 

- r.to.vect (skip topology), then v.proj

- or..
the no topology thing can be problematic, so what I did recently
for reprojecting the ETOPO1 dataset to Winkel Tripel (see [1])
was output to a text file with r.out.xyz, then in the destination
location import that with cs2cs | r.in.xyz.

[1] http://adhoc.osgeo.osuosl.org/grass/alternate_projections/earthquakes_wintri.png

> and I don't know if GRASS supports ob_tran either.

AFAIK grass supports anything proj4 does, plus some more.
If GDAL rejects something the chances are that GRASS might as
well, but perhaps not. proj4 support is the much more important

fwiw, the line in $GISBASE/etc/proj-params.table reads:

HAMMER:Hammer & Eckert-Greifendorff:LAT0=ask,0.0;LON0=ask,20.0;MSFACT=ask,1.0;WFACT=ask,0.5

(value after the "ask" is the default answer)



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