[GRASS-user] Re: xy to lat long

[Marcello Gorini]

Raphael wrote:
>> > i have imported the etopo dem (geotifff) into grass.
>> > It appears to be in XY and i would like to convert
>> > these to lat longs.

Markus:
>> But in any case the ETOPO2 will be better (see wiki for an
>> article how to import it).

Hamish:
>yes for ease of import, but not so much for modernity. 
>"Historic ETOPO2v2 and ETOPO5 global relief grids are deprecated
>but still available."


Another option is to go for the GEBCO_08 or SRTM30_plus grid. I use to
download a gebco grid directly in lat long from
https://www.bodc.ac.uk/data/online_delivery/gebco/select/ in netCDF format.

Then I literally "go by the book" and do what the GRASS book tell us. I
import the grid into a latlong location using r.in.gdal and generates a
vector of the bounding region:
r.in.gdal -o input=gebco_input.nc output=gebco_output
g.region rast=gebco_output
v.in.region output=boundingbox

Then I open a projected location, project the bounding box and then the
grid:
v.proj input=boundingbox location=GEBCO_GEODETIC mapset=MYMAPSET --o
g.region vect=boundingbox res=1000 -pa
r.proj in=gebco_output location=GEBCO_GEODETIC mapset=MYMAPSET method=cubic
--o

Of course this is the opposite direction of what you want, but if you go for
the gebco grid, it is already in latlong anyway. But then you can use this
procedure to project back and forth your grid.

Hope it helps,
Marcello.




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