[GRASSLIST:2368] Re: v.proj help

[Glynn Clements]

Christian G. Tveen wrote:

> Then I've tried to project the data to mercator projection, into a new 
> handmade location. Here I cant display the projected data ! The 
> projection was done by inserting the following PROJ_INFO into the new 
> location/PERMANENT:
> 
> name: Mercator
> proj: merc
> ellps: clark66
> lat_0: 57.0
> lon_0:11.0
> zone: -1

lat_0 isn't a valid parameter for that projection.

> To get the WIND and DEFAULT_WIND files, I did a g.region on the imported 
> file and changed the projection to 99
> The WIND file looks like:
> 
> proj: 99
> zone:0
> north: 57:54:28N
> south: 54:24:11N
> east:    15:33:24E
> west: 7:38:57E
> cols: 99
> rows: 44
> e-w resol: 0:04:47.54
> n-s resol: 0:04:46.75

This isn't valid. The region boundaries and resolution have to be
specified in the map's coordinate system (i.e. feet/metres, not
degrees).

> I think the
> THen v.proj -s input=ponet location=global mapset=dk
> 
> The output is somewhat big numbers:
> north: 7911408
> south: 7211788
> east 502391
> west 364972

If I project your lat/lon region into the location:

	name: Mercator
	proj: merc
	ellps: clark66
	lat_ts: 0.0000000000
	lon_0: 11.0000000000
	k_0: 1.0000000000

I end up with:

	north:      7904761.9047619
	south:      7206349.20634921
	west:       -369444.44444444
	east:       504166.66666667

Which isn't that far off, except for the Western boundary. Maybe
something doesn't like the negative coordinate; most map projections
choose their parameters so that coordinates are always positive (e.g.
by adding a false Easting or Northing).

-- 
Glynn Clements <glynn.clements at virgin.net>