Glynn Clements <glynn.clements@virgin.net> schrieb am 22.01.04 04:44:16:
Jason Horn wrote:
> Only
> problem is, my data are lat-lon, so that's not so easy since polar
> coordinates do not measure units of distance.
That shouldn't matter. Most of GRASS doesn't care whether the units
are metres, feet, degrees, micro-fathoms or whatever; they're just
units.
>
Unlikely. d.rast (etc) positions and scales the image such that:
c) the scale factor is the same for both dimensions.
Does this include somthing like lon_display := lon_map / cos(lat) to get at least approximately correct aspect ratio?
Wolfgang
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Wolfgang von Hansen wrote:
> > Only
> > problem is, my data are lat-lon, so that's not so easy since polar
> > coordinates do not measure units of distance.
>
> That shouldn't matter. Most of GRASS doesn't care whether the units
> are metres, feet, degrees, micro-fathoms or whatever; they're just
> units.
> >
> Unlikely. d.rast (etc) positions and scales the image such that:
>
> c) the scale factor is the same for both dimensions.
Does this include somthing like lon_display := lon_map / cos(lat) to
get at least approximately correct aspect ratio?
No. Regardless of the coordinate system, the transformation is just
uniform scaling plus offset. E.g. for a lat-lon location, one degree
of latitude and one degree of longitude will appear the same size on
screen, regardless of the latitude.
--
Glynn Clements <glynn.clements@virgin.net>