[GRASSLIST:5743] Re: mercator coordinates

[Glynn Clements]

grass grass wrote:

> > We are brand new grass users and we would like some advice on how to open a
> > mercator map in grass (if it is not a UTM) with longitude and latitude
> > coordinates instead of this weird easting and northing stuff that seems to
> > come up when you use d.where.

It can't be done.

GRASS uses linear coordinates but, for the Mercator projection,
degrees of latitude get further apart the further you get from the
equator (y is proportional to log(tan(latitude))).

AFAIK, the only projection for which projected coordinates have a
linear relationship to lat-lon coordinates is Equidistant Cylindrical
(Plate Carée).

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