[GRASSLIST:5494] Re: NVIZ and GTOPO30 on osx

[Ian Macmillan]

Quoting Glynn Clements <glynn.clements at virgin.net>:

> NVIZ doesn't like lat-lon locations; it acts as if the horizontal
> units are metres. So, for a GTOPO30 DEM, you have a 40m x 50m region,
> with 4000m high peaks (100 times the width of the region).
> 
> Importing into an X-Y or Plate Carée (Equidistant Cylindrical)
> location should produce more sensible results.
> 
> -- 
> Glynn Clements <glynn.clements at virgin.net>
> 
> 

Thanks for the tips, while these projections are a little better, they are still a little distorted.  XY reads the file as 6000 rows by 4800 columns, and consequently ~4000 units high, however a row is not 1 meter across.  Roughly the same problem with eqc.  Turns out the best thing is to bring in the gtopo30 from a lat-long location into a UTM location using r.proj.  Then use nviz from the UTM location.  You just need to be sure that the region you are interested in with the gtopo30 tile is in the UTM zone of the current location in order to avoid distortion.  Thinking about projections was definitely the trick.  Thanks.

-ian