[GRASS-user] v.in.ascii with large files

[Hamish]

Seb wrote:
> 
> Thanks.  Using etopo2 was exactly what I needed.

looks good! tried it with NVIZ yet?

> It seems some problem occurred when reprojecting the raster from the
> geographic location to my Albers equal area projection location,
> because values for lat 70 or thereabouts are missing
> (http://members.shaw.ca/sluque/earctic.png).  These values are
> definitely there in the original geographic location.

Are you 100% sure? test with:
  g.region rast=bathy_map
  r.univar bathy_map
and check the NULL cell count.


> Maybe I'm still not setting an appropriate projection:
> 
> 
> -PROJ_INFO-------------------------------------------------
> name       : Albers Equal Area
> datum      : wgs84
> towgs84    : 0.000,0.000,0.000
> proj       : aea
> ellps      : wgs84
> a          : 6378137.0000000000
> es         : 0.0066943800
> f          : 298.2572235630
> lat_0      : 65.0000000000
> lat_1      : 70.0000000000
> lat_2      : 75.0000000000
> lon_0      : -130.0000000000
> x_0        : 0.0000000000
> y_0        : 0.0000000000
> -PROJ_UNITS------------------------------------------------
> unit       : meter
> units      : meters
> meters     : 1.0


If the error is at 70N, and lat_1 = 70N, perhaps there is a bug there?
If so it would be a very rare one, as this code is very well tested and
AEA is a pretty common projection.


My gut guess is some sort of aliasing problem with r.in.xyz where the
g.region settings at import do not exactly match the original data's
grid resolution and some cells do not get any data. Try r.in.xyz with
method=n and check for cells with 0 or 2 data points in them around the
problematic 70N.


Hamish

ps- 'd.grid -g size=5' is nice.