[GRASS-user] GRASS63cvs v.rast.stats reports zero for many CATs

[Brandon M. Gabler]

Fellow GRASSers -

I am using GRASS 6.3 cvs, the Kynge's build, and I have an issue  
using v.rast.stats on a raster of slope. Many (n>100) of my  
archaeological sites, which are all polygons, produced 9 columns of  
zeros for the slope stat calculations. I repeated the exercise, using  
different column names, and it repeated the results.

The oddest part is that I successfully calculated elevation stats  
from a DEM raster using the same v.rast.stats command. The slope  
raster was produced directly from the DEM, so resolution, etc. are  
exactly the same.

I investigated some of the polys that were missing slope information,  
and indeed, the raster is completely intact in the area of these  
polygons, with values other than zero, and the polygon itself is clean.

In attempting to do the same calculations with my aspect raster,  
there were also many sites where the aspect calculation resulted in 0  
(for both of these, even the 'n' field, number of cells, is 0). These  
sites were not always the same as the ones that had slope  
calculations of zeros!

I am running the stat calculations with slope again, after cleaning  
the vector file, but I still am not optimistic that this will help  
since my v.rast.stats calculations on elevation were successful where  
the slope ones were not.

Also, it takes about 7 hours to calculate the stats for my 893  
polygons (16 meter grid resolution probably has something to do with  
it, but wanted to make sure this isn't a fixable thing).

I tried searching the user list, but found nothing related to this  
problem with v.rast.stats.
Thanks all,
Brandon
_______________________
Brandon M. Gabler
Doctoral Candidate
Department of Anthropology
University of Arizona
Tucson, AZ 85721
Phone: (520) 621-8455
Fax: (520) 621-2088
bgabler at email.arizona.edu

"Who? When? Whither? are the questions with which the archaeologist  
challenges the refuse heaps, scattered potsherds, and broken shafts,  
to tell of the builders who came and lived and went their way into  
the templed past." -- Edgar Lee Hewett, in Pajarito Plateau and its  
Ancient People, 1938


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