[GRASSLIST:2939] Re: s.to.rast help

Kevin Slover kjslover at nhc.noaa.gov
Fri Jan 18 09:08:19 EST 2002

thanks for the response.  I guess it is difficult to explain...You
answer has given me a bit more insight on the s.to.rast command. 
However, with that explanation, it makes it that much more puzzling. 
Taking your example below, the 0 representing my data point, and the X's
representing the "buffered" cells...my data point "cell" is given a NULL
value, and the other "buffered" cells are given a value.  I will attach
a tif image, which might give more of an explanation of the problem.  I
am sure the outputted white areas on the raster are null, as I have done
both r.what.rast and r.out.xyz, and get NULL values.  I am sure there is
some simple solution to this problem, that I am overlooking some step
somewhere, but it is evading me right now.  
And, as I said in the last email, r.fillnulls doesn't recognize the NULL
values, yet they are clearly there...any ideas??

> I'm sorry, but it's not clear what the problem is.  The s.to.rast module
> creates a cell value for each site it falls within (given the current
> region settings).  If you ask for additional cells, the cells grow out
> in every direction by the number given.  So, "buffered" by three cells
> gives you something the following (for a given site):
>        X X X X X X X
>        X X X X X X X
>        X X X X X X X
>        X X X O X X X
>        X X X X X X X
>        X X X X X X X
>        X X X X X X X
> So, if your sites are 500m apart, with 100m cell size, the edges of the
> "buffered" cells will probably colide (and you should get warnings about
> this).
> As far as nulls go, are you sure there any remaining?  At the beginning
> of the run, the program writes out all cells as NULL.  It then writes
> the corresponding sites data cells (as buffered), possibly clobbering
> previously written values (aforementioned warning).
> --
> Eric G. Miller <egm2 at jps.net>

        LTJG Kevin Slover,NOAA   GIS
              Tropical Prediction Center/National Hurricane Center
                    11691 SW 17th Street Miami FL 33165
                 Work: (305) 229-4456 Fax : (305) 553-1264
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