[GRASSLIST:9485] Re: SRTM shifted 0.5 the res in X and Y axis from the r.mapcalc output

[William Kyngesburye]

Ack, I was partially right about the zoom thing.  d.zoom restrains  
itself to the region resolution, but it's aligning to a whole degree,  
not the 1.5 sec offset that it started at.  Thus it appears to be  
half a cell off.

On Dec 14, 2005, at 2:50 PM, William Kyngesburye wrote:

> I don't think there is a problem.  I worried about and checked this  
> when I started converting and filling SRTM data.
>
> Since the cell centers of a SRTM tile range from degree to the next  
> degree (so there is a 1 cell overlap between all tiles), the GRASS  
> region will appear to be off by 1.5 seconds - it won't line up on  
> even degrees.
>
> The problem, in your example at least may be that you used d.zoom  
> before r.mapcalc.  d.zoom doesn't restrain itself to cell  
> boundaries (as you can see from the region after zooming), and  
> r.mapcalc will create the test raster at whatever region is set.   
> Then, of course they will not align.
>

-----
William Kyngesburye <kyngchaos at kyngchaos.com>
http://www.kyngchaos.com/

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