Subject: i.rectify never finishes processing with null data in region
Platform: GNU/Linux/i386
grass obtained from: Mirror of Trento site
grass binary for platform: Compiled from Sources
GRASS Version: 5.0.2
I was using a USGS DRG on a 7.5 Quad.
I had another map that would be a small part of that.
I was going to rectify the map and overlay it on the topo.
I found that I needed to make null the parts of the small map that were blank
so that I could overlay the topo map and not lose data by overwriting with blanks.
I was able to rectify the file and then remove the blank areas while using rectified
destination location. This rectification would take about 1 1/2 hours.
This was not quite right so I decided to change the blank raster data to nulls
before rectification. When I then rectified the file, the job never finished.
After about 24 hours I cancelled the job. I was only using 3 GCPs and was doing
a linear transformation (1 dim). I only had one geo-referenced coordinate, but
I had the scale and the north south direction on the scanned map which I used
to calculate 2 more GCPs. As I write this I wonder what would happen if one
of my GCPs, was made null. Would it mess up the rectification? |
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