Joyce Anne Nagle
nagle at hanover-crrel.army.mil
Mon Mar 8 09:13:37 EST 1993
I have several questions:
1. When we are using i.points and we say yes for the digitizer we get
ERROR - Could not lock digitizer.
Check for existance of /usr/gis/locks .
Contact your GRASS system administrator
I am the "GRASS system administrator" and what I have checked is whether
the digitizer is working. I checked it using v.digit and it works fine. We have
a Calcomp 9500 and there is a driver for it that works fine with v.digit.
Any ideas of what to try next?
2. I am doing a rectification of a Landsat TM image using the i.group, i.target,
i.points, and i.rectify sequence. When using i.points the image looses alot of its
resolution when I zoom in - it looks like there is pixel replication going on. So
I tried resetting the window using g.region and then looked at the image using
d.rast and the same thing is there. How can I display the ground control point regions
in 1:1 resolution using i.points so that I can pick out my ground control points?
3. Can you rectifiy all 7 Landsat TM bands at once or do I have to do this for each
band? Can I put all 7 bands into a group and then do this all at once?
4. Why is the rms error so large when I am using 6 or 7 ground control points? It is
about 8 pixels where you would expect 1-2 pixel rms error. I think this is directly
related to the problem I am having in question 2.
Joyce A. Nagle
U.S. Army Cold Regions Research and Engineering Laboratory (CRREL)
Remote Sensing and GIS Center email: nagle at hanover-crrel.army.mil
72 Lyme Road phone: (603) 646-4161 / 4100
Hanover, NH 03755-1290 fax: (603) 646-4278
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