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Joyce Anne Nagle nagle at
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.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
72 Lyme Road                         phone:  (603) 646-4161 / 4100
Hanover, NH  03755-1290              fax:    (603) 646-4278

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