[GRASS-user] Rectify error / maximum number of GCPs?

Benjamin Deschamps bdesc100 at gmail.com
Fri Mar 20 20:21:19 EDT 2009

I am trying to georectify RADARSAT-2 imagery in GRASS 6.4.0RC3 (Mac OS 10.5).
The imagery is accompanied by 350 GCPs. When using the GUI georectify tool I
get the following error when I click on the "start georectifying" button:

can't read "xy(51)": no such element in array
can't read "xy(51)": no such element in array
    while executing
"$xy($gcpnum) insert     0 "[lindex $fields 0] [lindex $fields 1]""
    (procedure "GRMap::get_gcp" line 34)
    invoked from within
    (procedure "GRMap::gcpwin" line 119)
    invoked from within
    (procedure "GRMap::refmap" line 33)
    invoked from within
    ("uplevel" body line 1)
    invoked from within
"uplevel \#0 $cmd"
    (procedure "Button::_release" line 18)
    invoked from within
"Button::_release .grstart.mf.frame.start.a"
    (command bound to event)

Is there a limit of 50 GCPs?

If I click to ignore the error, it loads the GCP table with the 50 first
points. When I click the button to georectify, GRASS freezes, and nothing is
added to the wgs84 location. If I edit the POINTS file manually and remove
the blank line below the 50th point, I don't get the error message.

My steps have been:

1) create a location in wgs84 lat/long coordinates
2) import the dataset to a new location using r.in.gdal, indicating to use
wgs84 location for GCP projection
3) re-open grass in the wgs84 location and open georectify menu
4) Select the other mapset where data was imported (PERMANENT shows up in
the box)
5) Select the group from that mapset
6) Select on the maps form that group
7) Click "start georeferencing"

Thanks, Benjamin
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