aerial photo mosaic

[Joe Leone]

Hi, 
I have been trying to create a mosaic from aerial photo.  I have managed to get 
the photos into GRASS and rectified them using the imagery commands. (Thanks to 
help from the list!) 

When I use d.rast -o "filename" for each of the images they display correctly ( 
In the correct geographic position with some overlap).

Now I am trying to create one GRASS raster file using r.patch.
If I use the command "r.patch input=009,007,005 output=patched",
005 displays correctly. ie I can see roads, and other features. However, 009 and 
007 are in the coorect positions but the pixels are jumbled -  I can not 
distinguish features.

Things I have tried.
 run r.support on 009 007 etc
 
 r.resample before r.patch using the default region
  
 specified both the default region and the minimum regions in i.rectify2
 r.mapcalc  "newmap= if(009,009,007)" - In this case none of the features are 
recognisable.
 
 
 It is something to do with the fact that some photos are "darker" than others?
 
 
 Any suggestion ?
 Thanks 
 Joe


Joe Leone
Western Australian Laboratory
CSIRO Wildlife & Ecology
LMB 4, PO MIDLAND WESTERN AUSTRALIA 6056
Phone +61 8 9290 8108
Fax   +61 8 9290 8134
Email  Joe.Leone at per.dwe.csiro.au