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[Malcolm Williamson]

> 
> We scanned some aerial photos at different scales,like 100%,120%,150%.
> We know the scale at which the aerial photographs were taken. Is there
> any provision in GRASS to directly get the resolution of each pixel.
> Actually what does the d.measure do. what it represents, I mean which scale, 
> how can we incorporate those, with the actual scale at which the
> photos were taken and the scanned scale.
>        In a crude way we can do like this. We know the #of rows & cols    
> and the scale. we can findout actual measure on the ground since we
> know the scale. If we divede the total measure(rowwise & col wise) by
> the #of rows and #of cols, I think we will get each pixel resolution.
> I'm i in right direction.
> All suggestions and ideas are appreciated, thanks
> srinivas challa
> 99chall2 at lab.cc.wmich.edu
> 

srinivas,
Your scanned photos should have been imported to a non-georeferenced x,y
GRASS location. Using known points on the photos, such as roads, and other
geographically-referenced GRASS data layers (digitized off of a map, perhaps),
you can then use i.group, i.target, i.points, and i.rectify (or i.rectify2) to
rectify and georeference your photos to a GRASS Location which _has_ a 
projection behind it. Then your d.measure, as well as r.report, r.stats, etc.,
will reflect the proper units.

Good luck!
-- 
Malcolm D. Williamson - Research Assistant       E-mail: malcolm at cast.uark.edu
Center for Advanced Spatial Technologies      Telephone: (501) 575-6159
Ozark Rm. 12                                        Fax: (501) 575-3846 
University of Arkansas              
Fayetteville, AR 72701