Hi,
Using v.rast.stats in grass6.3 both in cygwin and native windows,
v.rast.stats vector=myupland_lowland@allah_valley layer=1
raster=allah_dem@allah_valley colprefix=dem percentile=90
I get this error
:/GRASS/scripts/v.rast.stats: r.cats: command not found
I see no entry in the 6.3 manual on r.cats
any ideas on using v.rast.stats?
On Wed, May 21, 2008 at 2:44 AM, Jonathan Greenberg
<greenberg@ucdavis.edu> wrote:
Juan:
Some responses below:
Well, that's exactly the problem, i cannot make a complete mosaic for the
region i'm working on with only images taken on one day, and it adds
another
problem: the images do not overlay well... if they did, i would been able
to
do a radiometric normalization easily (as Johnattan Greenberg
suggested)...By "do not overlay well" I assume you mean they aren't well orthorectified
to one another -- although I consider this a "must do" for mosaicking and
for any level of image-to-image work (because of the time savings), you
COULD manually pick PIFs in the overlap zone (e.g. you'd pick a point in the
reference image, then visually pick the corresponding pixel in the
uncorrected image) -- orthorectifying first saves you the time of having to
pick two points per image -- rather, you just pick one point. How many
images do you have in your mosaic? Image-to-image rectification with
landsat imagery is fairly painless, shouldn't take you much more than 30
mins per image once you get going with it.
At any rate, once you pick your PIFs, you can use v.what.rast or starspan
(starspan.casil.ucdavis.edu) to get this data out to a table to do the
regression calculations.So my problem now is how to overlay landsat images taken in different
days.
I've already asked for help on this issue (with no solution so far; mail
subject="mosaic with landsat geotiff"), so guess i'll resume that
thread...if it is simply an "automatic contrast" adjustment, you could linearly
interpolate between bands so they matched. (but then which is correct?) I
don't think it would be though, as LANDSAT has fixed calibration for each
band.How's that?
This is what I suggested as well -- the question of which one is "correct"
is somewhat moot -- your goal, as I understand it, is to have all of the
images in the same radiometric scale, so you can just pick one (usually one
that's in the middle of your mosaic, and often temporally at the "edge" of
your time period (either a very early or a very recent image). Ifif you run i.landsat.rgb on the two images with the same parameters do
they
match up well?what do you mean with 'the same parameters'? (maybe "cropping
intensity"...)that doesn't touch the values, only the colors, but it may
give you a clue about the cause of the difference.How exactly? as an example, i can see a subtle difference in the color of
water in a river as it pases on to another 'tile', but what does it means,
i
don't have a clue... (the values changes from: |32|40|86| to |20|26|69|,
for
bands 3, 2, 1 respectively)I guess the important thing is the ratio of the bands, not the exact
values
of one particular band. I take it you see a hard line at the boundary in
the processed image?i suspect you mean the same as Johnattan G. with the radiometric
normalization... anyway, i don't know what you mean with 'proccesed
image'.
The original images come with a null region as a result of the
georreferencing, and after i use r.null -r to remove the NULL-value bitmap
file, yes, there is a hard line in the boundary, but what would that mean?It just means your images aren't radiometrically normalized to one another.
If you correctly normalize them you won't see a line in the mosaic.Hamish
JM
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Jonathan A. Greenberg, PhD
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Center for Spatial Technologies and Remote Sensing (CSTARS)
University of California, Davis
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