[GRASS-user] unexpected i.pansharpen results
nik at nikosalexandris.net
Wed Jul 31 08:47:37 PDT 2013
Nikos Alexandris wrote:
> >>> I can't get any decent looking colors, with any of the methods. I
> >>> wonder if my images are not properly "aligned" or the like.
Moritz Lennert wrote:
> Getting back to this just for clarification. What do you call "decent
> looking colors" ?
apply to my sentence "s/decent looking colors/usable images"
> Have you looked at the example images in the man page ?
>  http://grass.osgeo.org/grass70/manuals/i.pansharpen.html
> They show quite different colors depending on the technique used.
This is not the problem that I have. Nor is it the one Haziq described in the
Q&A at <http://gis.stackexchange.com/q/39174/5256>.
> Are you trying to get them all to look like the top left ("natural
> color") image ?
No. I simply try to get usable output from 11-bit bands fed in i.pansharpen.
The only usable output, no matter the method actually, is when rescaling the
input bands to 8-bit. Tested with my working data (IKONOS, QuickBird) as well as with some
publicly available IKONOS data.
I am delivering 18 examples in which none of them appears ok to me. I guess I don't know
how to use the module. Will post images in trac, if possible, else in my wiki user-page.
I don't provide any 8-bit examples. All of my attempts, so far, with 8-bit images work fine --
they look from acceptable to really good depending on some re-balancing, be it manually
playing with color-tables or using i.landsat.rgb
Nevertheless, I 'd like to see only one example using a >8-bit set of bands in which
i.pansharpen works as expected. Then I know for sure that, once again I have messed-up a
normal runnig process :-). I am a Great specialist doing this... :D
So, here it goes.
# 1) We have publicly available IKONOS images:
Get for example the first one:
# 2) Import in GRASS' db, convert from DN to Radiance to Reflectance. Details
in the Wiki:
# 3) Let's have a look at the "input" ranges:
# 11-bit DNs, ranging in...
# Reflectances -- note to self: fix r.support below!
title=echo Blue band (Top of Atmosphere Reflectance) (Blue_ToAR)
title=echo Green band (Top of Atmosphere Reflectance) (Green_ToAR)
title=echo NIR band (Top of Atmosphere Reflectance) (NIR_ToAR)
title=echo Pan band (Top of Atmosphere Reflectance) (Pan_ToAR)
title=echo Red band (Top of Atmosphere Reflectance) (Red_ToAR)
# 4) i.pansharpen -- all of them, three methods -- from my history
18 31.Jul.13 [ 15:54:36 ] i.pansharpen sharpen=brovey pan=Pan_Radiance
ms1=Blue_Radiance ms2=Green_Radiance ms3=Red_Radiance
19 31.Jul.13 [ 15:54:46 ] i.pansharpen sharpen=brovey pan=Pan_ToAR
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