I have followed this great tutorial on pan sharpening using Grass GIS 7 (I'm using beta 3). Everything in the tutorial seemed to have worked, but my final output is not as expected (pictured below). PanSharp RGB output

I tried with various sharpening methods, colour balancing stages and with and without atmospheric correction. I also tried with different images.

Any advice on where I'm going wrong?

Here's the output from r.univar:

Of the non-null cells:

n: 41623319 minimum: 0.089549 maximum: 1.17079 range: 1.08124 mean: 0.161591 mean of absolute values: 0.161591 standard deviation: 0.110987 variance: 0.0123181 variation coefficient: 68.6836 % sum: 6725971.35730981

  • What are the pixel value stats? Please add the output of r.univar somechannel to your post.
    – markusN
    Aug 27 '14 at 20:17
  • Is it possible that a radiance versus reflectance mishap happened?
    – markusN
    Aug 30 '14 at 21:47
  • Radiance-reflectance mishap - I'm not sure. Would it Provide some insight if I ran i.toar in verbose mode?
    – Simon
    Aug 31 '14 at 15:28
  • Please, post full commands to make clear, for example, on which maps the statistics refer to. Also, for the sharpening part, you can give a try of this one: i.fusion.hpf (works for GRASS GIS ver. 7.x). Dec 8 '14 at 19:30

Thank you Nikos and Markus for the comments.

Using Nikos' hpf module I get a nice pansharpened image. The steps taken to do this (also in i.fusion.hpf documentation):

  • Download the module from github, open Grass 7.x.x
  • In the Grass command console (bottom of the layer manager window, second tab from the left), navigate to the directory where you extracted the github archive (eg: cd c:\somefolder\ifusion...). Then run 'make MODULE_TOPDIR=$GISBASE'
  • Run the i.fusion.hpf module (eg. i.fusion.hpf -l -c --o pan=L_B8 msx=L_B2,L_B3,L_B4 center=high modulation=max). Refer to documentation for explanations and other options. For me, it took 21 mins
  • Colour enhance (eg. i.colors.enhance red=L_B4.hpf@Morogoro green=L_B3.hpf@Morogoro blue=L_B2.hpf@Morogoro)
  • display rgb or make a composite (eg. r.composite red=L_B4.hpf@Morogoro green=L_B3.hpf@Morogoro blue=L_B2.hpf@Morogoro output=MorogoroPanSharpen

(This was done on a Windows machine)

Here's the result from an image of part of Tanzania - before (left) and after (right): Pansharpened before and after

The river and crops are sharper and you can make out clumps of trees on the barren patches.

  • The sharpening effect is obvious in the screenshots (more details on the right image). Yet, the colors are not vivid/contrast not high(?). Maybe the appearance can be improved further by experimenting with i.colors.enhance. What is the purpose of the sharpening in this case? Nice visuals or subsequent classification? Apr 1 '15 at 1:08

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