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I'm looking for an open source tool/workflow (even a command line one) to obtain what it is advertised in programs like

http://www.inpho.de/index.php?seite=index_orthovista

http://www.orthomapper.com/color_balance_example.html

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009t000001v8000000

I already tested OSSIM and GRASS, for instance

http://trac.osgeo.org/ossim/wiki/histogram_operations

http://grass.osgeo.org/grass64/manuals/i.image.mosaic.html

but results are not as expected. I also had no luck with

http://www.lizardtech.com/products/geoexpress/

that is the only close source that I was able to test thanks to a trial.

Maybe it depends from my input data, so a small working sample dataset would be highly appreciated.

By the way, does Orfeo do something like that?

Thanks in advance

PS I'm open to use even a non GIS software

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2 Answers 2

I would recommend using the open source GIS Whitebox GAT (http://www.uoguelph.ca/~hydrogeo/Whitebox/) for creating seamless mosaics from aerial photography. Please note that John Lindsay is the lead developer of Whitebox GAT (according to his bio).

Here's a possible workflow:

  1. If you have multiple colour air photos, split them into their RGB components using the Split Colour Composite tool. You will want to mosaic each band separately then create a colour composite mosaic at the end.

  2. You may want to use the Correct Vignetting tool (to be released in version 3.0.6) to remove the gradual darkening towards the image corners that commonly occurs with air photos. This will greatly improve the mosaic quality.

  3. Use the 'Find Tie Points' tool (to be released in version 3.0.6) to automatically find tie points between adjacent images in the group of images. Notice that you don't have to do this for each RGB band, but rather only use one (e.g. the red band images).

  4. Use the Image Rectification tool to register adjacent images.

  5. Use the Mosaic With Feathering tool to join adjacent images. This may have to be done several times as you build up the images, and you'll have to do it for each of the Red, Green and Blue bands. Importantly, this tool will join the images such that the boundaries between them are not obvious in any way. There will be gradual gradients from one image to the next and it will also perform histogram matching to match the radiometric properties of each image in the mosaic.

  6. Create a colour composite mosaic by using the Create Colour Composite tool, combining the Red, Green, and Blue mosaics together.

  7. If the colour quality is not as good as you would like, I'd recommend using the Balance Colour Enhancement tool to improve it. This works quite well.

I don't have a colour air photo example, but here is a seamless greyscale mosaic from air photos using this workflow. Notice that it has the vector footprints of the original three air photos:

enter image description here

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From the Help Center: You must disclose your affiliation in your answers. –  user3461 Oct 7 '13 at 16:16
    
@GeoKevin Apologies, you can perhaps see why I was confused over this point given the number of QGIS devs on this site that answer questions without disclosing their affiliation. I suppose that GIS.se is the defacto QGIS forum though, isn't it? –  user21951 Oct 7 '13 at 18:33
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@GeoKevin He has a point there. Also in this post his answer is like a how-to, which imo are more than welcome here especially if it's from an OS tool? –  nickves Oct 7 '13 at 18:46
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@nickves, Thank you for your support. GeoKevin's comment was particularly irritating in light of the fact that the OP was not looking for a software-specific solution but was simply looking for an OS solution. Some commenters on GIS.se act like I am stepping on toes by recommending an alternative. It's open-minded individuals like yourself that I spend countless hours developing open source software for. Certain GIS.se frequenters however make me feel like I never want to code another line! –  user21951 Oct 7 '13 at 19:16
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It is a real stretch to conceive of such a detailed and well-documented reply as being "spam." –  whuber Oct 8 '13 at 16:46
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There is a GRASS GIS 7 Addon, i.histo.match which performs histogram matching on the given input images. The histogram matching method is based on the method Cumulative Distribution Function (CDF) of two or more histograms. For RGB images you will mosaic them color by color. If needed, a post-mosaic color optimization can be achieved with i.landsat.rgb (it also works for other RGB data).

See http://grasswiki.osgeo.org/wiki/AddOns/GRASS_7/imagery#i.histo.match

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