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Does anyone have a recommendation for a work flow for georeferencing high resolution aerial photography using open source tools? Comparison of user friendliness and robustness between Quantum GIS versus GDAL?

Thank you!

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7 Answers

up vote 16 down vote accepted

GDAL user-friendliness is basically nonexistent, but hot damn does it ever work well. I wrote up this guide to my own georeferencing experiments a few years ago: http://mike.teczno.com/notes/flea-market-mapping.html

It's a bit out of date, but the basic elements are there: find matching points between your image and a reference map (I'd now recommend http://getlatlon.com in favor the one at http://gorissen.info), use gdal_translate to knock up a virtual raster, and then you're basically done in the sense that the resulting VRT file can be converted to the GeoTIFF or tile of your choice.

I'm doing a lot with this right now, including collaborating with Tim Waters on the excellent server-side Map Warper mentioned in this thread, so there may be some new stuff in the near future loosely based on some experiments I did in JS last year: http://mike.teczno.com/notes/canvas-warp.html

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Michal, very cool thanks! I was curious of how to find the pixel location and you mention that you used Photoshop's info palette, which is helpful. I think I can get away with using a 1st order transformation. Thanks for all the info! –  spesh Aug 3 '10 at 15:40
    
QGIS 1.5 has just been released and looking through the changelog (qgis.org/en/component/content/article/108.html) I noticed that "Inclusion of GDAL Raster tools plugin into QGIS core". –  spesh Aug 5 '10 at 14:44
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I do know of two web-based solutions that might be worth taking a look at:

I'm pretty sure Tim Waters open sourced his code, so even if these particular tools don't suit your needs, looking at their source might give you some insights.

Sorry, I can't post more than one external link because I am apparently less than reputable.

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you should be able to add more links now :) –  matt wilkie Oct 14 '10 at 20:37
    
Interestingly, I was just looking at MapWarper again the other day. The source is on GitHub: github.com/timwaters/mapwarper –  mvexel Nov 11 '10 at 10:16
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I find QGis's georeferencer to be pretty decent for a point and click tool. I wrote a little guide - image georeferencing with QGIS - which is slightly Canadian data-source specific, but walks through all the steps you need to get an arbitrary map into QGis.

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Since you are using aerial images: do you need orthorectification? In that case I guess ILWIS would be your best bet, although GRASS also supports it (I haven't tried that myself though).

Work flow for ILWIS is described here: http://spatial-analyst.net/PDF/TN_Ortofoto_in_ILWIS.pd

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The GRASS orthorectification workflow is available here: grassbook.org -> Left menu -> Sample chapter: -> Aerial + Ortho (PDF) –  markusN Dec 2 '10 at 0:27
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You can also use the Image rectifier plug-in in MapWindow. It uses an enhanced 4 or 6 point algorithm.

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If you have or can create a *.geom file for your image, you can use orthoigen is gdal to quorthorectify your imagery.

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OpenEV comes with FWTools, seems OK to me but I load 300 MB images into QGIS easily and deal with them there. So I can recommend it only from casual use.

http://OpenEV.sourceforge.net

Includes NITF

and is built with GDAL

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