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?
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It's a bit out of date, but the basic elements are there: find matching points between your image and a reference map (I'd now recommend http://getlatlon.com in favor the one at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
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!– speshAug 3, 2010 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".– speshAug 5, 2010 at 14:44
I do know of two web-based solutions that might be worth taking a look at:
- Map Rectifier from MetaCarta
- MapWarper created by Tim Waters
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.
you should be able to add more links now :) Oct 14, 2010 at 20:37
1Interestingly, I was just looking at MapWarper again the other day. The source is on GitHub: github.com/timwaters/mapwarper– mvexelNov 11, 2010 at 10:16
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.
You can also use the Image rectifier plug-in in MapWindow. It uses an enhanced 4 or 6 point algorithm.
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.pdf
The GRASS orthorectification workflow is available here: grassbook.org -> Left menu -> Sample chapter: -> Aerial + Ortho (PDF)– markusNDec 2, 2010 at 0:27
If you have or can create a *.geom file for your image, you can use orthoigen is gdal to quorthorectify your imagery.
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.
and is built with GDAL