[GRASS-user] rectifying digital images
Hi, I have a lot of aerial photos I need rectify. The data came from an incomplete project intending to acquire geospatial data for landslide risk assessment. The project ended prematurely. Here are the details: Images were acquired using this method. Two GPS receivers were used, one attached to the laptop to facilitate the navigation of the airplane and the other to the camera to determine the geographic location of the center of the photographs. The plane flew along the flight lines indicated in the plan. The photographs were taken along the flight line using a professional Kodak N14 digital SLR camera, which has a resolution of 14 megapixels. The camera was fastened to a mount, made from plywood and customized to accommodate the camera and the laptop computer. The seat next to the pilot was detached to make room for the mount. A camera door, designed specially for this purpose, replaced the normal Cessna 172 passenger door. What do I have now: over 800 photos GPS point location for each photo Quickbird image of the whole study area According to their report: There is difficulty in mosaicking the photographs. The original plan was to stitch the photographs together to create a composite image. But the tilt in the photographs due to the movement of the aircraft requires that certain adjustments be made. Any ideas on how to resolve this. As far as I know, you need certain camera parameters to orthorectify aerial photos CAMERA NAME: camera name__ CAMERA IDENTIFICATION: identification___ CALIBRATED FOCAL LENGTH mm.:_ POINT OF SYMMETRY (X) mm.:_ POINT OF SYMMETRY (Y) mm.:_ MAXIMUM NUMBER OF FIDUCIALS:_ How do I get this? Is it OK to rectify the imges from the quickbird satellite data? cheers, maning ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
Hello Maning, Yes the actually important data concerns the camera properties. I fear your images won't be easy to handle : I guess your camera is not properly an aerial survey camera system, is it ? each image should show fiducial marks on its edges, and you should have a calibration certificate providing data such as focal length, fiducial marks position and so on. Let us know a bit more about the camera. Le samedi 05 janvier 2008 à 15:24 +0800, maning sambale a écrit : > Hi, > > I have a lot of aerial photos I need rectify. The data came from an > incomplete project intending to acquire geospatial data for landslide > risk assessment. > The project ended prematurely. > > Here are the details: > Images were acquired using this method. > > Two GPS receivers were used, one attached to the laptop to facilitate > the navigation of the > airplane and the other to the camera to determine the geographic location of > the > center of the photographs. The plane flew along the flight lines > indicated in the plan. > The photographs were taken along the flight line using a professional > Kodak N14 digital > SLR camera, which has a resolution of 14 megapixels. The camera was > fastened to a > mount, made from plywood and customized to accommodate the camera and the > laptop > computer. The seat next to the pilot was detached to make room for the mount. > A > camera door, designed specially for this purpose, replaced the normal Cessna > 172 > passenger door. > > What do I have now: > over 800 photos > GPS point location for each photo > Quickbird image of the whole study area > > According to their report: > There is difficulty in mosaicking the photographs. The > original plan was to stitch the photographs together to create a > composite image. > But the tilt in the photographs due to the movement of the aircraft > requires that > certain adjustments be made. > > Any ideas on how to resolve this. As far as I know, you need certain > camera parameters to orthorectify aerial photos > CAMERA NAME: camera name__ > CAMERA IDENTIFICATION: identification___ > CALIBRATED FOCAL LENGTH mm.:_ > POINT OF SYMMETRY (X) mm.:_ > POINT OF SYMMETRY (Y) mm.:_ > MAXIMUM NUMBER OF FIDUCIALS:_ > > > How do I get this? Is it OK to rectify the imges from the quickbird > satellite data? > > cheers, > > maning > ___ > grass-user mailing list > grass-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-user > ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
Hi Maning, if I understand you right, the purpose is to obtain a georeferenced mosaic of the aerial photographs. There are several ways to get to there. The easiest is to georeference each aerial photograph against your Quickbird imagery. This is straightforward and well documented in the GRASS help. Then you mosaic the photographs together, either with the GRASS script or, if you're not happy with the results of i.image.mosaic, use r.mapcalc and get inspiration from i.image.mosaic. This should already give you a fairly good result. if the camera was tilted against the ground which is apparently the case with your aerial photographs, steep slopes and large differences in elevation within an image might cause distortions which are not removed by simple georectification, unless you use a brute force approach with the orthorectified Quickbird imagery, i.e. at least 100 control points per image and the strongest rubbersheeting method available. Orthorectification is apparently only supported for analogue aerial photography in GRASS, because you need to know points of symmetry and the location of fiducial marks. Nowadays orthorectification of aerial photography taken with a digital camera requires you to know not more than the CCD resolution, focal length and flying height above ground, but this applies only to some commercial software packages. It helps to have a camera calibration data sheet, but you can get away without it. Anyway, digital cameras are apparently not supported in i.ortho.photo. I heard of some tools that can add fiducial marks to digital photographs, but don't know where to get them and how they work, and I would advise against patching like this. Not sure if that helps, but good luck, Markus maning sambale wrote: > Hi, > > I have a lot of aerial photos I need rectify. The data came from an > incomplete project intending to acquire geospatial data for landslide > risk assessment. > The project ended prematurely. > > Here are the details: > Images were acquired using this method. > > Two GPS receivers were used, one attached to the laptop to facilitate > the navigation of the > airplane and the other to the camera to determine the geographic location of > the > center of the photographs. The plane flew along the flight lines > indicated in the plan. > The photographs were taken along the flight line using a professional > Kodak N14 digital > SLR camera, which has a resolution of 14 megapixels. The camera was > fastened to a > mount, made from plywood and customized to accommodate the camera and the > laptop > computer. The seat next to the pilot was detached to make room for the mount. > A > camera door, designed specially for this purpose, replaced the normal Cessna > 172 > passenger door. > > What do I have now: > over 800 photos > GPS point location for each photo > Quickbird image of the whole study area > > According to their report: > There is difficulty in mosaicking the photographs. The > original plan was to stitch the photographs together to create a > composite image. > But the tilt in the photographs due to the movement of the aircraft > requires that > certain adjustments be made. > > Any ideas on how to resolve this. As far as I know, you need certain > camera parameters to orthorectify aerial photos > CAMERA NAME: camera name__ > CAMERA IDENTIFICATION: identification___ > CALIBRATED FOCAL LENGTH mm.:_ > POINT OF SYMMETRY (X) mm.:_ > POINT OF SYMMETRY (Y) mm.:_ > MAXIMUM NUMBER OF FIDUCIALS:_ > > > How do I get this? Is it OK to rectify the imges from the quickbird > satellite data? > > cheers, > > maning > ___ > grass-user mailing list > grass-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-user > > > ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
On Jan 5, 2008 8:24 AM, maning sambale <[EMAIL PROTECTED]> wrote: ... > The photographs were taken along the flight line using a professional > Kodak N14 digital SLR camera, which has a resolution of 14 megapixels. You can figure out camera parameters with 'jhead': http://www.sentex.net/~mwandel/jhead/ ... > What do I have now: > over 800 photos > GPS point location for each photo > Quickbird image of the whole study area > > According to their report: > There is difficulty in mosaicking the photographs. The > original plan was to stitch the photographs together to create a > composite image. Indeed, AFAIK you really need to do bundle block adjustment. The i.ortho.photo module is restriced to single frame rectification. I once received a script collection to use Octave and GRASS to perform bundle block adjustment but never got that working (still have the code, we could contact the author). Randomly seeking the internet, I found http://www.ics.forth.gr/~lourakis/sba/ sba: A Generic Sparse Bundle Adjustment C/C++ Package Based on the Levenberg-Marquardt Algorithm (GPL'ed) > But the tilt in the photographs due to the movement of the aircraft > requires that certain adjustments be made. Definitely. Markus -- Open Source Geospatial Foundation http://www.osgeo.org/ http://www.grassbook.org/ ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
On Jan 5, 2008 1:35 PM, Markus Metz <[EMAIL PROTECTED]> wrote: ... > Anyway, digital cameras are apparently not supported in i.ortho.photo. Why this? I did so, using a handheld digital camera: M. Neteler, D. Grasso, I. Michelazzi, L. Miori, S. Merler, and C. Furlanello, 2005. An integrated toolbox for image registration, fusion and classification. International Journal of Geoinformatics. Special Issue on FOSS/GRASS 2004 & GIS-IDEAS 2004, 1(1), pp. 51-61, March 2005. PDF: http://ojs.info.gscc.osaka-cu.ac.jp/IJG/index.php/IJG/article/view/103/42 > I heard of some tools that can add fiducial marks to digital photographs You can use the photo corners and calculate things yourself using "jhead" or other tools. Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
Le samedi 05 janvier 2008 à 13:44 +0100, Markus Neteler a écrit : > On Jan 5, 2008 1:35 PM, Markus Metz <[EMAIL PROTECTED]> wrote: > ... > > Anyway, digital cameras are apparently not supported in i.ortho.photo. > > Why this? I did so, using a handheld digital camera: > > M. Neteler, D. Grasso, I. Michelazzi, L. Miori, S. Merler, and > C. Furlanello, 2005. An integrated toolbox for image registration, fusion > and classification. International Journal of Geoinformatics. Special Issue > on FOSS/GRASS 2004 & GIS-IDEAS 2004, 1(1), pp. 51-61, March 2005. > PDF: > http://ojs.info.gscc.osaka-cu.ac.jp/IJG/index.php/IJG/article/view/103/42 > > > I heard of some tools that can add fiducial marks to digital photographs > > You can use the photo corners and calculate things yourself using > "jhead" or other tools. You mean pointing corners of the image as four fiducials, then assigning them the dimensions of the sensor, in a coordinate system centered on the estimated principal point ? If you do that with i.ortho.photo what value would you give to the focal length, the one provided by the exif ? Vincent > > Markus > ___ > grass-user mailing list > grass-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-user > ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
On Jan 5, 2008 1:56 PM, Vincent BAIN <[EMAIL PROTECTED]> wrote: > > Le samedi 05 janvier 2008 à 13:44 +0100, Markus Neteler a écrit : > > > On Jan 5, 2008 1:35 PM, Markus Metz <[EMAIL PROTECTED]> wrote: > > ... > > > Anyway, digital cameras are apparently not supported in i.ortho.photo. > > > > Why this? I did so, using a handheld digital camera: > > > > M. Neteler, D. Grasso, I. Michelazzi, L. Miori, S. Merler, and > > C. Furlanello, 2005. An integrated toolbox for image registration, fusion > > and classification. International Journal of Geoinformatics. Special Issue > > on FOSS/GRASS 2004 & GIS-IDEAS 2004, 1(1), pp. 51-61, March 2005. > > PDF: > > http://ojs.info.gscc.osaka-cu.ac.jp/IJG/index.php/IJG/article/view/103/42 > > > > > I heard of some tools that can add fiducial marks to digital photographs > > > > You can use the photo corners and calculate things yourself using > > "jhead" or other tools. > > You mean pointing corners of the image as four fiducials, then assigning > them the dimensions of the sensor, in a coordinate system centered on > the estimated principal point ? If you do that with i.ortho.photo what > value would you give to the focal length, the one provided by the exif ? OK, I have added my draft recipe here: http://grass.gdf-hannover.de/wiki/Orthorectification_digital_camera Feel free to improve the page. Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
Merci ! I'll try it soon... Le samedi 05 janvier 2008 à 14:21 +0100, Markus Neteler a écrit : > On Jan 5, 2008 1:56 PM, Vincent BAIN <[EMAIL PROTECTED]> wrote: > > > > Le samedi 05 janvier 2008 à 13:44 +0100, Markus Neteler a écrit : > > > > > On Jan 5, 2008 1:35 PM, Markus Metz <[EMAIL PROTECTED]> wrote: > > > ... > > > > Anyway, digital cameras are apparently not supported in i.ortho.photo. > > > > > > Why this? I did so, using a handheld digital camera: > > > > > > M. Neteler, D. Grasso, I. Michelazzi, L. Miori, S. Merler, and > > > C. Furlanello, 2005. An integrated toolbox for image registration, > > > fusion > > > and classification. International Journal of Geoinformatics. Special > > > Issue > > > on FOSS/GRASS 2004 & GIS-IDEAS 2004, 1(1), pp. 51-61, March 2005. > > > PDF: > > > http://ojs.info.gscc.osaka-cu.ac.jp/IJG/index.php/IJG/article/view/103/42 > > > > > > > I heard of some tools that can add fiducial marks to digital photographs > > > > > > You can use the photo corners and calculate things yourself using > > > "jhead" or other tools. > > > > You mean pointing corners of the image as four fiducials, then assigning > > them the dimensions of the sensor, in a coordinate system centered on > > the estimated principal point ? If you do that with i.ortho.photo what > > value would you give to the focal length, the one provided by the exif ? > > OK, I have added my draft recipe here: > http://grass.gdf-hannover.de/wiki/Orthorectification_digital_camera > > Feel free to improve the page. > > Markus > ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
> OK, I have added my draft recipe here: > http://grass.gdf-hannover.de/wiki/Orthorectification_digital_camera It says: Usually such high-resolution DEMs (raster cell length below 1m) are not easily available. Therefore, interpolation of a given DEM to a higher resolution is recommended The dem I have is the SRTM data (90m). Eventhough I can interpolate them I don't think it can be useful for i.ortho.photo's purpose. Or is it? >>I once received a script collection to use Octave and GRASS to perform bundle block adjustment but never got that working (still have the code, we could contact the author). Can we use this (SBA)? > Markus > ___ > grass-user mailing list > grass-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-user ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
If you follow Markus' how-to, you may be interested in technical info concerning your camera : Kodak DCS Pro SLR/n/c imager size : 36.0mm x 24.0mm pixel size : 7.9µm x 7.9µm see this page for other cameras : http://www.digitaldingus.com/reference/general/sensorsizes.php Good luck ! Vincent Le samedi 05 janvier 2008 à 23:25 +0800, Maning Sambale a écrit : > Salamat! > > Never expected such quick replies! > > A few more details: > Camera: Kodak Pro DCS 14N digital SLR camera > using a 19-35mm Tamron zoom lens set at 19mm focal length, 13.5 > megapixel resolution (4,500 x 3,000 pixels). > > Images are in Kodak DCR format. Converting to tif before export to > GRASS more than double the size. > > I have the following parameters for each image: > FILENAME > IMAGE NUMBER > DATE > TIME > GPS STATUS > LATITUDE > LONGITUDE > ALTITUDE > ISO SPEED > APERTURE > SHUTTER FOCAL LENGTH > > > unless you use a brute force approach with > > the orthorectified Quickbird imagery, i.e. at least 100 control points > > per image and the strongest rubbersheeting method available. > I think I'd go this route as a last resort, I have approximately 800 > images to rectify. > > > > > http://grass.gdf-hannover.de/wiki/Orthorectification_digital_camera > Thanks for this one > > >> > http://ojs.info.gscc.osaka-cu.ac.jp/IJG/index.php/IJG/article/view/103/42 > > and this one! > > We'll keep you posted as I do this. > > maning > > On Sat, 2008-01-05 at 14:44 +0100, Vincent BAIN wrote: > > Merci ! > > I'll try it soon... > > > > > > Le samedi 05 janvier 2008 à 14:21 +0100, Markus Neteler a écrit : > > > On Jan 5, 2008 1:56 PM, Vincent BAIN <[EMAIL PROTECTED]> wrote: > > > > > > > > Le samedi 05 janvier 2008 à 13:44 +0100, Markus Neteler a écrit : > > > > > > > > > On Jan 5, 2008 1:35 PM, Markus Metz <[EMAIL PROTECTED]> wrote: > > > > > ... > > > > > > Anyway, digital cameras are apparently not supported in > > > > > > i.ortho.photo. > > > > > > > > > > Why this? I did so, using a handheld digital camera: > > > > > > > > > > M. Neteler, D. Grasso, I. Michelazzi, L. Miori, S. Merler, and > > > > > C. Furlanello, 2005. An integrated toolbox for image registration, > > > > > fusion > > > > > and classification. International Journal of Geoinformatics. > > > > > Special Issue > > > > > on FOSS/GRASS 2004 & GIS-IDEAS 2004, 1(1), pp. 51-61, March 2005. > > > > > PDF: > > > > > http://ojs.info.gscc.osaka-cu.ac.jp/IJG/index.php/IJG/article/view/103/42 > > > > > > > > > > > I heard of some tools that can add fiducial marks to digital > > > > > > photographs > > > > > > > > > > You can use the photo corners and calculate things yourself using > > > > > "jhead" or other tools. > > > > > > > > You mean pointing corners of the image as four fiducials, then assigning > > > > them the dimensions of the sensor, in a coordinate system centered on > > > > the estimated principal point ? If you do that with i.ortho.photo what > > > > value would you give to the focal length, the one provided by the exif ? > > > > > > OK, I have added my draft recipe here: > > > http://grass.gdf-hannover.de/wiki/Orthorectification_digital_camera > > > > > > Feel free to improve the page. > > > > > > Markus > > > > > > > ___ > > grass-user mailing list > > grass-user@lists.osgeo.org > > http://lists.osgeo.org/mailman/listinfo/grass-user > > ___ > grass-user mailing list > grass-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-user > ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
Salamat! Never expected such quick replies! A few more details: Camera: Kodak Pro DCS 14N digital SLR camera using a 19-35mm Tamron zoom lens set at 19mm focal length, 13.5 megapixel resolution (4,500 x 3,000 pixels). Images are in Kodak DCR format. Converting to tif before export to GRASS more than double the size. I have the following parameters for each image: FILENAME IMAGE NUMBER DATE TIME GPS STATUS LATITUDE LONGITUDE ALTITUDE ISO SPEED APERTURE SHUTTER FOCAL LENGTH > unless you use a brute force approach with > the orthorectified Quickbird imagery, i.e. at least 100 control points > per image and the strongest rubbersheeting method available. I think I'd go this route as a last resort, I have approximately 800 images to rectify. > > http://grass.gdf-hannover.de/wiki/Orthorectification_digital_camera Thanks for this one >> http://ojs.info.gscc.osaka-cu.ac.jp/IJG/index.php/IJG/article/view/103/42 and this one! We'll keep you posted as I do this. maning On Sat, 2008-01-05 at 14:44 +0100, Vincent BAIN wrote: > Merci ! > I'll try it soon... > > > Le samedi 05 janvier 2008 à 14:21 +0100, Markus Neteler a écrit : > > On Jan 5, 2008 1:56 PM, Vincent BAIN <[EMAIL PROTECTED]> wrote: > > > > > > Le samedi 05 janvier 2008 à 13:44 +0100, Markus Neteler a écrit : > > > > > > > On Jan 5, 2008 1:35 PM, Markus Metz <[EMAIL PROTECTED]> wrote: > > > > ... > > > > > Anyway, digital cameras are apparently not supported in i.ortho.photo. > > > > > > > > Why this? I did so, using a handheld digital camera: > > > > > > > > M. Neteler, D. Grasso, I. Michelazzi, L. Miori, S. Merler, and > > > > C. Furlanello, 2005. An integrated toolbox for image registration, > > > > fusion > > > > and classification. International Journal of Geoinformatics. Special > > > > Issue > > > > on FOSS/GRASS 2004 & GIS-IDEAS 2004, 1(1), pp. 51-61, March 2005. > > > > PDF: > > > > http://ojs.info.gscc.osaka-cu.ac.jp/IJG/index.php/IJG/article/view/103/42 > > > > > > > > > I heard of some tools that can add fiducial marks to digital > > > > > photographs > > > > > > > > You can use the photo corners and calculate things yourself using > > > > "jhead" or other tools. > > > > > > You mean pointing corners of the image as four fiducials, then assigning > > > them the dimensions of the sensor, in a coordinate system centered on > > > the estimated principal point ? If you do that with i.ortho.photo what > > > value would you give to the focal length, the one provided by the exif ? > > > > OK, I have added my draft recipe here: > > http://grass.gdf-hannover.de/wiki/Orthorectification_digital_camera > > > > Feel free to improve the page. > > > > Markus > > > > ___ > grass-user mailing list > grass-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-user ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
Hi, Sat 05 Jan 2008 16:45, Vincent BAIN wrote: > If you follow Markus' how-to, you may be interested in technical info > concerning your camera : > > Kodak DCS Pro SLR/n/c > imager size : 36.0mm x 24.0mm > pixel size : 7.9µm x 7.9µm exactly. even if you (for unknown reasons) do not follow Markus' how-to, you will need this information. and it won't hurt double-checking the correctness of this data against, the DPI in the EXIF data. given that, it's pretty straight-forward to set-up precise fiducial marks. (cf. http://edclxs22.cr.usgs.gov/osl/figure2.gif && http://grass.itc.it/grass63/manuals/html63_user/photo.camera.html ) *but* what is tricky is getting the calibrated focal length right. (and this of course (distortions!) is a quite important parameter) > Le samedi 05 janvier 2008 à 23:25 +0800, Maning Sambale a écrit : > > Camera: Kodak Pro DCS 14N digital SLR camera > > using a 19-35mm Tamron zoom lens set at 19mm focal length ok, his info is not so shabby, at least you know the "calibrated focal length" should be ~19mm. also the spec of the lens should include the focal length tolerance. (aka by how many percent the calibrated focal length is off from the value of 19mm.) cf. http://grass.itc.it/grass63/manuals/html63_user/photo.camera.html && and thread "[CREATE] Lens correction database" @ http://lists.freedesktop.org/archives/create/2007-May/thread.html#743 > > SHUTTER FOCAL LENGTH ?? not quite sure. are these actually to different paramenters, namely the shutter speed && the focal lenght? or what is this?? cheers, s. ps: if anyone knows a good trick to do a precise focal length calibration, plz don't keep it as your secret, but share it with us :)) SCNR. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
On Jan 5, 2008 4:46 PM, Maning Sambale <[EMAIL PROTECTED]> wrote: > > > OK, I have added my draft recipe here: > > http://grass.gdf-hannover.de/wiki/Orthorectification_digital_camera > > It says: > Usually such high-resolution DEMs (raster cell length below 1m) are not > easily available. Therefore, interpolation of a given DEM to a higher > resolution is recommended > > The dem I have is the SRTM data (90m). Eventhough I can interpolate > them I don't think it can be useful for i.ortho.photo's purpose. Or is > it? Well, you have what you have, I think. For which country do you need the DEM? Resampling helps at least to avoid ugly stairs (of course the information content remains the same). > >>I once received a script collection to use Octave and GRASS > to perform bundle block adjustment but never got that working > (still have the code, we could contact the author). > > Can we use this (SBA)? Will write to the author, but my contact is from 2002. Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
Hi Man, not sure if you remember me - we spoke about bundle block adjustment in 2002. There is a recent discussion about this in the GRASS user list and I remembered that I have received "atgrass.tgz" from you. Did you continue to work on this? Best regards Markus Neteler On Jan 5, 2008 5:31 PM, Markus Neteler <[EMAIL PROTECTED]> wrote: > On Jan 5, 2008 4:46 PM, Maning Sambale <[EMAIL PROTECTED]> wrote: > > I once received a script collection to use Octave and GRASS > > to perform bundle block adjustment but never got that working > > (still have the code, we could contact the author). > > > > Can we use this (SBA)? > > Will write to the author, but my contact is from 2002. > > Markus -- Open Source Geospatial Foundation http://www.osgeo.org/ http://www.grassbook.org/ ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
Sat 05 Jan 2008 17:13, sebastian sauer wrote: > Sat 05 Jan 2008 16:45, Vincent BAIN wrote: > > If you follow Markus' how-to, you may be interested in technical info > > concerning your camera : > > > > Kodak DCS Pro SLR/n/c > > imager size : 36.0mm x 24.0mm > > pixel size : 7.9µm x 7.9µm > > exactly. even if you (for unknown reasons) do not follow Markus' how-to, > you will need this information. and it won't hurt double-checking the > correctness of this data against, the DPI in the EXIF data. > > given that, it's pretty straight-forward to set-up precise fiducial > marks. turns out this is essentially known to the experts :) cf. http://www.elcovision.com/e_kamera.html "[DSLRs] have very low deformations; a réseau grid plate for compensation of film or paper deformations is not necessary. For the definition of a photo coordinate system the four photo corners are sufficient. This means: Digital camera do not need to be modified, but can be calibrated and used for measurement as they are." nb.: the markings on a réseau grid plate [0] are the fiducial marks (aka réseau marks.) [0] http://www.elcovision.com/img/Reseauplatte.jpg cf. http://www.ee.oulu.fi/~jth/calibr/ "Modern CCD cameras are usually capable of a spatial accuracy greater than 1/50 of the pixel size." > > (cf. http://edclxs22.cr.usgs.gov/osl/figure2.gif && > http://grass.itc.it/grass63/manuals/html63_user/photo.camera.html ) > > *but* what is tricky is getting the calibrated focal length right. > (and this of course (distortions!) is a quite important parameter) mmh, i'm still skeptical, as i frankly really have no glue how accurate the EXIF data really is. (hints are highly appreciated! e.g. would be interesting if this is within the accuracy of the autofocus error of the lens. ) but according to the experts at least decent DSLR cameras seem to produce a quite accurate EXIF focal length data. cf.: http://www.elcovision.com/e_elco_reseau.html BTW, does anyone know how the EXIF focal length is defined? > > Le samedi 05 janvier 2008 à 23:25 +0800, Maning Sambale a écrit : > > > Camera: Kodak Pro DCS 14N digital SLR camera > > > using a 19-35mm Tamron zoom lens set at 19mm focal length > ok, his info is not so shabby, at least you know the "calibrated focal > length" should be ~19mm. > > also the spec of the lens should include the focal length tolerance. seems which data is hard to get for most (D)SLR lenses. anyway to get a "feeling" what is roughly possible for a single lens. Focal Length Tolerance: ± 0.5 % http://www.rainbowoptics.com/Spherical_Lenses.aspx but of course a (D)SLR lenses is a cascade of many lenses. in professional analgue photogammetry, Focal Length Tolerance: ± 3 mm @153mm (so this should be ~ 4.6 % ) http://erosproject.cr.usgs.gov/osl/reqtable.html BTW, does anyone know what camera-sizes are usually used in aerial photogammetry? aka how big is the plate? medium-size? large-size? > ps: if anyone knows a good trick to do a precise focal length > calibration, plz don't keep it as your secret, but share it with us :)) > SCNR. http://www.google.com/search?hl=en&q=camera+calibration&btnG=Search http://www.stoske.de/digicam/Artikel/verzeichnung.html http://wiki.panotools.org/Lens_correction_model ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
Markus, > Well, you have what you have, I think. For which country do you need > the DEM? Philippines > > >>I once received a script collection to use Octave and GRASS > > to perform bundle block adjustment but never got that working > > (still have the code, we could contact the author). I've been reading through a couple of articles using bundle block adjustment. >From the manual of Leica Photogrammetry Suite: Bundle block adjustment determines the position and orientation for each image in a project as they existed at the time of photographic or image exposure. The resulting parameters are referred to as exterior orientation parameters. In order estimate the exterior orientation parameters, a minimum three GCPs is required for the entire block, regardless of how many images are contained within the project. This maybe what GRASS needs as an additional functionality. cheers, maning ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
On Jan 7, 2008 3:03 PM, Maning Sambale <[EMAIL PROTECTED]> wrote: > Markus, > > > Well, you have what you have, I think. For which country do you need > > the DEM? > Philippines You could also try ASTER DEM (30m). And ask on this mailing list: http://www.osgeo.org/geodata > > > >>I once received a script collection to use Octave and GRASS > > > to perform bundle block adjustment but never got that working > > > (still have the code, we could contact the author). > I've been reading through a couple of articles using bundle block > adjustment. > > >From the manual of Leica Photogrammetry Suite: > Bundle block adjustment determines the position and orientation for each > image in a project as they existed at the time of photographic or image > exposure. The resulting parameters are referred to as exterior > orientation parameters. In order estimate the exterior orientation > parameters, a minimum three GCPs is required for the entire block, > regardless of how many images are contained within the project. > > This maybe what GRASS needs as an additional functionality. I have found the author's recent email address of these BBA scripts, will le you know if he responds. Markus ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] rectifying digital images
Mon 07 Jan 2008 15:45, Markus Neteler wrote: > On Jan 7, 2008 3:03 PM, Maning Sambale <[EMAIL PROTECTED]> wrote: > > >From the manual of Leica Photogrammetry Suite: > > Bundle block adjustment determines the position and orientation for each > > image in a project as they existed at the time of photographic or image > > exposure. The resulting parameters are referred to as exterior > > orientation parameters. In order estimate the exterior orientation > > parameters, a minimum three GCPs is required for the entire block, > > regardless of how many images are contained within the project. > > > > This maybe what GRASS needs as an additional functionality. Maning, c'mon what does this Leica marketing blah-blah help?? if it's *that easy* plz feel free to implement this "additional functionality". actually there exists a pretty nice, quite well known general purpose implementation. http://www.ics.forth.gr/~lourakis/sba/ (maybe OSSIM might have parts of this "additional functionality" implemented.) also somehow, i fear you just don't realize that your images have a very high lens-distortion, while professional arial cameras produce quite rectilinear images. if its of general interest on this mailing-list, i can explain that in detail. (personally i also strongly believe lens correction should *not* become part of the GRASS code-base, as it would a duplication of effort. and very recently there's quite some high-quality knowledge (and even some quite promising code) in the FOSS-community, which would be also perfect for our photogammetric needs.) > I have found the author's recent email address of these BBA scripts, > will le you know if he responds. having this code, would surely not hurt :) cheers, s. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
