Re: [gdal-dev] How to apply a costum shift grid?
Hi Frederick, On Wed, Jun 29, 2011 at 1:25 AM, frederick keusch frederick.keu...@digimapas.cl wrote: I am working here in Chile and we have a lot of earthquakes here, the last big one like a year ago. So the problem is that I have a lot of georeferenced images, but georeferenced before the earthquake. We thought the best way would be to calculate a shift grid and apply it with gdalwarp to all of the images. The only thing I would have to do is to apply the grid from one datum to the same datum instead of from one datum to another, this should be possible, shouldn´t it? Yeah. I'm assuming you know that the grid shifts are applied as a transform on the geocentric coordinates? Reading a lot in the mailing-list I found a link to an australian govermental site, where they provide a program to convert from NTv2_ASCII to NTv2_GSB. So I created an Ntv2_ASCII file with our shift values and converted it with this program to an .gsb-file and tried to apply that file with gdalwarp to our images. But no matter what I tried, nothing happened, the shift never was applied. I saw a lot of examples of possible commands searching in the mailing-list and tried everyone, also in nearly every possible combination but nothing lead to an applied shift. So I am a bit desperate right now, hoping someone can help me a bit or give an advice. Here in short what I have to do: Apply a shift grid from UTM 18s WGS84 to UTM 18s WGS84 in order to apply the coordinate changes of our images owing of the earthquake last year. I would apreciate any kind of help and thank a lot in advance, First I'd get your grid working with proj4/cs2cs: See how it's setup for the US/NZ/CA grids that are available as a companion download http://trac.osgeo.org/proj/wiki/GenParms describes the +nadgrids parameter to tell proj4 to use it during datum shift. Once that's all working... In the gdal python bindings you need to add +wktext to the end of your proj4 string to get it to recognise/use grids. Hope that helps a bit, Rob :) ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
[gdal-dev] How to apply a costum shift grid?
Hi, I am working here in Chile and we have a lot of earthquakes here, the last big one like a year ago. So the problem is that I have a lot of georeferenced images, but georeferenced before the earthquake. We thought the best way would be to calculate a shift grid and apply it with gdalwarp to all of the images. The only thing I would have to do is to apply the grid from one datum to the same datum instead of from one datum to another, this should be possible, shouldn´t it? Reading a lot in the mailing-list I found a link to an australian govermental site, where they provide a program to convert from NTv2_ASCII to NTv2_GSB. So I created an Ntv2_ASCII file with our shift values and converted it with this program to an .gsb-file and tried to apply that file with gdalwarp to our images. But no matter what I tried, nothing happened, the shift never was applied. I saw a lot of examples of possible commands searching in the mailing-list and tried everyone, also in nearly every possible combination but nothing lead to an applied shift. So I am a bit desperate right now, hoping someone can help me a bit or give an advice. Here in short what I have to do: Apply a shift grid from UTM 18s WGS84 to UTM 18s WGS84 in order to apply the coordinate changes of our images owing of the earthquake last year. I would apreciate any kind of help and thank a lot in advance, Frederick -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/How-to-apply-a-costum-shift-grid-tp6524901p6524901.html Sent from the GDAL - Dev mailing list archive at Nabble.com. ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] How to apply a costum shift grid?
Frederick, I'm a geophysicist but never thought that an earthquake could have that side effect of image referencing. Anyway the horizontal deformation caused by a big earthquake is of the order of meter scale. One idea I had is that you can use the shift grid to to relocate previous GCPs and than use those relocated ones in gdalwarp. You can compute 'old' GCPs by interpolating your images both for pixels and metric (UTM) units. The operations would be something like this 1. Get px py old_UTMx old_UTMy by interpolating the referenced image at a certain well distributed positions 2. apply the shift grid to old GCPs and get new GCPs px py new_UTMx new_UTMy 2. re-register with gdalwarp and new GCPs Of course, this is in absence of a more straight solution where the shift grid is applied directly to the images. Joaquim Luis Hi, I am working here in Chile and we have a lot of earthquakes here, the last big one like a year ago. So the problem is that I have a lot of georeferenced images, but georeferenced before the earthquake. We thought the best way would be to calculate a shift grid and apply it with gdalwarp to all of the images. The only thing I would have to do is to apply the grid from one datum to the same datum instead of from one datum to another, this should be possible, shouldn´t it? Reading a lot in the mailing-list I found a link to an australian govermental site, where they provide a program to convert from NTv2_ASCII to NTv2_GSB. So I created an Ntv2_ASCII file with our shift values and converted it with this program to an .gsb-file and tried to apply that file with gdalwarp to our images. But no matter what I tried, nothing happened, the shift never was applied. I saw a lot of examples of possible commands searching in the mailing-list and tried everyone, also in nearly every possible combination but nothing lead to an applied shift. So I am a bit desperate right now, hoping someone can help me a bit or give an advice. Here in short what I have to do: Apply a shift grid from UTM 18s WGS84 to UTM 18s WGS84 in order to apply the coordinate changes of our images owing of the earthquake last year. I would apreciate any kind of help and thank a lot in advance, Frederick -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/How-to-apply-a-costum-shift-grid-tp6524901p6524901.html Sent from the GDAL - Dev mailing list archive at Nabble.com. ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
