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Ortho Rectification of google images


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  • 2 weeks later...

but if do you need orthorectification its should have overlay amount the imagery ...and then will need control ground point for make the orthorectifiction process....need more elements like focal distance, and other ...if you speak of orthorectification ...but is georeferencing there change the process....pleas be clear what really want for help in this direction.

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  • 1 month later...

Google images are already rectified, but only from a terrain point of view... of course this is not true orthophoto (the one you mean by viewing the buildings from the top)... you won't be able to do what you're looking for, you would need at least a pair of stereo images in order to extract a DEM that would allow you to produce a true ortho, lidar data would be better.

My tip : considering that the ground surface is ± rectified, draw your footprint from the base of the buildings and guess the 4th point (hidden by the tilted building) according to the apparent building geometry and 90° angles in most of the cases. Of course this is real approximate job, considering the georeferencing of google images which is sometimes strange... then again it depends on the imagery quality in the area you're working on.

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  • 11 months later...
  • 5 weeks later...
  • 4 weeks later...

@atul_salunke

Ortho rectification is a proces in photogrammetry that converts 3D image to ortho projection, no 2D image to 2D image. To get 3D image from a stereo pair, you should have as many GCPs as possible to drape this image precisely to the terrain.

Once I did a job of stiching simple aerophotos (not stereo pairs, but images of 10% overlap) by rectifying them, but that was long lasting job in urban areas with high buildings. I used polinomal rectification in Raster Design. Always save points and keep original image files. After rectification you may see some mistakes in final image. Then you should add even more control points in the areas with mistakes and process agein. And all the way until you are sattisfied with the result.

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