Frequently Asked Questions
Input data
How to create CARS compatible ROI input data with OTB ?
CARS supports the ROI products extracts done with the otbcli_ExtractROI OTB application (raster + geometric model).
First, retrieve the coordinates of the desired extract on the first image (lets call it
img1.jp2), under the formstartx,starty,sizex,sizey(in pixels).Perform the extraction of the first image with:
$ otbcli_ExtractROI -in img1.jp2 -out img1_xt.tif uint16 -startx startx -starty starty -sizex sizex -sizey sizey
Extract the same zone on the second image (for example
img2.jp2), the-mode fitapplication option has to be used:
$ otbcli_ExtractROI -in img2.jp2 -out img2_xt.tif uint16 -mode fit -mode.fit.im img1_xt.tif
The application will automatically look for the zone corresponding to img1_xt.tif within img2.jp2.
It is possible to use the -elev.dem srtm/ option to use the DEM during this search in order to be more accurate.
It is to be noted that the -mode.fit.vec option also exists. It accepts a vector file (for example a shapefile or a kml) which enables the image extraction from a footprint.
How to generate input images in epipolar geometry from grids ?
To generate the images in epipolar geometry from the grids computed by cars and the original images, one can refer to the Orfeo Toolbox documentation here .
Output data
How to generate output files overview ?
Considering bulky files, it can be recommended to generate an overview file with GDAL before opening it with QGIS:
$ gdaladdo -ro -r average dsm.tif 2 4 8 16 32 64