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 fit
application 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