4.7.5 Stereo-rectification deformation grid generator
Generates two deformation fields to stereo-rectify (i.e. resample in epipolar geometry) a pair of stereo
images up to the sensor model precision
Detailed description
This application generates a pair of deformation grid to stereo-rectify a pair of stereo images
according to sensor modelling and a mean elevation hypothesis. The deformation grids can be
passed to the StereoRectificationGridGenerator application for actual resampling in epipolar
geometry.
Parameters
This section describes in details the parameters available for this application. Table 4.110, page 670
presents a summary of these parameters and the parameters keys to be used in command-line and
programming languages. Application key is StereoRectificationGridGenerator.
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Parameter key | Parameter type |
Parameter description |
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io | Group |
Input and output data |
io.inleft | Input image |
Left input image |
io.inright | Input image |
Right input image |
io.outleft | Output image |
Left output deformation grid |
io.outright | Output image |
Right output deformation grid |
epi | Group |
Epipolar geometry and grid parameters |
epi.elevation | Group |
Elevation management |
epi.elevation.dem | Directory |
DEM directory |
epi.elevation.geoid | Input File name |
Geoid File |
epi.elevation.default | Float |
Default elevation |
epi.elevation.avgdem | Group |
Average elevation computed from DEM |
epi.elevation.avgdem.step | Int |
Sub-sampling step |
epi.elevation.avgdem.value | Float |
Average elevation value |
epi.elevation.avgdem.mindisp | Float |
Minimum disparity from DEM |
epi.elevation.avgdem.maxdisp | Float |
Maximum disparity from DEM |
epi.scale | Float |
Scale of epipolar images |
epi.step | Int |
Step of the deformation grid (in nb. of
pixels) |
epi.rectsizex | Int |
Rectified image size X |
epi.rectsizey | Int |
Rectified image size Y |
epi.baseline | Float |
Mean baseline ratio |
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inverse | Group |
Write inverse fields |
inverse.outleft | Output image |
Left inverse deformation grid |
inverse.outright | Output image |
Right inverse deformation grid |
inverse.ssrate | Int |
Sub-sampling rate for inversion |
inxml | XML input parameters file |
Load otb application from xml file |
outxml | XML output parameters file |
Save otb application to xml file |
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Table 4.110: Parameters table for Stereo-rectification deformation grid generator.
Input and output data
This group of parameters allows to set the input and output images.
- Left input image: The left input image to resample
- Right input image: The right input image to resample
- Left output deformation grid: The output deformation grid to be used to resample the left
input image
- Right output deformation grid: The output deformation grid to be used to resample the
right input image
Epipolar geometry and grid parameters
Parameters of the epipolar geometry and output grids
- Elevation management: This group of parameters allows to manage elevation values. Supported
formats are SRTM, DTED or any geotiff. DownloadSRTMTiles application could be a useful tool to
list/download tiles related to a product.
- DEM directory: This parameter allows to select a directory containing Digital
Elevation Model tiles
- Geoid File: Use a geoid grid to get the height above the ellipsoid in case
there is no DEM available, no coverage for some points or pixels with no_data
in the DEM tiles. A version of the geoid can be found on the OTB website
(http://hg.orfeo-toolbox.org/OTB-Data/raw-file/404aa6e4b3e0/Input/DEM/egm96.grd).
- Default elevation: This parameter allows to set the default height above ellipsoid when
there is no DEM available, no coverage for some points or pixels with no_data in the
DEM tiles, and no geoid file has been set. This is also used by some application as an
average elevation value.
- Average elevation computed from DEM: Average elevation computed from the provided
DEM
- Sub-sampling step: Step of sub-sampling for average elevation estimation
- Average elevation value: Average elevation value estimated from DEM
- Minimum disparity from DEM: Disparity corresponding to estimated minimum
elevation over the left image
- Maximum disparity from DEM: Disparity corresponding to estimated maximum
elevation over the left image
- Scale of epipolar images: The scale parameter allows to generated zoomed-in (scale <1) or
zoomed-out (scale >1) epipolar images.
- Step of the deformation grid (in nb. of pixels): Stereo-rectification deformation grid only varies
slowly. Therefore, it is recommanded to use a coarser grid (higher step value) in case of large
images
- Rectified image size X: The application computes the optimal rectified image size so that the whole
left input image fits into the rectified area. However, due to the scale and step parameter, this size may
not match the size of the deformation field output. In this case, one can use these output
values.
- Rectified image size Y: The application computes the optimal rectified image size so that the whole
left input image fits into the rectified area. However, due to the scale and step parameter, this size may
not match the size of the deformation field output. In this case, one can use these output
values.
- Mean baseline ratio: This parameter is the mean value, in pixels.meters−1, of the baseline to sensor
altitude ratio. It can be used to convert disparities to physical elevation, since a disparity of one pixel
will correspond to an elevation offset of the invert of this value with respect to the mean
elevation.
Write inverse fields
This group of parameter allows to generate the inverse fields as well
- Left inverse deformation grid: The output deformation grid to be used to resample the
epipolar left image
- Right inverse deformation grid: The output deformation grid to be used to resample the
epipolar right image
- Sub-sampling rate for inversion: Grid inversion is an heavy process that implies spline
regression on control points. To avoid eating to much memory, this parameter allows to first
sub-sample the field to invert.
Load otb application from xml file
Load otb application from xml file
Save otb application to xml file
Save otb application to xml file
Example
To run this example in command-line, use the following:
otbcli_StereoRectificationGridGenerator -io.inleft wv2_xs_left.tif -io.inright wv2_xs_left.tif -io.outleft wv2_xs_left_epi_field.tif -io.outright wv2_xs_right_epi_field.tif -epi.elevation.default 400
To run this example from Python, use the following code snippet:
#!/usr/bin/python # Import the otb applications package import otbApplication # The following line creates an instance of the StereoRectificationGridGenerator application StereoRectificationGridGenerator = otbApplication.Registry.CreateApplication("StereoRectificationGridGenerator") # The following lines set all the application parameters: StereoRectificationGridGenerator.SetParameterString("io.inleft", "wv2_xs_left.tif") StereoRectificationGridGenerator.SetParameterString("io.inright", "wv2_xs_left.tif") StereoRectificationGridGenerator.SetParameterString("io.outleft", "wv2_xs_left_epi_field.tif") StereoRectificationGridGenerator.SetParameterString("io.outright", "wv2_xs_right_epi_field.tif") StereoRectificationGridGenerator.SetParameterFloat("epi.elevation.default", 400) # The following line execute the application StereoRectificationGridGenerator.ExecuteAndWriteOutput()
Limitations
Generation of the deformation grid is not streamable, pay attention to this fact when setting the grid
step.
Authors
This application has been written by OTB-Team.
See also
These additional ressources can be useful for further information:
- otbGridBasedImageResampling