StereoRectificationGridGenerator - 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 [1] presents a summary of these parameters and the parameters keys to be used in command-line and programming languages. Application key is StereoRectificationGridGenerator .

[1]Table: Parameters table for Stereo-rectification deformation grid generator.
Parameter Key Parameter Name Parameter Type
io Input and output data Group
io.inleft Left input image Input image
io.inright Right input image Input image
io.outleft Left output deformation grid Output image
io.outright Right output deformation grid Output image
epi Epipolar geometry and grid parameters Group
epi.elevation Elevation management Group
epi.elevation.dem DEM directory Directory
epi.elevation.geoid Geoid File Input File name
epi.elevation.default Default elevation Float
epi.elevation.avgdem Average elevation computed from DEM Group
epi.elevation.avgdem.step Sub-sampling step Int
epi.elevation.avgdem.value Average elevation value Float
epi.elevation.avgdem.mindisp Minimum disparity from DEM Float
epi.elevation.avgdem.maxdisp Maximum disparity from DEM Float
epi.scale Scale of epipolar images Float
epi.step Step of the deformation grid (in nb. of pixels) Int
epi.rectsizex Rectified image size X Int
epi.rectsizey Rectified image size Y Int
epi.baseline Mean baseline ratio Float
inverse Write inverse fields Group
inverse.outleft Left inverse deformation grid Output image
inverse.outright Right inverse deformation grid Output image
inverse.ssrate Sub-sampling rate for inversion Int
inxml Load otb application from xml file XML input parameters file
outxml Save otb application to xml file XML output parameters file

[Input and output data]: This group of parameters allows setting 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 managing 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 selecting a directory containing Digital Elevation Model files. Note that this directory should contain only DEM files. Unexpected behaviour might occurs if other images are found in this directory.
  • 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 setting 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 generating 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 recommended 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 generating 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 one 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 resources can be useful for further information:

otbGridBasedImageResampling