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#### 4.7.2 Disparity map to elevation map

Projects a disparity map into a regular elevation map

##### Detailed description

This application uses a disparity map computed from a stereo image pair to produce an elevation map on the ground area covered by the stereo pair. The needed inputs are : the disparity map, the stereo pair (in original geometry) and the epipolar deformation grids. These grids have to link the original geometry (stereo pair) and the epipolar geometry (disparity map).

##### Parameters

This section describes in details the parameters available for this application. Table 4.39, page 454 presents a summary of these parameters and the parameters keys to be used in command-line and programming languages. Application key is DisparityMapToElevationMap.

Parameter key | Parameter type | Parameter description

io | Group | Input and output data
io.in | Input image | Input disparity map
io.left | Input image | Left sensor image
io.right | Input image | Right sensor image
io.lgrid | Input image | Left Grid
io.rgrid | Input image | Right Grid
io.out | Output image | Output elevation map
io.mask | Input image | Disparity mask
step | Float | DEM step
hmin | Float | Minimum elevation expected
hmax | Float | Maximum elevation expected
elev | Choices | Elevation management
elev dem | Choice | DEM directory
elev average | Choice | Average Elevation
elev.dem.path | Directory | DEM directory
elev.dem.geoid | Input File name | Geoid File
elev.average.value | Float | Average Elevation
ram | Int | Available RAM (Mb)

Table 4.39: Parameters table for Disparity map to elevation map.

Input and output data This group of parameters allows to set the input and output images and grids.

- Input disparity map: The input disparity map (horizontal disparity in first band, vertical in second)
- Left sensor image: Left image in original (sensor) geometry
- Right sensor image: Right image in original (sensor) geometry
- Left Grid: Left epipolar grid (deformation grid between sensor et disparity spaces)
- Right Grid: Right epipolar grid (deformation grid between sensor et disparity spaces)
- Output elevation map: Output elevation map in ground projection
- Disparity mask: Masked disparity cells won’t be projected

DEM step Spacing of the output elevation map (in meters)

Minimum elevation expected Minimum elevation expected (in meters)

Maximum elevation expected Maximum elevation expected (in meters)

Elevation management This group of parameters allows to manage elevation values. Supported formats are SRTM, DTED or any geotiff processed by the DEM import application Available choices are:

- DEM directory
  - 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 used
- Average Elevation
  - Average Elevation: This parameter allows to pick up an average elevation for all the points of the image.

Available RAM (Mb) Available memory for processing (in MB)

##### Example

To run this example in command-line, use the following:

otbcli_DisparityMapToElevationMap -io.in disparity.tif -io.left sensor_left.tif -io.right sensor_right.tif -io.lgrid grid_epi_left.tif -io.rgrid grid_epi_right.tif -io.out dem.tif

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 DisparityMapToElevationMap application
DisparityMapToElevationMap = otbApplication.Registry.CreateApplication("DisparityMapToElevationMap")
# The following lines set all the application parameters:
DisparityMapToElevationMap.SetParameterString("io.in", "disparity.tif")
DisparityMapToElevationMap.SetParameterString("io.left", "sensor_left.tif")
DisparityMapToElevationMap.SetParameterString("io.right", "sensor_right.tif")
DisparityMapToElevationMap.SetParameterString("io.lgrid", "grid_epi_left.tif")
DisparityMapToElevationMap.SetParameterString("io.rgrid", "grid_epi_right.tif")
DisparityMapToElevationMap.SetParameterString("io.out", "dem.tif")
# The following line execute the application
DisparityMapToElevationMap.ExecuteAndWriteOutput()

##### Limitations

None

##### Authors

This application has been written by OTB-Team.

##### See also

These additional ressources can be useful for further information:

- otbStereoRectificationGridGenerator otbBlockMatching

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