The Stereo pair from DTM operation creates a stereo pair from a single raster map and a Digital Terrain Model (DTM).
As input is needed:
Tip: It is highly recommended to select the Interpolation check box in the Properties sheet of your DTM, before you use the Stereo pair from DTM operation.
In the output stereo pair, the input photograph or image is displayed over the terrain. The output stereo pair will contain a left and a right raster map.
You can view the result in stereo, either:
Note: With this operation, stereo vision is only achieved for height differences in terrain. When viewing an output stereo pair, you will not see the heights of objects such as buildings, trees, etc. because these heights are not included in the DTM.
Process and options:
Look angle
The input raster map will be projected twice on the terrain; the input map will be resampled into a left output raster map and a right output raster map. The shift between the left and right output map is determined by the specified look angle. The look angle thus determines the angle by which the left and the right output map are projected over the terrain.
Tips:
Look modus
You can choose to divide this look angle equally over both output maps (look modus Both), i.e. when the look angle is specified as 30°, the left output map will be projected at 15° left over the terrain, and the right output map at 15° right.
You can also choose to look entirely from the left (look modus Left): the left output map will then be projected over the terrain using the total look angle; the right output map will then be projected vertically.
Similarly, when you choose look modus Right, to have the left output map projected vertically, while the right output map is projected over the terrain using the total look angle.
Tip: When you wish to use the output stereo pair for screen digitizing later on, you can use any look modus. After displaying the stereo pair, it does not make a difference whether you screen digitize on the left or on the right output map.
Reference height
You need to provide a reference height, that is the altitude (of the DTM) that should appear at the level of your screen when viewing the stereo pair.
When viewing the stereo pair, larger height values in the DTM will appear 'outside of your monitor', while smaller height values in the DTM will appear 'inside your monitor'.
Objects in a row at reference level in the input map, will end up in the same column in a row of the left and the right output map.
Tip: For the reference height, you can choose for instance, the height of a central well recognizable object in the input photograph/image, the height of an area of interest in the input photograph/image, the average altitude in your DTM, etc.
Resample modus
For the resampling process, you can choose between:
Tip: For more information on accurate resampling methods, see Resample : algorithm.
The left and right output raster map form together the output stereo pair.
Input map requirements:
For the input raster map that will be displayed over the terrain:
The DTM should use a value domain. The area covered by the DTM should preferably be larger than the area covered by the input photograph or image. Only the parts of the photograph or image that also exist in the DTM will be displayed in the output stereo pair.
Note:
To obtain an output stereo pair in which the height differences are continuous, i.e. smoothly spread over the input photograph or image:
Tips:
Output objects:
A dependent stereo pair is created which will contain:
The output stereo pair depends on the input raster map and the DTM.
The output raster maps obtain the same name as the output stereo pair; the left output raster map name is followed by '_Left', the right output raster map name is followed by '_Right'.
The dependency links of the output maps are always broken, so that the output maps are editable.
Tips:
See also:
Stereo pair from DTM : dialog box
Stereo pair from DTM : command line