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Figure 2. UltraMap concept and modules.
With the upcoming version of UltraMap 3.0 two new
modules will be added to further extend the workflow.
These two modules provide revolutionary new features,
namely the automated generation of point clouds, digital
surface models (DSM), digital terrain models (DTM),
DSMOrtho images and DTM Ortho images, all derived
from a set of overlapping UltraCam images. Results from
the basic image processing and the aero triangulation are
used by the new modules to generate a point cloud, then a
DSM, then a DTM and then two different ortho images, the
so called DSMOrtho (images rectified by a DSM) and
DTMOrtho (images rectified by the DTM).
UltraMap
, MitraMap/AT
DTM
Figure 3. New UltraMap 3.0 modules
The processing is being kicked-off automatically after the
aero triangulation and fully supports the automated
distributed processing and the full 16-bit workflow. The
new modules support processing on GPU(s) if available in
the system. Visual output and QC are smoothly integrated
into the existing viewer.
2. Dense Matching and 3D Point Clouds
A significant change in photogrammetry has been achieved
by Multi-Ray Photogrammetry which became possible high
performance digital aerial camera such as UltraCam and a
fully digital workflow by software systems such as
UltraMap. The cameras enable a significantly increased
forward overlap as well as the ability to collect more
images but literally without increasing acquisition costs.
These highly redundant image datasets enable to generate
new products such as point clouds highly automated and
robust.
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However, Multi-Ray Photogrammetry in a first step is not a
new technology; it is a specific flight pattern with a very
high forward overlap (8096, even 9096) and an increased
sidelap (up to 6096). The result is this highly redundant
dataset that allows automated “dense matching” to generate
high resolution, highly accurate point clouds from the
imagery by matching the pixels of the overlapping images
automatically.
For the point cloud generation, the dense matcher analyzes
the images and calculates a range image for each pixel on
the ground from each stereo pair covering the pixel on the
ground. The location (x, y,) of the pixel is defined by its
position in the geo-referenced image; the range image
defines a z-value for each pixel. Due to the highly
redundant data set (thanks to the high forward and sidelap),
usually multiple stereo pairs exist which cover one pixel on
the ground. Thus multiple range images can be processed
by the dense matcher who leads to multiple z-vales per
pixel. That makes the whole process very robust and
increases accuracy of the derived z-value.
The 3D point cloud generated by the dense matcher of
UltraMap has a point density of several hundred points per
square meter and thus is much denser than any airborne
Lidar scanning point cloud.
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