Transcript 14th International Scientific and Technical Conference From Imagery to Map: Digital Photogrammetric Technologies Dense DSM Generation Module in PHOTOMOD 6.0 Andrey Sechin Scientific Director, Racurs October 2014,

14th International Scientific and Technical Conference
From Imagery to Map: Digital Photogrammetric Technologies
Dense DSM
Generation Module in
PHOTOMOD 6.0
Andrey Sechin
Scientific Director, Racurs
October 2014, Hainan, China
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DEM, DTM, DSM, nDSM
DEM, DTM have different definitions in different countries.
In Russian (по-русски) ЦМР, ЦМП
DEM & DTM - bare earth terrain. DSM include tree canopy &
buildings.
nDSM = DSM - DTM
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PHOTOMOD. Different models (depending on algorithm)
Different models for Novokuznetsk city
GeoEye-1 stereopair (GSD 0.5m)
 Automatic DSM (old cross-correlation algorithm) with filtering buildings and
trees
 Automatic DSM (old cross-correlation algorithm)
 3D semi-automatic model (with manual stereo vectorization)
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Local algorithms of DTM creation
Memory efficient
Fast
Subpixel accuracy in
“smooth” regions
Problems with periodic
structures and poorly textured
regions
Big problem with
discontinuities on images
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Global algorithms of DSM creation
Global energy minimization
Take into account discontinuities and hidden
surfaces
Not memory efficient
Still require filtering and smoothing in the end
of algorithm
Semi Global Matching (SGM)
Graph-cuts
Simple Tree
Iterative- deformation method (RACURS)
E = E(data) + E(smooth)
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Local vs Global method
CrossCorrelation
SGM and
Iterative deformation
methods
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PHOTOMOD: iterative deformation method (IDM)
All images are taken into account
simultaneously
Memory efficient
Image pyramid hierarchy is used for
speed and reliability
Image resection is used to calculate
occlusions
Still requires filtering and smoothing on
the final step
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PHOTOMOD: iterative deformation method (IDM)
1-st image
2-nd image
height
approximation
levels
orthophoto
DSM
Point with unknown
height
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IDM vs SGM
We used SURE (Institute for Photogrammetry (IfP), University of
Stuttgart) as SGM example
SGM is faster (20-30%) on the local computer
IDM is faster in the network environment (parallel
computing based on images + dsm levels and area splitting)
IDM does not need epipolar geometry
IDM uses all images simultaneously
IDM uses different strategies based on the DSM guess
IDM uses elements of pattern recognition for different
height approximations
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PHOTOMOD 6.0 - User interface
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IDM: GeoEye example
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IDM: GeoEye example
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IDM: WorldView 1 example
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IDM: WorldView 1 example
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IDM: UltraCam example
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IDM: UltraCam example
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IDM: UltraCam example
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IDM: DMC example (Munich block)
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www.racurs.r
u
IDM: DMC example
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www.racurs.r
u
Thank you
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www.racurs.r
u