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13 th International Scientific and Technical Conference From Imagery to Map: Digital Photogrammetric Technologies. The new methods of dense DTM creation in PHOTOMOD Andrey Sechin Scientific Director, Racurs. September 20 13 , Fontainebleau, France. DEM, DTM, DSM, nDSM. - PowerPoint PPT Presentation
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The new methods of dense DTM creation in PHOTOMOD
Andrey SechinScientific Director, Racurs
September 2013, Fontainebleau, France
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
PHOTOMOD. Different models (depending on algorithm)
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)
Different models for Novokuznetsk city GeoEye-1 stereopair (GSD 0.5m)
Local algorithms of DTM creation
Local algorithms
Memory efficient Fast Subpixel accuracy in
“smooth” regions Problems with periodic
structures and poorly textured regions
Big problem with discontinuities on images
Global algorithms of DTM creation
Global algorithms
Global energy minimization Take into account discontinuities and
hidden surfaces Not memory efficient Still require filtering and smoothing in
the end of algorithm
E = E(data) + E(smooth)
Semi Global Matching (SGM) Graph-cuts Simple Tree Iterative- deformation method
(RACURS)
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
Local vs Global method
SGM andIterative deformation methods
CrossCorrelation
SGM example
Stereopair and disparity map
IDM: GeoEye example
Cross Correlation
IDM
IDM: Pleiades example
IDM: Pleiades example
IDM: DMC aerial example
GSD = 6 cm
IDM: DMC aerial example
GSD = 6 cm
IDM UltraCam example
GSD = 7 cm
RMS difference betweenLIDAR and DSM – 21 cm
IDM UltraCam example
IDM UltraCam example
Thank you for attention
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