The new methods of dense DTM creation in PHOTOMOD Andrey Sechin Scientific Director, Racurs September 2013, Fontainebleau, France
Dec 25, 2015
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