Advances in DTM Creation and Processing Methods in PHOTOMOD 5 Alexey Elizarov Deputy Head of Software Development Department September 2010, Gaeta, Italy X th International Scientific and Technical Conference From Imagery to Map: Digital Photogrammetric Technologies

DTM Creation Typical DTM step of about 10—100 metres Correlator-based algorithm for corresponding point search on a pair of images PHOTOMOD 4.x → 5.0 improvements: Significant improvement of corresponding point search algorithm to increase robustness of the obtained heights. Search in triple overlap areas and inter-strip stereopairs followed by automatic filtering of excessively dense points. PHOTOMOD 5.0 → 5.1 improvements: see the slides to follow...

DTM Computation Interface Simplified DTM computation setup window Presets for the most common terrain and imagery types:  rural  urban  mountainous ...

Height Computation for Linear Objects Problem When correlation coefficient reaches its maximum on a straight line, no certain point match can be found......if we have no additional information.

Height Computation for Linear Objects PHOTOMOD 5.0PHOTOMOD 5.1 in-strip stereopair epipolar line direction Corresponding point search on epipolar lines Robust height determining for linear objects directed at large angles to epipolar lines Points on linear objects are discarded as unreliable.

Height Computation for Linear Objects epipolar line direction PHOTOMOD 5.1 inter-strip stereopair PHOTOMOD 5.1 all stereopairs Inter-strip stereopairs give heights of objects that are “weak” in in-strip stereopairs. Processing all stereopairs gives heights of all objects (a case of multiimage matching).

Buildings and Vegetation Filter Removes points on non-terrain objects such as buildings, plants.  Yellow points: “good” points left by the filter.  Red points: “bad” points removed by the filter.

Dense DTM Dense DTM step is nearly equal to the imagery GSD. Dense DTM creation steps: 1.Computation of a preliminary dense DEM 2.Filtering the preliminary DEM 3.Interpolating the DEM Dense DTM creation is accomplished by: New correlator-based algorithm of fast computation of dense model Uses benefits of NVidia CUDA technology of GPGPU parallel computations: 17 megapixels per minute on Tesla C1060 / Quadro FX5800. Dense model filtration algorithm Dense model interpolation algorithm Dense DTM allows more accurate filtering out non-terrain objects.

Dense DTM Creation Preliminary dense DEM Filtered DEM Interpolated DEM Excessive details Higher quality

High Quality Smooth Contour Lines

Laser Scanner Data Import from LAS files Unlimited data volume Area of interest selection Possibility to split the result into sheets

Further Development of DTM Creation Methods Moving to image recognition approaches. Techniques: Dynamic programming Signal filtration theory Advantages: Increasing accuracy Increasing robustness DSM creation Automation of object extraction and classification

Thank you for attention!