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DEM Extraction ResultsGeomatica 2015
Work Performed in this release• 2x to 4x improvement in DEM extraction performance• Special handling of high-res satellites• Improved correlation: Fewer blunders and failed areas• Sharper edges, more detail• Better handling of rapid changes in elevation (steep
slopes, tops of tall buildings)• New smoothing filters that preserve detail• Improved merging of tri-stereo DEMs
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Performance Improvements
• DEM extraction specifically improved (epi-polar generation and geocoding unchanged)
• With all steps included total times are 1.5x to 2x faster
Source Original Current Improvement
Ultracam airphoto 160s 40s 4x
World View 2 (hi-res satellite) 35m 11m 3x
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WV-2 50cm ortho-image of Greenland
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WV-2 2m DTM of Greenland
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High-Res Satellites• Sub-metre (50cm and below) satellites
– e.g. GeoEye 2, WorldView 3• Now using methodologies similar to aerial
photography• Higher detail and fewer blunders than
previous methods
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GeoEye 2 (50cm Satellite)• 50cm, 1m and 2m DEMs extracted automatically• No manual editing was performed• Control was a single GCP yielding 10cm
accuracy• Subject area is a mining site with high relief
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• Full DEM shown at left• 34k x 53k pixels• 17km x 26km area• Note high detail at
50cm DEM• Red box indicates
study area8
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Mining site – GeoEye 2 image at 50cm
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Mining site – GeoEye 2 DEM at 2m
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Mining site – GeoEye 2 DEM at 1m
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Mining site – GeoEye 2 DEM at 50cm (1 point-per-pixel density)
World View 3 (30cm Satellite)• 30cm and 60cm DEMs extracted automatically• Water areas were manually flattened. No other
editing was performed• No GCPs: Geometry based on ephemeris and
tie-points only• Subject area is a new volcanic island in the
South Pacific ocean
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Volcano – WV3 DEM using older extraction method
Note many blunders/failures and lack of detail
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Volcano – WV3 DEM at 30cm using current extraction method
Fewer blunders and higher detail in less time
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Volcano – WV3 imagery at 30cm
Comparison of DEM and image results
Before & after eruption (via BBC News)
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Air Photo• 20cm DEM extracted automatically from
10cm imagery• Better detail, fewer failures
– Buildings have sharper edges– Captures tops of high buildings– Smoother roads and surfaces
• 3x faster18Copyright PCI Geomatics 2015
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20cm DSM overview 20cm DSM detail (raw, unedited)
UltraCam 30cm DSM of Graz, Austria
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UltraCam 7.5cm ortho-image of Graz, Austria
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220-image, 15cm UltraCam project: 30cm DSM overview
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220-image, 15cm UltraCam project: 30cm DSM detail
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220-image, 15cm UltraCam project: 30cm DSM detail
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220-image, 15cm UltraCam project: 30cm DSM detail (maximum zoom)
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220-image, 15cm UltraCam project: Image detail
Contact PCI Geomatics
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