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Using Reference3D in mapping projects. L. Falala IGN France International. Medium-scale cartography from 1/250,000 to 1/100,000. Simple process: Global DEM like SRTM or Reference3D: 30-90m resolution Medium resolution satellite images like Spot5 or Rapideye : 2.5-10m resolution - PowerPoint PPT Presentation
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Using Reference3D in mapping projects
L. Falala
IGN France International
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Medium-scale cartography from 1/250,000 to 1/100,000
Simple process:- Global DEM like SRTM or Reference3D: 30-90m resolution- Medium resolution satellite images like Spot5 or Rapideye: 2.5-10m resolution- Orthorectification of satellite images- Plotting of Geodatabase features directly on orthoimages- Map edition
Altimetric layer: Global DEM- SRTM: from 56º South to 60º North, 3” resolution (90m), freely distributed- ASTER GDEM: 99% of land areas, 1” resolution (30m), freely distributed- Reference3D: >50M km2, 1” resolution (30m), public price: 2-3 US$/km2
Cheap process: a few US$/km2 for data + processing costs
Is it accurate enough for medium-scale cartography ?
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Impact of DEM accuracy on map quality
Planimetric accuracy of orthoimages depends on:
- Ground control points- DEM accuracy
DEM accuracy:- SRTM: 16m at 90%- Reference3D: 10m at 90%
Orthoimages:- Plani error < 20m with viewing angle < 40º
Map Scale 1/250,000 1/200,000 1/100,000
Data planimetric accuracy 50m 40m 20m
Paper Map accuracy: 0.2mm
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Impact of DEM accuracy on map quality
Spot heights: altimetric accuracy = DEM accuracy
Contour interval must be aligned with DEM accuracy:- 20m interval minimum with SRTM and Reference3D
Hill shading and contour lines quality depends on:- Accurate rendering of local shapes in DEM: no blocked valleys, no rounded crests lines
- Absence of artefacts in DEM (SRTM void data)
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New 1/200K maps of Senegal
“PCS200” project: - Conducted in 2004-2008 by IGN-FI and mapping agency of Senegal- Financed by European Union- Production of a GeoDatabase and 27 new maps at 1/200,000
Methodology:- Altimetric reference layer: Reference3D DEM - Orthoimages calculated from Spot 5 panchromatic images at 5m and Landsat colour images at 30m
- Spot heights interpolated from DEM and distributed every 10km- Hill shading image calculated from Reference3D- Contour lines with 20m interval automatically extracted from Reference3D, automatically smoothed and manually edited
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New 1/200K maps of Senegal
30m Reference3D DEM 20m interval contour lines
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New 1/200K maps of Senegal
Hill shading from Reference3D DEM
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New 1/200K maps of Senegal
No GCPs coming from existing maps or field survey Only tie points with Reference3D
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New 1/200K maps of Senegal
Checking accuracy:- GPS points and GPS recordings of vehicles during field completion phase - Consistency of maps and GPS always better than 15m
Success of the project:- 27 maps produced in due time and within specifications- Inexpensive data + simple methodology- Know-how transfer to local institutions- EU is funding comparable mapping project in Burkina Faso in 2011
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Old and new map of Kolda (extract)
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Old and new map of Nioro du Rip (extract)
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Old and new map of Kaffrine (extract)
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Mosaic of the 27 new maps
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Conclusion
For Medium Scale Mapping, altimetric layer can come from Reference3D
Whatever the mapping project: do not understate 3D information- Impact on what you put on the map- Impact on map accuracy
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IGN France International39 ter, rue Gay Lussac - 75005 PARISFrance
Tél : +33 1 42 34 56 56Fax : +33 1 42 34 56 [email protected] - www.ignfi.fr
IGN France International8 rue du Sentier - 75002 PARISFrance
Tél : +33 1 42 34 56 56Fax : +33 1 42 34 56 [email protected] - www.ignfi.com
Thank you for your attention
Laurent Falala: [email protected]
