Reference3D
Your geographic reference system
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Developed in partnership by Spot Image and the French survey and mapping agency IGN, Reference3D is a geocoded database containing three layers of information:
- a DTED level 2 HRS DEM
- GPS-compatible HRS Orthoimage
- quality and traceability metadata
Reference3D is the keystone of any application that calls for very-high-accuracy elevation data.
Reference3D is unrivalled in the world for accuracy, coverage, with more than 15 million km² already covered (50 million km² by 2009).
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DEM
These files contain a uniform grid of terrain elevation values of an area of interest and are obtained through automatic correlation of SPOT HRS stereopairs.
- Sampling step: 1 second of arc (~ 30 m at the equator, varying according to latitude)
- Absolute elevation accuracy: 10 m @ 90% for a slope < 20°
- Absolute planimetric accuracy: 15 m @ 90%
HRS orthoimages
These images are orthorectified from the DEM and have a high degree of geometric quality and location accuracy
- Absolute planimetric accuracy: 16 m @ 90%
- Sampling step: 1/6 second of arc (~ 5 m at the equator - varying according to latitude)
Quality and traceability data
- These are quality indicators for data sources and provide references and footprints for DEMs and orthoimages,
- They describe the processing done for producing DEMs (masks),
- They give accuracy estimates.
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Size
Reference3D comes in geographic tiles of 1°x 1° covering emerged land areas and aligned along parallels and meridians.
The surface area of a tile, equivalent to 111 km x 111 km at the equator, decreases as the latitude increases.
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Format / Delivery
Reference3D comes in a DIMAP format.
The HRS DEM complies with the specifications for the level 2 DTED format.
Quick turnaround: product covering approx. 500,000 km² ready in 3 months.
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An unlimited source of ground control points
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Reference3D orthoimages provide ground control points accurate enough to ensure GPS compatibility: 16 m CE90 or 10 m RMS.
They can be used to orthorectify imagery from most Earth observation satellites—e.g. SPOT, FORMOSAT-2, KOMPSAT-2, QuickBird, IKONOS, Envisat—when positional data are not available.
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Perfect data consistency
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Reference3D provides finely detailed information and close registration of data layers for:
- rigorous matching of map data, for example in the oil industry
- building onboard databases for UAVs, missiles and aircraft, and for mission planning, well suited to defence ministries and armament manufacturers
- compiling or updating maps
- checking existing databases
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