How do you know it is true?
When Accuracy Matters
CompassData provides crucial Quality Control for LiDAR data. While independently derived Ground Control Points are an important element in LiDAR quality evaluation, sensor calibration can be a complicated procedure.
BENEFITS of CompassData Solution
- Accurate and repeatable accuracy for Ground-Truthed GeoData
- Standardized production flows increasing efficiency
- Customized solutions
FEATURES of CompassData Solution
- Standardized Delivery of a GCP from anywhere in the world
- Geodetic accuracy (worldwide)
- High contrast (greyscale)
- Sharp geometry (90-degree corner)
- Permanent (concrete)
REMOTELY SENSED GCP
TOO REMOTE OR TOO DANGEROUS FOR FIELD DATA COLLECTION
Remotely Sensed GCP (RSGCP™) is offered by CompassData. Remotely Sensed Ground Control Point provides a control for those areas that are too remote or too dangerous for field data collection crews to go in person or where on-ground GNSS surveys are not possible.
Image of a Ground Control Point in which the 3-D ground control data was acquired via TerraSAR-X satellite.
To complement CompassData’s archive of terrestrial GNSS collected GCPs, we are working with Infoterra GmbH, as an authorized re-seller, using the new Synthetic Aperture Radar (SAR) sensor technology, combined with an extremely precise on-orbit platform.
Although GCPs collected by terrestrial means typically offer higher accuracies, this spaceborne approach is a significant milestone in control.
This is possible through:
- A very high degree of orbital accuracy of the TerraSAR-X satellite, (residing in the centimeter range)
- Very precise radar beam tracing
- Extremely high-resolution capabilities of the satellite and the resulting high geolocation accuracy of the SAR imagery (<1m in Range and Azimuth for two collection modes)
The sensor is highly suited for collecting precise and accurate 3D ground information regardless of whether or daylight conditions. Infoterra follows the accuracy standards established by CompassData Inc. to provide data collection in two standard offerings:
- RS-1 Precision: Based on 3-4 High-Resolution SpotLight scenes, 5 GCPs at <=1m accuracy can be generated within an area of 20 km2
- RS-2 Precision: Based on 2 StripMap scenes, 8 GCPs at <=3m accuracy can be generated within an area of 1,000 km2
The Remotely-Sensed GCP data are delivered to the customer in the same fashion as CompassData terrestrial GNSS control points, including:
- An Image Chip corresponding to the SAR Image Chip for the control point
- Metadata file in CSV format
- SHAPE file for the Area of Interest
- KML file for viewing in Google Earth™
- An Accuracy Report and a Site Sketch providing additional details regarding the RSGCPs
TERRASAR-X ORBITAL ACCURACY AND PRECISE RADAR METRICS ENABLE SPACE-BASED GROUND CONTROL POINT COLLECTION WORLD-WIDE
Station Diagram of Remotely Sensed Ground Control Point, included in the CompassData standard deliverable
CompassData has tested Remotely Sensed Ground Control Points to verify the accuracy.
Our RSGCPs provide a guaranteed accuracy of less than or equal to 1 m. The accuracy of 3D ground control points retrieved from TerraSAR-X SpotLight and StripMap images have been evaluated by validating the RSGCP coordinates against Differential GNSS control points and/or a highly accurate LiDAR DEM on varied test sites, all situated in challenging terrain. Nevertheless, as RSGCP accuracy strongly depends on terrain conditions and identifiable points, feasibility studies of each Area of Interest are performed.