Custom Ground Control Points

CompassData's custom Ground Control Point (GCP) service sends survey teams to collect new, survey-grade control points at a buyer's project site anywhere in the world. It is the alternative to CompassData's GCP archive when no suitable archived point exists, site conditions have changed or tighter accuracy is required. Without ground control, imagery, orthomosaics and 3D models can drift from their true position by metres; GCPs tie satellite, aerial, drone, LiDAR and mobile-mapping data to real-world coordinates for orthorectification, sensor alignment and independent accuracy validation.

Surveyors use dual-frequency GPS/GNSS receivers and total stations, choosing static, rapid-static or RTK methods to suit the site. Every new point is post-processed with precise ephemeris corrections, cross-checked against control networks such as CORS and national geodetic databases, and quality-controlled under ISO 9001:2015-certified workflows. CompassData states that delivered accuracy ranges from sub-metre to centimetre level, depending on the project's requirements, geodetic processing methods and applicable industry standards. Points are planned around photo-identifiable, permanent, flat features for the target accuracy, coordinate system and spatial reference, with photogrammetric panel targets placed where natural features are insufficient. CompassData gives a typical survey timeline of 2-4 weeks.

Deliverables include coordinate files (latitude, longitude, elevation) in client-specified formats, Esri shapefiles and Google Earth KML, photos of each point from the four cardinal directions plus a close-up, station diagrams, geo-referenced image chips showing each point in the source imagery, and post-processed reports of horizontal and vertical accuracy. For restricted, remote or hazardous areas, CompassData also offers Remotely Sensed GCPs (RSGCP). Each survey is quoted per project.