Ground Control Points

KPGeo's Ground Control Points offer covers the planning, measurement and documentation of ground control points (GCPs), the surveyed reference points used when producing orthophotos and maps from aerial, UAV or satellite imagery. Working with its own resources and a global network of partners, KPGeo states that it has performed GCP surveys at more than five hundred project locations in Africa, Asia, Australia, Europe and South America.

Measurements are made with Trimble GNSS receivers that support multiple satellite constellations and correction sources, built on the Trimble Maxwell 6 chip with 220 channels. KPGeo has used static survey, Real-time Kinematic (RTK) and OmniSTAR correction methods. Each survey is delivered with a report on the accuracy and survey methods used, field sketches, in-situ photo documentation, and coordinates converted into a wide range of horizontal and vertical reference systems. Before delivery, every point goes through quality control that includes checking that it can be identified on satellite imagery, and the deliverables also include image chips showing each point's location and the original survey data in T02 and RINEX format.

Points measured on earlier projects are listed in the KPGeo Geoportal, a web map where users outline an area of interest to see each point's rounded coordinates, measurement accuracy and capture date, open its photos and sketches, and export the list to CSV or KML. Exact coordinates and original data are ordered from KPGeo's sales team.

In a published case study, KPGeo supplied GCPs for more than 400 airport locations for DigitalGlobe's 3D airport mapping, terrain and obstacle database programme, capturing 8 to 10 control points per airport at a minimum accuracy of 0.7 m horizontal (CE90) and 1.25 m vertical (LE90).