Ground Control Point Survey
Ground Control Points (GCPs) are required to accurately relate aerial image and LiDAR features to their corresponding 'real-world' position. The most challenging part of the GCP survey is to identify suitable ground features and to apply the most appropriate GPS survey method to achieve the accuracy required.
Geocomp International can provide the data acquisition from the planning stage to the management of the acquisition and with the successful data collection in the field. We directly manage and supervise to collect data ourselves, or we can also provide project nanagement services to team up with your resources to manage large projects.
We provide rapid-respose ground control survey anywhere in the world at the customer's desired level of accuracy, and in a timely, cost-effective manner. We can also save you the cost of sending such a crew, if a suitable GCP can be supplied from our archive data and falls within our GCP coverage. We also provide a GCP report sheet to enable each surveyed feature to be identified on the associated aerial image or point cloud.
With over 15 years of GPS surveying experience, we have undertaken many GCP surveys in different parts of the world; including Africa, Middle East, Asia, Australia and New Zealand.
Ground Control Point Specification
We can provide GCP data with metre to sub-decimetre level of accuracy, tailored to the requirements of your project. We also supply the GCP data with viewable metadata indicating date of collection and positional quality. Also supplied is supporting data that includes a control point sketch and photographs of the control point taken during collection.
The following are our regular GCP surveying specifications.
For satellite imagery with a spatial resolution of 1 metre and above, and +/- 1 metre horizontal and vertical accuracy requirements.
For imagery with a spatial resolution of 0.25 metre and above, and +/- 0.5 metre horizontal and +/- 1 metre vertical accuracy requirements.
For high resolution aerial imagery with an spatial resolution of 3cm to 20cm and one pixel accuracy requirement.
GPS Technology Used:
Virtual Reference Station and CORS
Single Base Real Time Kinematic Survey
Oministar Real Time Positioning
Static & Fast Static
Precise Point Position (PPP)
Trimble Net R5
CHC GNSS RTK
Ground Control Point Applications
spatial resolution of commercially available satellite imagery is improving rapidly, and the majority of satellite imagery available today requires ground truth or ground reference data to create accurate maps. Orthorectification without proper GCPs are inherently inaccurate.
Aerial Photography data acquisition and airborne IMU/GPS positioning technology is improving rapidly along with the availabiliy of GPS, GNSS and other satellite positioning technologies within the market. The requirement of GCPs for aerial photography projects is still essential for accurate mapping projects.
Geocomp International can provide both pre-marking and post-marking GCPs for all aerial photography projects, wherever it's needed in the world.
Airborne Laser Scanning
Airborne Laser Scanning requires a different type of ground control for the validation of horizontal and vertical accuracy of the point cloud data. The survey accuracy for LiDAR Validation GCP vary from +/- 25-50cm horiztonally and +/- 5cm to 15cm vertically, depending on the projects accuracy requirement.