GCP Collection

There has been a dramatic increase in the practical use of mapping data and imagery, in applications barely envisioned a decade ago. Automotive GPS navigation systems, web-based interactive mapping displays and direction queries, online imagery and address query have all driven the development and inclusion of imagery and maps into our everyday lives.

In order to be of any use spatially, Airborne and Spaceborne imagery must be referenced to the real world. By recording precise coordinates of photo-identifiable locations within an image, those coordinates form the basis for remapping that image through robust software into a usable, accurate map image, usable in a variety of applications.

Without ground control, accuracies for spaceborne images are typically 20-50 meters based on onboard position and attitude sensors and known orbital parameters. Once ground control has been applied, those accuracies increase to 1-2 meters or better. In general terms, with aerial photography there is no initial inherent accuracy, as the normal data associated with an aerial image at capture is a simple X, Y, Z coordinate set for the approximate photo center.

Through the use of ground control and sophisticated terrain modeling techniques, aerial images can be generated into orthophoto maps with sub-foot relative accuracies and absolute accuracies of under 2 feet.

Contrary to popular belief, higher quality aerial or satellite imagery will not replace the need for ground control. In fact, ground control point collection becomes increasingly more important as image quality improves and user expectations increase. Fortunately, collecting ground control is now a much faster, more accurate, and cost-effective process thanks to the use of GPS.

For more information or to place an order, please call Kate Schlatter at (303) 627-4058 or send an email to Solutions@CompassDataInc.com.