New technology continues to offer the aerial mapping community a wide variety of digital camera choices in addition to the traditional film cameras. While the U.S. Geological Survey (USGS) continues to calibrate film cameras, capability to calibrate digital cameras is being developed.

Digital systems are being studied to further develop digital camera calibration capabilities. To date, investigations have focused primarily on the ability to characterize and calibrate geometric and spatial aspects of digital aerial sensors. The USGS is also beginning to develop the capabilities for characterizing the radiometric performance of sensors, both in the laboratory and in the field.

A Digital Camera Calibration lab is in place at the USGS Earth Resources Observation and Science (EROS) Center, housing a 12’W x 10’H x 8’D “calibration cage,” containing 207 mapped reflective points on 3 planes, and an 8’W x 6’H tautline board containing 9 horizontal lines, 9 vertical lines, and 64 points.

Research on the geometric calibration of small and medium digital cameras is currently underway using the cage. Using the cage method, a camera is mounted on an adjustable tripod and 9 exposures are taken from 9 different exposure stations with the differing angles pointing toward the center of the cage. The tautline method takes landscape and portrait images at each of 6 exposure positions. The resulting digital images from either method are then measured and the data is entered into a software program that calculates calibration results.

The lab also contains a resolution target (ISO 12233). Software and procedures are being prepared to analyze the Modulation Transfer Function (MTF) of camera systems.

The USGS EROS also maintains ranges used in characterizing aerial imagery from a camera in flight (in situ). The 320 acres that compose the EROS campus have been used for numerous aerial campaigns and, if needed, can be used for special projects. A control point range within the borders of the city of Sioux Falls, S.Dak., has also been established with strong support and cooperation from the city’s Geographic Information System (GIS) Department. This site was designed to aid in characterizing a wide variety of high-resolution remote sensing products, from 6-inch (or smaller) aerial imagery to 1-meter, 15+ km swath-width satellite imagery. The EROS and Sioux Falls ranges are supported by nearby National Geodetic Survey Continuously Operated Reference Stations (CORS) providing data for post-processing of Global Positioning System (GPS) data.

For more information about these resources and more available from the Remote Sensing Technologies Project, or to schedule your digital camera for calibration, please contact Greg Stensaas at 605-594-2569 (stensaas@usgs.gov) or Mike Benson at 605-594-6938 (benson@usgs.gov).

(Note: Once your digital camera system has been scheduled, please review Instructions for Sending Camera Systems to the USGS EROS Center.)