Background
Topo Photo, Inc., founded in 1987, provides services for the development of in situ calibration methods for aerial cameras and associated sensors. It is the intention of Topo Photo, Inc. to be involved with measurement, calibration and development of the metric character of airborne sensors, leading to improved practical applications. Primary sensors are film-based and digital aerial cameras. Extensions to added sensors of the types IMU and LIDAR are considered. The development of UAS to achieve high geospatial accuracies is currently underway.
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Dr. Merchant of Topo Photo, Inc. has been involved with airborne calibration of film-based mapping cameras since 1968 when Zeiss RMK AR camera was calibrated by using photography taken over Mt. Graham and Casa Grande, Arizona. this experiment reported the substantial differences between calibration results obtained by in situ and by laboratory methods.
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Mt. Graham, Arizona (Altitude Difference, Peak to Valley>8,000 Feet)
Note that the altitude differences between high and low targets and the flight of the aircraft at 14,000 feet was still inadequate to sharply separate focal length from flight height parameters in the calibration adjustment computation.
As GPS became useful for measurement of the camera's exposure station, airborne methods of calibration and compilation became more important. an early example of airborne calibration with GPS control was accomplished by Capt. Lapine, NOAA, working with a Wild RC-10 camera in the NOAA Citation aircraft. Results, as reported in his PhD dissertation (OSU, 1990), clearly demonstrated the virtue of the airborne method.
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Subsequently, Topo Photo, Inc. worked to develop and demonstrate in situ methods of calibration for both film-based and digital cameras. One example is the calibration of the Zeiss RMK-II 140 camera by using photography over a developed crossroad range. Development of the range, flight patterns, and data reductions leading to an efficient process of airborne calibration are continuing.
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