Radiometric evaluation of digital aerial cameras

Advanced radiometric properties of new digital photogrammetric sensors will open new applications for photogrammetric sensors. In order to learn to use the systems properly and to find out the limitations of the systems, sensor testing in operational conditions is essential. Radiometric properties of image data sets collected by Intergraph DMC, Leica ADS40, Vexcel UltraCamD and a medium format sensor Emerge DSS have been evaluated using the calibrated 8-step gray scale of the Finnish Geodetic Institute. In this article, exemplary results of various sensors are given. Results showed that saturation started at reflectance values of 27% to 66%, depending on the data sets. Central factors affecting the radiometric results were the sensor parameters during the image collection and the radiometric post-processing options. The presented results should not be used to compare various sensors but they are intended to demonstrate the many factors affecting the radiometric properties. However, results also show that in ideal conditions and with proper parameters the expectations set for the digital censors are fulfilled. Radiometric calibration and testing in field is crucial to utilize the advanced radiometric characteristics of the digital sensors to an optimum effect.