Photogrammetry and Laser Altimetry

Laser altimetry has, and is continuing to have a profound impact on photogrammetry. This paper discusses the interrelationship between the two fields, identifies problems, and suggests a common research agenda. Surface reconstruction is an important application in photogrammetry. DTMs, for example, are as much an end result as an intermediate step for orthophoto generation and for object recognition. The quality control is a central issue, regardless how the surface is obtained. The paper analyzes the effect of systematic errors of laser ranging systems on the reconstructed surface. To keep these effects as small as possible, rigorous calibration methods are necessary, including suitable test surfaces and proper error modeling. In a more complex setting, better results are achieved if laser ranging is combined with stereopsis. The combination of different surface measurements is a challenging fusion problem. At the sensor level, the systems, such as camera and laser, can be tightly integrated to the degree that the laser footprint is recorded by the camera. On the feature level, extracted features from imagery and laser ranging must be combined in a way that accounts for the different error models. Finally, on the symbolic level, a combined surface must explain the measurements resulting from the different sources.