Recently, digital photogrammetric cameras have been developed, including the commercial systems ADS40 (LH Systems), DMC (Z7I Imaging) and the Japanese TLS (Starlabo), as well as HSRC of DLR. A crucial factor for the success of the new digital sensors is the development of associated software with high-quality performance that fits the characteristics of each sensor. For example for ADS40, matching can make simultaneous use of up to 7 images for each strip, and the known interior and exterior orientation of each line can be exploited to enforce geometric constraints. The datasets that were processed come from two regions, with different landscape and density of houses and trees. The dataset of Waldkirch (CH) covers a rural/suburban area (image scale is 1:30000 and pixel footprint 0.2 m) and the dataset of Chofu (JP) an urban one (image scale is 1:25000 and pixel footprint 0.17 m).
Description of ADS40
ADS40 incorporates latest GPS and INS technology (Applanix) for sensor orientation and new developments in sensor technology, optics, electronics and data transfer and storage. The ADS40 data used come from a camera with seven parallel sensor lines in the focal plane of a single lens system – three panchromatic (forward, nadir, backward), red, green, and blue lines placed next to each other and one infrared. The focal plane has space for two additional lines, but these are not currently used. Each panchromatic channel consists of two lines, each with 12000 pixels, staggered (shifted with respect to each other) by 0.5 pixels. In the test data used here, only one staggered line for each panchromatic channel was used. The viewing angles and characteristics of the sensor are shown in Table 1. Additional information on the ADS40 is given in Reulke et al. (2000), Sandau et al. (2000) and Tempelmann et al. (2000).
Table 1. ADS40 characteristics.
| Focal length |
62.5 mm |
| Pixel size |
6.5 mm |
| PAN |
2*12000 pixels |
| RGB – NIR |
12000 pixels |
| Forward to nadir stereo angle |
28.3° deg |
| Backward to nadir stereo angle |
-14.1° deg |
| Near infrared to nadir stereo angle |
-2.05° deg |
| RGB to nadir stereo angle |
15.9° deg |
| No. of bits from the ADC |
14 |
Ground Processing
Apart from the imagery, GPS position and IMU data are recorded during the flight and written to the mass memory system (MMS). GPS/IMU data from the Applanix system are post processed to provide orientation for each image line. To compensate remaining errors (e.g. errors in the GPS/IMU post processing, IMU misalignment, calibration errors), a bundle adjustment (aerial triangulation) is applied with a number of GCPs and tie points. Tie points are matched in images rectified on a plane by using the raw GPS/IMU data, and their coordinates are transformed to the raw images before entering the bundle adjustment. The results of the bundle are used for a more accurate rectification. The rectification is needed for stereo viewing, DSM/DTM measurement, mapping etc. within Socet Set. The raw images are referred to as Level 0 images and the rectified ones as Level 1.