Image overlap
When image overlap or short overlap in which is photogrammetry , the common image region designated on the adjacent two measurement images is illustrated. An exact measurement of the terrain and easily recognizable image points can be carried out in the coverage area.
During a measurement flight for the production of the map, the terrain is flown over in a loop (see adjacent picture). The row cameras used for this, mounted in the aircraft floor, have devices for automatic overlap control, which is carried out either with a downward-pointing navigation telescope or by means of GPS . The standard is a longitudinal overlap of 60 percent (in the direction of the flight lanes) and a transverse overlap of around 20%. A sufficient, but not too large, longitudinal overlap is a prerequisite for the evaluation by means of stereophotogrammetry , whereas the transverse overlap is a prerequisite for the complete coverage of the project area.
In the overlap area of the measurement images, the points to be measured can be localized on two images and their position can be determined by means of geometric cutting processes (analogous to the forward cut ). The evaluation of such image pairs takes place u. a. using a stereo comparator or autograph. With the so-called block adjustment , the sections are not calculated in pairs, but in a larger image group.
In addition to image flights , sufficient image coverage is also necessary for terrestrial photogrammetry ( earth image measurement ), for example for photographic recordings for architecture or accident photogrammetry .
Literature:
- K. Kraus, W. Schneider: Remote sensing Volume 1, Dümmler-Verlag Bonn 1988.