2.8 Cameras for Remote Sensing

2.8 Cameras for Remote Sensing

Aerial survey cameras, multispectral cameras, panoramic cameras etc. are used for remote sensing.

Aerial survey cameras, sometimes called metric cameras are usually used on board aircraft or space craft for topographic mapping by taking stereo photographs with overlap. A typical aerial survey camera is RMK made by Carl Zeiss or RC series made by Leica company. Figure 2.8.1 shows the mechanics of the Zeiss RMK aerial survey camera.

Typical well known, examples of space cameras, are the Metric Camera on board the Space Shuttle by ESA, the Large Format Camera also on board the Space Shuttle by NASA, and the KFA 1000 on board COSMOS by Russia. Figure 2.8.2 shows the LFC system and its film size. Figure 2.8.3 shows a comparison of photographic coverage on the ground between LFC (173 km x 173 km) and KFA (75 km x 75 km).

As the metric camera is designed for very accurate measurement of topography, the following requirements in optics as well as geometry should be specified and fulfilled.

(1) Lens distortion should be minimal
(2) Lens resolution should be high and the image should be very sharp even in the corners
(3) Geometric relation between the frame and the optical axis should be established, which is usually achieved by fiducial marks or reseau marks
(4) Lens axes and film plane should be vertical to each other.
(5) Film flatness should be maintained by a vacuum pressure plate
(6) Focal length should be measured and calibrated accurately
(7) Successive photographs should be mode with high speed shutter and film winding system
(8) Forward Motion Compensation (FMC) to prevent the image motion of high speed moving objects during shutter time, should be used, particularly in the case of space cameras

Multispectral cameras with several separate film scenes in the visible and reflective IR, are mainly used for photo-interpretation of land surface covers.

Figure 2.8.4 shows a picture taken by the MKF-4, with 4 bands, on board the Russian Soyuz 22.

Panoramic cameras are used for reconnaissance surveys, surveillance of electric transmission lines, supplementary photography with thermal imagery, etc., because the field of view is so wide.