Principal platforms and their sensors for land evaluation

• Low-flying aircraft with photographic cameras

This platform has rich history (American Society of Photogrammetry, 1983). Well-developed techniques for photointerpretation for a wide variety of purposes (vegetation, landforms, soil survey, geology, infrastructure...).
Scale of original photography on the order of 1:6 000 to 1:60 000, depends on flying height and focal length of camera.Excellent resolution, limited only by the sensitivity and resolution of the film.Usual procedure: manual interpretation and drawing of polygons, lines or points, followed by digitizing (or scanning of the hand-drawn lines) for use in the GIS. Rectification and gereferencing can come before (orthophotos) or after interpretation.Can be scanned and converted in digital images with any desired radiometric (bits per pixel) and spatial (pixels per inch of photograph) resolution, then processed like satellite data.

• Low-flying aircraft with passive electromagnetic sensors

Same as above, but using charge-coupled diodes (CCDs) or digital cameras. Products go
directly to the image processing system without scanning, then are