Method and apparatus for scanning a terrain surface

Abstract

A method and apparatus are disclosed for scanning a surface of an object, transversely to a direction of motion. A scanner is provided for flying over the object at a flight altitude and flight velocity, having a system focal length, a scanning element rotating at a rotation speed which scans a surface over a scanning angle and a detector row, arranged at right angles to the scanning direction. A detector row is provided with a plurality of equal size individual detectors, which are capable of generating fundamental object pixels of a size which depends upon the distance from the object up to a maximum scanning distance. A standard object pixel, of a size corresponding to a fundamental object pixel, is driven at the maximum scanning distance. For each scanning sweep, via a sampling process, a uniform grid is formed which is composed of standard object pixels of a size corresponding to a fundamental object pixel at the maximum scanning distance in several lines and without gaps and/or overlaps. Uniform grids of consecutive sweeps have no gaps and overlaps between each other. A sampling process is performed for forming a uniform grid, independent of an actual flight altitude, and an actual flight velocity for each scanning sweep. The system focal length and the rotational speed of the scanner are controlled as functions of an actual flight altitude and flight velocity so that uniform grids, of consecutive scanning sweeps, have no gaps and/or overlaps between each other.