Each year fog at airports renders some landing operations either difficult or impossible. In such instances, visibility is the most important information for the pilot of a landing aircraft. Visibility may be constant, decreasing, or increasing with respect to the altitude; however, it is not possible to distinguish this with existing airport sensors. This paper describes a new technique for measuring slant visual range that makes use of a slant scanning device, an eye-safe laser radar.
This device has been tested by the German Meteorological Service in Quickborn, Germany, over a period of one year. A comparison with commercial visibility sensors shows that it is possible to measure visibilities with the slant-looking laser radar in the range from 50 m up to 2000 m and to even distinguish inhomogenities like ground fog. Statistics of the Quickborn measurements show that the atmosphere in that region is not homogeneous in 38% of fog situations, which would at the present lead to a restriction of the air traffic.
The first installation of this instrument at the Hamburg airport is described.