2 ms·This is more or less how airport glide slope indicators work.by cwillu 2y agoThis is more or less how airport glide slope indicators work.knodi123 2y agohttps://en.wikipedia.org/wiki/Precision_approach_path_indicator https://en.wikipedia.org/wiki/Precision_approach_path_indica...moi2388 2y agoWell that was an interesting read regarding PAPI and VASI :)