I remember that a member here lost his brother who was a crop duster around the California Delta. The law for the allowable height of unlighted/unmarked poles (not sure what the poles were for - maybe meteorological monitoring) was 200 feet and someone built some right up to the limit with no lights or markings. There was low visibility and the member's brother died in the crash. The State changed the law after that, but it was tragically too late.