Relative height measurement for railway slope using HDTV system

Japanese island is covered mountains nearly 80%, then railways and highways are run through the mountainous area. Recently those mountains are running to wild, therefore railway or highway companies are being stand in need of maintenance strictly. Relative heights for railway slope are measured and video maps are produced using High Definition TeleVision system. The HDTV system is a system designed to collect highly definitioned and stabilized images with GPS data turned out by HDTV camera. The 237.2 km along the railway are photographed. And relative height of 530 points are measured. Then measurement accuracy was 0.9 m average. The HDTV system is good for such as long target, sporadic points measurement and rough accuracy request.