The three-hours GPS observation by Trimble 4000 SD receivers was repeated at five stations in central Japan every day during four weeks from February 25, 1990. Data obtained from five satellites could achieve good results 2-4 times better than previous works with four satellites. The standard deviations of baseline lengths, namely the day-to-day repeatabilities, by the the triple difference technique were 0.11-0.48ppm for all of ten baselines ranging from 22km to 172km. However, those of eight baselines longer than 40km show less than 0.2ppm. The double difference technique applied to the shortest baseline (Nagoya-Inuyama, 22km) data too. This could improve the standard deviation from 7mm (0.31ppm) to 4mm (0.17ppm). The GPS observation under five satellites utilization maintains the same precision precision as electro-optical distance measurements (EDM), even for a few tens-kilometer baseline.
