Tidal Action on Land Tidal Action on Land LCruiser (Civil/Environmental) (OP) 7 Sep 06 22:35 Does anyone have any quantitative representations of tidal influence on land with respect to GPS? RE: Tidal Action on Land IRstuff (Aerospace) 8 Sep 06 00:58 Which GPS? The typical GPS receiver is not able to discern any sort of ground movement. High-end real-time or post-processed differential GPS with millimeter accuracies are being used to measure earth movement around earthquake faults.see also:http://www.astro.oma.be/ICET/bim/text/WG6GPS.htmhttp://www.astro.oma.be/ICET/bim/text/WG6frw.htm TTFN RE: Tidal Action on Land LCruiser (Civil/Environmental) (OP) 8 Sep 06 10:05 They measure relative movement. Earth's crust moves just like the oceans, but only on a smaller scale - related to the density difference between water and rock. That's why it's important to use differential GPS when surveying. A base station is set up on a known point and the difference between what the point is known as and is being reported is subtracted from the roving unit's readings.