Global Navigation Satellite Systems (GNSS), of which the US Global Positioning System (GPS) with satellites orbiting about 20200 km above the Earth is one constellation, can be used to provide position and time information anywhere on or near the Earth. An unobstructed view to at least four GNSS satellites is required to calculate a position (latitude, longitude, and elevation) and correct for any receiver clock error. Position changes of the GNSS antenna can then be found over time, both horizontally or vertically.
Earth and atmospheric science applications for the GPS system typically utilize a GPS reciever capable of millimeter-level precision. This high-precision capability is obtained by tracking multiple GPS satellite signals and by post-processing the GPS data along with other stations to provide a network wide position estimate. This post-processing of GPS data can eliminate many of the errors in order to achieve the millimeter level precision.
Permanently installed GPS stations have the advantage of monitoring changes in the position of the station over the long-term. GPS data from permanent stations can be downloaded before, during, and after geophysical events such as earthquakes and volcanic eruptions, which provide scientists with a tool to better understand Earth and atmospheric processes. Mobile GPS units (campaign GPS) have the advantage of being able to make many short-term measurements over many different locations at a much lower cost and without the need for elaborate power and data communications systems.
GNSS Receivers and GNSS Antennae (for GPS, GLONASS, SBAS, Galileo, Beidou/Compass, QZSS) collect can full GNSS data which, after processing, can also be used to measure millimeter-level surface motion measurements at specific points over a period of time; the datasets include temporary, episodic campaign surveys and permanent installations.
Last modified: Friday, 01-Apr-2016 22:51:21 UTC