Continuous Global Positioning System (CGPS) Stations
Measurements of elevations, aquifer-system compaction, and water levels are used to improve our understanding of the processes responsible for land-surface elevation changes. Elevation or elevation-change measurements are fundamental to monitoring land subsidence, and have been measured by using continuous GPS (CGPS) measurements and campaign global positioning system (GPS) surveying.
A CGPS station continuously measures the three-dimensional (3D) position of a point on, or more specifically, near the earth's surface. There are more than 1,000 Continuous Global Positioning System Stations operating in Western North America, and hundreds of them in California alone; many of them are managed by the NOTA Network Monitoring/UNAVCO and by Scripps Orbit and Permanent Arrary Center (SOPAC), but other groups such as Caltrans, also operate some of them as part of their Central Valley Spatial Reference Network. They generally have been constructed to monitor motions caused by plate tectonics, but are widely used for other applications, including subsidence monitoring.
These GPS stations generally collect position information every 15 seconds which are then processed to produce a daily position. These daily positions are then concatenated to produce a daily time series, which allow us to track the 3D position of the station.
Below are data or web applications associated with this project.
Central Valley: Drought Indicators
During the recent droughts of 2007-2010 and 2012-2017, groundwater pumping has increased from the combined effects of the drought and land-use changes, re-initiating land subsidence. In order to document historical subsidence and monitor continued changes, the USGS has gathered and interpreted data from a variety of sources.
Measurements of elevations, aquifer-system compaction, and water levels are used to improve our understanding of the processes responsible for land-surface elevation changes. Elevation or elevation-change measurements are fundamental to monitoring land subsidence, and have been measured by using continuous GPS (CGPS) measurements and campaign global positioning system (GPS) surveying.
A CGPS station continuously measures the three-dimensional (3D) position of a point on, or more specifically, near the earth's surface. There are more than 1,000 Continuous Global Positioning System Stations operating in Western North America, and hundreds of them in California alone; many of them are managed by the NOTA Network Monitoring/UNAVCO and by Scripps Orbit and Permanent Arrary Center (SOPAC), but other groups such as Caltrans, also operate some of them as part of their Central Valley Spatial Reference Network. They generally have been constructed to monitor motions caused by plate tectonics, but are widely used for other applications, including subsidence monitoring.
These GPS stations generally collect position information every 15 seconds which are then processed to produce a daily position. These daily positions are then concatenated to produce a daily time series, which allow us to track the 3D position of the station.
Below are data or web applications associated with this project.
Central Valley: Drought Indicators
During the recent droughts of 2007-2010 and 2012-2017, groundwater pumping has increased from the combined effects of the drought and land-use changes, re-initiating land subsidence. In order to document historical subsidence and monitor continued changes, the USGS has gathered and interpreted data from a variety of sources.