Global Positioning Systems (GPS) Surveys

Global Positioning Systems (GPS) Surveys

Surveying and mapping was one of the first commercial adaptations of GPS, as it provides a latitude and longitude position directly without the need to measure angles and distances between points.  There are three methods of GPS measurement that are typically utilized by surveyors including:

Static GPS Baseline. Static GPS is used for determining accurate coordinates for survey points by simultaneously recording GPS observations over a base point and a second point for at least 20 minutes.   The GPS is typically done a second time after a period of time has elapsed and the satellite configuration above has had a chance to transmit a second set of data.  The data is then processed in the office to provide coordinates with an accuracy of better than 5mm depending on the duration of the observations and satellite availability at the time of the measurements.

Real Time Kinematic (RTK) Observations. This method of GPS measurements includes setting up a GPS Base Receiver over a known point – the Base Station – and another receiver moves between positions – the Rover Station. The position of the Rover can be computed and stored within a few seconds, using a radio link to provide a coordinate correction from the Base Station. This method gives similar accuracy to baseline measurements within 10km of the base station.

Continuously Operating Reference Stations (CORS). This method includes a survey quality GPS receiver that is permanently installed in a location as a starting point for any GPS measurements in the area. Surveyors’ GPS receivers can then collect field data and combine it with the CORS data to calculate positions. GPS data is typically processed using the National Geodetic Survey Online Positioning User Service processing system to deliver GPS data solutions over the internet within 24 hours.  Local CORS networks are also used to provide instant positions similar to the RTK method by using a mobile phone data link to provide a coordinate correction to the surveyor.

 

Past Projects:

  • Silver Springs Units 2 and 3, El Dorado County, CA
  • Mule Creek State Prison, Ione, CA
  • West False River Levee Monitoring, Contra Costa County, CA
  • Silver Springs Parkway Extension Project, El Dorado County, CA
  • Liberty ALTA Survey, City of West Sacramento, Yolo County, CA
  • Northstar Highlands II – Large Lot Final Map Phase 1

 

Learn more about Global Positioning Systems (GPS) Surveys at

Online Positioning User Service (OPUS)