Simplifying GPS Position Referencing On Day to Day Surveys Keith Belsham, Technical Sales Representative ler Survey Equipment 00-667-5944
Simplifying GPS Position ReferencingOn Day to Day Surveys
By: Keith Belsham, Technical Sales RepresentativeButler Survey Equipment 1-800-667-5944
- Types of Professional GPS Used
- Working in a Local Coordinate System with Real-Time GPS Receivers
- Geo-referencing a Survey
- Common Errors with GPS
GNSS Rovers with reference station connection over the internet via cellular modem
Base & Rover with Radio Connection
Dual or Single Frequency Static GPS Receiver
Want to work in a local ground based coordinate system (5000,5000,100)
Same principle as a resection or Helmert’s or Least Square adjustment with a total station, with line of sight being to satellites
By measuring local points with the GPS you can shift, rotate & scale to match your coordinates
RESECTION GPS LOCALIZATION
Most systems will store a GPS position in the background that you can later reference to
Keep in mind what you are referencing your GPS to (ie what corrections is your Rover receiving)
May need to use a service like the Federal Governments Precise Point Positioning to verify base positions in remote areas (http://www.geod.nrcan.gc.ca/online_data_e.php)
No correction data being received & accuracy warnings are ignored
GPS base position isn’t corrected
When localizing, the residuals aren’t checked
Modern GPS systems are designed to make the transition from total station surveying to GPS seamless
We now have more satellites making GPS work better than ever◦ Glonass constellation from Russia◦ Compass constellation coming from China◦ Galileo constellation coming from Europe◦ Extra frequency coming on US GPS satellites