100 likes | 280 Views
BCLS 2009 AGM GPS FOR TRADITIONAL SURVEYING. Simplifying GPS Position Referencing On Day to Day Surveys. By: Keith Belsham, Technical Sales Representative Butler Survey Equipment 1-800-667-5944. Types of Professional GPS Used Working in a Local Coordinate System with
E N D
BCLS 2009 AGMGPS FOR TRADITIONAL SURVEYING Simplifying GPS Position Referencing On Day to Day Surveys By: Keith Belsham, Technical Sales Representative Butler 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
Types of Professional GPS Equipment Used • GNSS Rovers with reference station connection over the internet via cellular modem
Types of Professional GPS Equipment Used • Base & Rover with Radio Connection
Types of Professional GPS Equipment Used • Dual or Single Frequency Static GPS Receiver
Matching to Existing Control • 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
Matching to Existing Control RESECTION GPS LOCALIZATION
Georeferencing • 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)
Common Errors • 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