Heavy & Highway GNSS & Total Stations Basics

1. Heavy & HighwayGNSS & Total Stations Basics

2. What is GNSS? • Global Navigation Satellite System • used by receivers to determine location anywhere on earth • Satellite Systems include • GPS (USA) • GLONASS (Russia) • Galileo (Europe, currently not operational)

3. GPS Receivers • Three Types of GPS Receivers • Navigation/Recreational (Autonomous) • 10’-50’ (3m-15m) H, V? • Location GPS (Differential GPS - dGPS) • 0.5’-10’ (0.1m-3m) H, 2-3x more in V • Precision GPS (Real-Time Kinematic -RTK) • 0.1’ (30mm) or better, 3D! • Precision GNSS for Heavy Highway

4. Is it accurate? - YES!! Trimble dGPS: 0.1–3 m RTK: 1–2 cm Standalone GPS: 5–10 m

5. How Does it Work? • Rover (s): • - Machine • Range Pole • Site Vehicle Base Station

6. How Does GNSS Work • The base and rovers track or receive the same satellite signals AT THE SAME TIME. • The base station sends its position & observations via radio to the rover • Base station data and rover data are processed together in rover receiver to produce 3D vector • Base station position + vector = rover position • Result: ALL POSITIONS @ THE ROVER(S) ARE RELATIVE TO BASE POSITION

7. What Do You Need? • Precision GNSS uses 2 receivers • Base Receiver • Rover Receiver • In addition you need • GPS Antennas • Radios • Radio Antennas

8. What is a Modular GNSS Receiver? • Separation of components • Allows mix and match of GPS & Radio antennas • Optimized use • Permanent, semi permanent, • vehicle or marine vessel setups • Security • Accessible, secure, and environmentally protected

9. What is a Smart GNSS Antenna? • Fully integrated GNSS receiver • Optimized for pole mounted rover solution • A rapid setup, high mobility base station • Receiver incorporates • GNSS receiver • GNSS antenna • Radio and radio antenna • Removable battery • Bluetooth for cable free operation • Quick, easy setup and tear down for small sites and rapid mobilization

10. GPS Coordinates NEE Tying it all together… • GPS Site Calibration • What is a site calibration? • Defines the relationship between GPS Coordinates and local northing, easting, and elevation • Why is a site calibration required? • Allows multiple GPS-based rover systems to work in your local site coordinate system • What is needed for site calibration • Onsite control based on local coordinates

11. What can go wrong? • Bad Base Location • Bad base observations, bad rover corrections • Setup GPS base station antenna with 360° view of the sky. If limited try to set up with clear visibility to the equator. • Multipath • Avoid sources of multipath (deflection of the GPS signal) • Base-Rover Radio Link • Radio “Line-of-sight” • Other Radio Interference • PDOP • Position Dilution Of Precision (SV Geometry) • Human Error • Bad base position or calibration

12. SPS Total Stations • Total Stations are used for the highest accuracy work • Heavily used on highways, railways, bridge, and tunnel projects • Many contractors need both total stations and GPS • When a contractor buys a total station they should strongly consider Trimble SPS universal instruments • SPSx20 • SPSx30 • Total Stations require more accurate control • Total Stations get less accurate over distance

13. Total Station vs GPS

14. How Does a Total Station Work? • Measures angles and distances • By measuring known points, a TS calculates it´s position relative to known points and coordinate system • Known points should be high order control • In Robotic mode, the TS measures the position of the rover target and reports the position information via radio link to the rover • SCS900/GCS900 compares the position to design information calculating Cut/Fill

15. TS Setup – Arbitrary Location • Pros • Freedom of where to place the instrument • Easy to set up the legs • No instrument height measurement • Cons • Must visit two known points to establish the position – Takes extra time • Should always have another point not used in the setup for checking the setup • This method is used most often in construction

16. TS Setup – Known Control Point • Pros • Only need a backsight to one known point to establish the position • Quicker setup as you only have to visit one other point • Cons • Restricted as to where to place the instrument • Location may be harder to set up the legs • Must measure instrument height • Should always have another point not used in the setup for checking the setup.

17. CP2 CP1 TS Arbitrary Setup BAD SETUP! Resection angle <30 degrees

18. CP2 CP1 TS Arbitrary Setup GOOD SETUP! Resection angle 30 – 150 degrees

19. What can go wrong? • TS out of calibration • Perform all user capable calibrations on regular basis • Bad setup • HA out of tolerance • We are chasing high accuracy. • Do not accept a setup if out of tolerance, even if the point deviations are acceptable • Bad TS Location • Setup TS with clear visibility to the rover and limited potential obstructions • Do not place TS close to vibratory compacter operation • Weak tripod • Use a heavy duty tripod with sturdy top plate • Do not use aluminum

20. Questions?