1. Heavy & Highway GNSS & Total Stations Basics

2. Global Navigation Satellite System
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. 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
Depending on the application, there are three (3) different types or “grades” of GPS receivers:
Navigation or Recreational:
These receivers are your typical “fishing/hunting” type receivers

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

5. How Does it Work? Rover (s): - Machine Range Pole Site Vehicle
Base Station
- The Base and Rover (s) receivers track or receive the same satellite signals AT THE SAME TIME.
- The Base Station sends it’s 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 THE ROVER (S) ARE RELATIVE TO BASE POSITION

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 THE ROVER(S) ARE RELATIVE TO BASE POSITION
How dGPS works:
Base Station located on a known point
Receiver computes difference between the SV measurement and the expected measurement and broadcasts the correction to a rover receiver via radio
How do we have an expected measurement?
Base Station Location Known
SV Location Known
Distance to SV therefore known

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

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
Describe need for GPS ant, receiver, and radio at both base and rover before modular / smart

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. NEE Tying it all together… GPS Site Calibration GPS Coordinates
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
GPS
Coordinates
NEE

11. What can go wrong? Bad Base Location Multipath Base-Rover Radio Link
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
Change south to accommodate both north / south hemisphere
GNSS applies to multipath, pdop

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
Talk about difference between x20 and x30
What kind of accuracy vs GPS?
TS requires better control
TS get less accurate over distance

13. Total Station vs GPS Total Station GPS Ruggedness Less Rugged
(moving parts & user maintenance)
Water and dust resistant
Rugged
(no moving parts)
Water & Dust proof
Range
700m Robotic
350m Grade Control
Typical 1-3miles / 2-5km
Accuracy
0.01ft / 3mm
0.1ft / 30mm
Setup
Quick daily setup and use
Initial infrastructure requirement
Line of Sight
Line of sight to instrument
Line of sight to sky
Ruggedness of solution (TS not fully water proof, can’t drop it, and has maintenance – moving parts)
Put numbers in the accuracy boxes
Initial setup vs daily setup

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
This is easiest way (use this most often)

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.
Must measure instrument height

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

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

19. What can go wrong? TS out of calibration Bad setup Bad TS Location
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?