1. Setting Up a New Site for GPS Operations

2. Benefits of a well planned setup
Setting up the site right – the first time!
Reduces setup errors, which could result in rework
Reduces time wasted on multiple equipment setups and site visits
Increases productivity of machines and field crews
The project is completed faster!
You save time and make more money!
Multiple GPS setups due to poor planning on a site could result in site systems providing erroneous information which could cause rework and added project costs
Setting the site up correctly the first time will enable site crew to work on getting the project completed, rather than wasting time on subsequent equipment setups
When the site is setup correctly the productivity of machines and field crews is increased - when multiple setups are performed, the machine and site positioning systems go down until the site is setup

3. Setting Up a Site for GPS -Topics
Preliminary preparation
Site reconnaissance
Setting up the site
Site Calibration
Conclusion

4. Preliminary preparations
Digital data – What do you have?
CAD data
3D Model
Who is responsible for control?
Owner or you?
Resources to perform in-house or contract
Trimble Connected Site preparedness
Internet connectivity (Land Line vs Cellular)
IBSS
2-Way data

5. Digital Data CAD data must always be verified
CAD data often must be corrected and/or enhanced
Trimble Business Center – Heavy Construction Edition (HCE) data prep module can provide you with the tools to perform this task
You should understand the needs of office systems vs field systems and learn what formats are needed

6. Control What is control?
A set of points by which everything is referenced to
They should be set with a high degree of accuracy
Usually have been network adjusted (TBC Advance Survey Modules can be used for this)
Control points are measured to “calibrate” the site for GPS-based systems
You need a minimum of 3 and 5 or more are recommended
Do control points exist on site?
Check the site plans for control point lists and locations
Check with engineer

7. Control Point Locations
3 points
will work, but yields only 3 baselines
Geometry could be weak
Control should encompass the entire site

8. Control Point Locations
4 Points
Better, 6 baselines
4th point - independent height check
Geometry is stronger

9. Control Point Locations
Optimal control-
Multiple control points
Geometry strongest, balanced
Points encompass the site.
This example - 7 points, 18 baselines.

10. Connected Site Connecting your site enables Remote transfer of designs
TCC or - Rovers
TCC or 2-Way data - machines
Remote Productivity reporting
Work Order results from SCS900
Productivity tag files from machine
Remote troubleshooting
Trimble Assistant
2-Way data
RTK Correction source delivery
IBSS
VRS

11. Connected Site Things to be aware of Internet Connectivity
LAN – Comcast, Cox, etc.
Stable & faster transfer rate
Cellular – At&t, Verizon, T-Mobile, etc.
Peak use outages
Will you be using remote correction source?
VRS
Private or government
IBSS
Managed or Unmanaged
Remember - these are things beyond contractor control

12. Site reconnaissance Size, duration, and environmental considerations
Control verification
GPS base station locations
Correction source delivery

13. Size and duration of the site
Size and duration of site dictates:
GPS base station setup
Semi-permanent installation vs daily setups?
Connectivity
Fixed GPS and radio network infrastructure
Linear versus enclosed
IBBS / Local Base
VRS (Virtual Reference Station)
Rebroadcast
ITEMS TO MENTION:
Optimally you would want to set up a site base central to the site surround by control used in calibration
Conditions to keep in mind on linear projects – the first red circle indicates the primary base station location might be sufficient for radio coverage for the west side of the job, but not for the east side of the job – size of the site might dictate use of radio repeaters and / or a second GPS base station location to ensure full coverage of the job site
Range Limitations K based on line of sight, Cellular allows for significantly extended range from the base station, Correct radio antenna, High gain vs. Low gain or directional
PPM error 1cm +/- 1ppm (+/- 1 millimeter for every kilometer away from base, e.g. 20km distance would equate to 1cm +/- 20mm)
= GPS Base Station
= Radio / Repeater

14. Environmental considerations
Undulating versus flat terrain
Urban canyons and dense foliage
Radio Interference
Airport radio
towers
Microwave towers

15. Control Do control points exist on site?
Check the site plans for control point lists and locations
Check with engineer
How many? You need a minimum of 3 and 5 or more are recommended
Do they provide good GPS visibility?
What is there geometry relative to the site?

16. GPS base station - Location
Set GPS antenna with 360° view of the sky. If limited try to set up with clear visibility to the equator.
GPS 55° latitude limit
Glonass 65° latitude limit
Avoid sources of multipath
Chain link fence
Trees
Flat, reflective surfaces
Setup GPS base radio link for maximum range
Elevate the radio antenna to increase range
Correct antenna (high gain and low gain)
Avoid sources of RF interference
Microwave, radio towers
Power lines
Multipath occurs when a GPS antenna receives a GPS signal both directly from the GPS satellite and after it has been
reflected The reflected GPS signal interferes with and corrupts the direct GPS signal, causing position errors

17. GPS base station Accessibility Power sources
Access to where it can easily be configured, monitored, serviced, and connected to via PC
Power sources
Permanent or fixed power sources are ideal for long term projects (AC / fixed generators)
Portable power sources - Ideal for daily usage or to provide back up to fixed power (batteries, solar panels, etc)
Conditioned power is ideal to prevent power “spikes” to reduce system damage & outages
Theft and vandalism mitigation
Permanent setup - recommend a fixed, secure location
Portable setups for rapid daily use and tear down
It is important to know if a constant permanent source of power is available on site, such as a site generator, AC power from a site trailer or if a portable power source would be required, such as a marine battery on trickle charge by a solar panel or internal batteries
It is important to note the local surroundings and inquire with site personnel as to whether theft or vandalism is prevalent on the job site – if so, find locations where equipment can be safely and securely stored or hidden on site, such as a job trailer with dead bolt locks, otherwise daily setups of the equipment could be required to mitigate theft. In locations that theft is a possible issue consider use of a modular receiver.

18. GPS base station RTK Correction source options
Site Base corrections via radio
Semi-permanent or Portable
Local Base (over internet)
Private Permanent base
COORS
IBSS (Internet Base Station Service)
Trimble over internet solution
VRS
Rebroadcast (IBSS, Local Base, VRS)
Connecting SNB900 to Base over internet and re-transmitting over radio
ITEMS TO MENTION:
Local Base - L5 signal will provide better long baseline solutions which will begin to make this a more popular solution
Local Base, VRS, and Rebroadcast are commonly connected to via cellular
Rebroadcast will allow machine operation but caution distance from base due to noise/PPM error

19. Setting up the site Why do we need a base Station?
To achieve millimeter level accuracy we utilize an RTK solution. RTK navigation uses a base station receiver and mobile units
What does the base station do?
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
Considerations
GPS base station types
GPS RTK Correction delivery

20. GPS base station types Modular – SPS852
Smart Antenna (Mobile) – SPS882

21. Modular GPS base station
Semi-permanent “modular” GPS base station
Installed on permanent structure for duration of construction project
Ideal for large projects, when multiple grade control and site positioning systems are in use

22. Mobile GPS base station
“Mobile” GPS base station for daily setup
Easily setup
Portable to different sites or different locations on large site
SPS852 can also be used in this configuration
AutoBase
SPS882 & SPS852

23. Mobile GPS base station
AutoBase Feature
SPS882 & SPS852
12 base location memory
50 meter rule
AutoBase Warning – SPS852

24. GPS RTK Delivery Method
Internal radio or External radio
450 MHz and 900 MHz
.5W, 1.0W, 2.0W, High Power TM3/HPB/TDL
Internet Base Station(IBS)
Increased range limited to PPM error deemed acceptable
Cellular
Ethernet LAN

25. Setting up the GPS base station
The Good…
Ideal location for semi-permanent installation – GPS antenna and external radio antenna mounted on steel “T-bar”, 360 degree view of the sky, GPS receiver and power source secure in locked area inside structure

26. Setting up the GPS base station
The Bad & Ugly…
Poor installation because:
Portable GPS base station, blocked by trees and metal building, limited view of the sky – bad installation

27. Moving the GPS base station
Before calibration – no problem
After calibration – location requirement
Must be moved to point used in calibration or control point measured while using calibration
Same rules for calibration obtained under VRS

28. Setting up the GPS base station
Common mistakes
Antenna height errors
Switching antennas
Changing type, APC difference
Moving base to unknown point
Moving base to point measured in different reference frame

29. GPS site calibration
What is it…
Requirements

30. NEE GPS site calibration What is a site calibration? GPS Coordinates
A measurement procedure that defines the relationship between GPS coordinates and local coordinates
GPS in Latitude, Longitude, and Ellipsoid Height
Local Coordinates in Northing, Easting, Elevation (MSL)
We are pairing coordinates on a sphere surface and to those on a flat planar surface
GPS
Coordinates
NEE

31. GPS site calibration Residuals
Best effort translation between pairs (Control & WGS-84)
SCS900 has a Tolerance for Calibration
Value should be 50% of acceptable project tolerance
Tolerance used to test calibration result worst residual
We use a least squares fit – Control (assumed correct) & GPS WGS-84(errors)
ITEMS TO MENTION:
SCS900 has a Tolerance for the Site Calibration – this value should be at a maximum 50% of what your accepted tolerance for the project is. This tolerance is used to test the calibration result worst residual. If the calibration passes then you are good to go (but cannot try to improve the cal further – if you want to do better than the tolerance you need to change the tolerance to a tighter value)
If SCS900 fails, what it does is compute the calibration n-1 times (where n is the number of points observed). Each computation uses all but one of the control points. The best calibration result will not include the point that has the most negative affect on the calibration (Hz or Vt). The worst point and worst error is flagged by the software (Hz or Vt) and that component of the point can be rejected. At that time SCS900 recomputes the Site Cal again, and checks to see if it passes tolerance. If it does you are good to go, if it fails it repeats the same process with the remaining points. It will do this loop until it gets a cal in tolerance or until the user accepts a lower tolerance. The maximum tolerance you can put into the site calibration is 0.2’.

32. GPS site calibration Why is a site calibration required?
Allows GPS-based rover systems to work in your local site coordinate system
What is needed for site calibration
Onsite control base on local coordinates
= GPS observation
= Control Point

33. GPS site calibration Multi-point site calibration Requirements
Minimum of 3 (3D) control points
Recommend 5+ control points with good geometry for better results
Combination of horizontal and vertical points - Minimums
3 horizontal control points & 3 vertical control points
– or –
1 vertical + 3 horizontal + Geoid model
Used when control exists and references a design frame
= GPS observation
= Control Point

34. GPS Site Calibration Control point network geometry is key
= Poor network geometry
= Ideal network geometry
For multi-point site calibrations, control points geometrically arranged in a “line” or “clustered” in one area on the construction site is undesirable.
Error in position dramatically increases the distance traveled outside calibrated site area.
It is ideal to have 5 or more control points, good “geometry” of control, in the center and around the extents of the project for better site calibration results
Enclose the project area with control
More control points and good network geometry can improve site calibration results and identify problems early

35. Conclusion In conclusion, remember the key site setup steps
Site reconnaissance
Size, duration, and environmental considerations
GPS base station location
Setting up the site
GPS base station setup
Site calibration

36. Questions?