1. Using GPS Laser Offsets

2. The Basics of GPS Technology

3. Global Positioning System (GPS)
Space Segment
your location is:
37° ’ N
122° ’ W
Control Segment
User Segment

4. Errors in GPS Obstruction Multipath Atmospheric conditions Clock bias
Receiver hardware
User
There are multiple sources of error in GPS.

5. Multipath & Obstruction

6. Minimizing Errors Post-process your GPS data
Wait for good satellite coverage
Use an offset!

7. Maximize Productivity
Use antenna on a range pole
Maintain GPS lock between features
Maintain view on 5 or more satellites
Don’t expect best results in harsh environments
Use an offset!

8. Other reasons for an Offset
You can’t get there (private property or behind a locked gate)
You don’t want to go there (it’s not safe)
You can be more productive from one spot (map multiple features)

9. MAP THIS.
STAND HERE.
MAP THIS.
STAND HERE.
MAP THIS.
STAND HERE.
MAP THIS.
STAND HERE.

10. Measurement Values 101: The basics

11. Software Integration

12. About Compass Technology & Helpful Field Tips

13. Compass Sensing
FACT:
Local magnetic interference will cause accuracy breakdowns – regardless of what compass you use.

14. Be Aware of Proper Magnetic Hygiene
Your Person
Eyeglasses, cell phones, pager, watch, clip board, etc.
Your Environment
Vehicle, building, power lines, etc. (20’ separation)
Your Equipment
Data collectors & GPS systems (18” separation)

15. The MILLION DOLLAR Question:
NO!
Can you use a compass from inside your vehicle?
YES!
Can you still perform laser offsets from your vehicle?
Using a Range Triangulation Method

16. Compass Calibration Moving from one job site to the next
Major change in temperature
Major change in battery voltage

17. Simple Field Test to Determine Magnetic Interference
Target / Step Test
1.) Choose a target, shoot it and note the azimuth.
2.) Step along the sight line and shoot the same target again.

18. Summary: Why Offset? Poor GPS coverage Inaccessible target
Unsafe to reach
Increase efficiency

19. Questions?

20. Contact Information
Jay Riester
Mapping Tech Support