1. Philadelphia District
US Army Corps of Engineers

2. RTK-GPS for Dredging Why Where How Much The Pay Back – Time - Accuracy
Production monitoring
$$$$

3. RTK-GPS for Dredging WHY
Improved Accuracy for both positioning & depth
Knowing the exact draft of the vessel enables increased accuracy for dredge cuts
Decrease possibilities of missing spot shoals
Dredging around piers & pilings
I am sure you know more reasons than me to improve dredge position accuracy

4. RTK - GPS Becomes VRS – RTK - GPS
Virtual Reference System -
RTK – GPS !!!!
What next !!!!

5. Virtual Reference Station RTK - GPS
No more negotiating with local residents or businesses to put equipment up for the duration of a project
No more dead batteries or power failures slowing or stopping work
No more radio interference causing incorrect positions

6. Virtual Reference Station RTK - GPS
What is this new term?
VIRTUAL - RTK- GPS

7. Virtual Reference Station RTK - GPS
Defined – A number of Continually Operating Reference Stations (CORS) connected by a network that computes real time (1/sec) GPS measurement corrections for an intermediate position used as a base station (virtual) when conducting RTK-GPS surveys.

8. Would you like to:
Have your Dredge show up for a job and just start working
Not worry about tide stations
Cut Accurate side slopes
Not worry about cutting too shallow or too deep
Accurately monitor production

9. VRS-GPS Can be integrated with
COE Silent Inspector
Hypack – Dredge Pack
Other custom -production monitoring programs
Replace the images with better ones

10. VRS – RTK - GPS Where did it come from?
COE & DOT survey departments looking to improve efficiency and repeatability when performing surveys
Being used in Europe by many industries
Commercial groups are starting networks

11. RTK-GPS for Dredging Where
At this moment it is coming online in the Philadelphia District
Once fully established in Philadelphia it is planned to expand through NAD
We have received inquiries from various districts in SAD & MVD

12. RTK-GPS for Dredging Where
USA
Various State DOT Departments
Commercial groups
Colleges & Universities
COE - Philadelphia

13. VRS - RTK-GPS for Dredging Where
North Carolina Geodetic Survey
South Carolina Geodetic Survey
Minnesota DOT
Ohio DOT
Texas DOT
Puget Reference Network (Washington State)
Texas Cooperative Network
University of Minnesota

14. RTK-GPS for Dredging Where
Europe
Austria, Belgium, Denmark, Finland
Germany, Norway, Sweden
Switzerland, United Kingdom
Japan

15. RTK-GPS for Dredging How Much?
Typical Dredge installation
RTK-GPS receiver = $20,000
Laptop / work station = $3,000
Proxy-Cast Cellular Network Router = $1,000
Total - $24,000

16. VRS-RTK-GPS Typical Components
Laptop
Proxy Cast Cellular
Data Collector (optional)
RTK-GPS receiver

17. VRS base position update
The default base station position remains fixed at the initial position determined during the first connection of the day
Optionally the VRS base location can be set to update at specific intervals from the original location
Good option for Hydrographic and Beach surveys

18. Philadelphia District VRS-GPS Network
Network map showing existing stations and baselines
Network densification may be needed to improve 3d positional quality
413 Km N-S 202 Km E-W
12 Operation Net RS now 14 Planned Net RS receivers
Philadelphia District VRS-GPS Network

19. USACE VRS-GPS Network In Production
The Following Slides show some of the areas that the VRS-GPS Network is being used to improve Production
New Projects and Applications are Being added to the List

20. VRS-GPS Rover Deployed in Remote Areas
Rover antennas are either in continuous record mode, attached to the airboat having measurements referenced to the bottom of the airboat or on a standard survey rod and stop and go measurements are made
VRS-GPS Rover Deployed in Remote Areas

21. VRS-GPS Rover Deployed in Remote Areas
Quick survey team response
Little or no stable control in the area
Often calibration is performed several miles outside of the immediate project area
Fast data acquisition
Accuracies within project tolerances (0.1’v)
Additional Rovers for data collection

22. ATV - Used for Beach Surveys
The ATV is used for pre and post beach surveys. The rover antenna is attached to the ATV using a quick connect. Most Surveys are done using continuous mode The ATV serpentines along the beach continually crossing the required contour elevation. When areas requiring details are encountered the antenna is mounted on a standard rod and details are acquired.
Using the VRS-GPS network the survey team was able to complete the post storm surveys or 5 islands in one day. A drastic improvement over the 2 days per island that was the standard a few years ago.
ATV - Used for Beach Surveys

23. ATV – Used for Beach Surveys
Immediate Response to Pre and Post Storm Surveys – Destroyed Control is No Longer an Issue
Regional Models are Now Surveyed with a Uniform Control Network – Island to Island Network Variations are Eliminated
Contractors can be Given a User Name & Password that is Active while working on COE Projects

24. RTK / NOAA Ports Comparison
Single Baseline Base
185’ Light House
85 Watt Radio
~163 MHz VHF
10 to 30 Km
0.1 to 0.25 tide comparisons
Using Geoid 2003

25. RTK / NOAA Ports Comparison
Delaware Bay
Brandywine Light
10 KM from RTK Base
<0.1’ Difference
Repeated readings
Various tide / current conditions
Various GPS constellation conditions

26. RTK / NOAA Ports Comparison
Delaware Bay
Ship John Light
30 KM from RTK Base
+/-0.2’ Difference
Repeated readings
Various tide / current conditions
Various GPS constellation conditions

27. RTK / NOAA Ports Comparison
Single Baseline
0.1’ to 0.3’agreement
VRS-GPS
Constant 0.1’ agreement
Testing Continues
Full Documentation Before Implementation

28. Navigation Surveys & Dredging
Survey Vessel With VRS-GPS Installed

30. Monitoring Dredge Production Using VRS-GPS
COE Silent Inspector
Hypack – Dredge Pack
Other custom -production monitoring programs
Replace the images with better ones

31. Monitoring Dredge Production Using VRS-GPS
Current Dredge Monitoring Techniques
GPS using USCG Differential = 3 to 5 m Hz & No vertical component
Nav Sat = Horizontal ? & No Vertical component
Pressure sensors for draft & load measurement +/- 0.5’ typical
RTK – GPS = 0.2’ Vertical

32. One More Example Production Monitoring
Typical Hopper Dredge Capacity
100’ long x 20’ wide = 2,000 sq ft
+/- 0.5’ pressure sensor = +/- 37 yards
+/-0.2’ RTK-GPS = +/- 14 yards
37 $25.00/ yard = +/- $925.00
14 $25.00/ yard = +/- $350.00
It adds up in the long run

33. Just some food for thought
The survey industry is heading in this direction
A uniform control network in the region
Cellular connections Vs Radio
Accuracy is constantly monitored by the network operator
Accounts can be setup and billed as used or you can become a network partner

34. Questions or Comments
Some of the items discussed in this presentation are application ideas developed by the author and not presently in production or use by the COE