Philadelphia District US Army Corps of Engineers

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Navigation Surveys & Dredging Survey Vessel With VRS-GPS Installed

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

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

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 yards @ $25.00/ yard = +/- $925.00 14 yards @ $25.00/ yard = +/- $350.00 It adds up in the long run

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

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