OTF DGPS for estuarien dredging and sounding surveys
This report assess the feasibility of using the On-The-Fly Differential Global Positioning System (OTF DGPS) satellite positioning technique for the accurate and reliable measurement of spatial variations in water’s surface elevation in an estuarine region. The improvement of the accuracy and reliability of squat-dependent dredging and sounding surveys is assessed. Conventional dredging and sounding surveys require the installation and maintenance of temporary water level sensors, along with water level interpolation at the vessel location. OTF DGPS feasibility is assessed through a practical field exercise on the Mirimichi River, new Brunswick, using a representative OTF DGPS system – the Ashtech Z12/PRISM system. Z12/PRISM results, obtained with the collaboration of the Department of Public Works, are compared with reviews on the performance of the other OTF DGPS systems. Under limited condition: (1) PRISM/Z12 water surface elevation accuracu was acceptable, being +/- 0.034 metres at 95% confidence, and (2) PRISM/z12 reliability was acceptable. Availability was: (1) acceptable at 90-99% for three out of four survey days, and (2) unacceptable at 25% for one survey day. A squat-independent approach for the OTF DGPS dredging and sounding surveys should be investigated. The use of multiple base and remote OTF DGPS stations needs to be investigated. The accuracy and reliability of OTF DGPS needs to be assessed further, especially during the upcoming sunspot maximum.