Accession Number : ADA304368

Title :   GPS Tides: A Project to Determine Tidal Datums with the Global Positioning System.

Descriptive Note : Rept. for Oct 93-May 95,

Corporate Author : ARMY TOPOGRAPHIC ENGINEERING CENTER ALEXANDRIA VA

Personal Author(s) : DeLoach, Stephen R.

PDF Url : ADA304368

Report Date : AUG 1995

Pagination or Media Count : 111

Abstract : The recent development of On-The-Fly ambiguity resolution techniques with Global Positioning System (GPS) observations has created a powerful tool for the study of dynamic time series, such as tidal analysis or the study of water level heights. For this project a GPS receiver was successfully operated on board a Canadian Coast Guard navigation buoy. Ten days of data, at a one-second sampling interval, were collected at a station in the open waters of the Bay of Fundy, followed by ten days from an inshore mooring. The buoy data were transmitted in real time to a reference station on shore where antenna heights were computed in real time. Subsequent processing reduced the 1-Hz antenna height series to a 15-minute water surface height series for comparison to two nearby 'conventional' gauges. These were the Saint John Harbour permanent gauge and a temporary Socomar pressure gauge. Mean tide heights computed from the inshore data are all within 1 centimeter. The means, computed from the inshore series, differed by 20 centimeters between the buoy and the 'conventional gauges,' indicating a differential slope between the water surface and the ellipsoid. In addition to the water surface. measurements, about 20 days of GPS data was collected from a static baseline to characterize the performance of the On-The-Fly GPS system, without the influence of a moving platform. From the 20 days of data, 97 percent is within 3 cm of truth, while the mean daily heights are about 0.3 cm below the truth. This project has demonstrated that the 'GPS buoy' is a viable method of tidal datum determination and it should be possible to use the ellipsoid as the basis for water surface datums. (AN)

Descriptors :   *OCEANOGRAPHIC DATA, *GLOBAL POSITIONING SYSTEM, *OCEAN TIDES, DATA BASES, DATA MANAGEMENT, OCEAN SURFACE, REAL TIME, INSHORE AREAS, RESOLUTION, CANADA, TIME SERIES ANALYSIS, ACCURACY, PRESSURE GAGES, TIDAL CURRENTS, DATA REDUCTION, DATA ACQUISITION, HYDROGRAPHIC SURVEYING, HARBORS, DIURNAL VARIATIONS, SHORES, OPEN WATER, BUOYS, FUNDY BAY, FLOATING PLATFORMS.

Subject Categories : Physical and Dynamic Oceanography

Distribution Statement : APPROVED FOR PUBLIC RELEASE