![]() ![]() You should take care to note whether your GPS provides this value in feet or meters. It might also be available on the front data display of some GPS. This is normally contained in the GGA and GGK messages. Once your GPS is stable and in RTK mode, write down the height of the GPS antenna above the reference ellipsoid. Measure the distance from your GPS antenna to the water level surface (c). ![]() ![]() Write down the water level from the tide staff (b). The staff should be referenced to the local chart datum. Set up your GPS adjacent to your tide staff. ![]() The following steps should be taken at each location to determine the separation between the reference ellipsoid and the chart datum.įigure 2: Determining the separation between the reference ellipsoid and the chart datum If your survey is conducted over a large area where the separation between the ellipsoid and chart datum changes, you will need several points to the difference. If your survey is conducted in a small area, you may need only a single point. When the RAW data file from the SURVEY program is read into the Multibeam editor, each sounding will have an RTK Tide correction, based on the method shown above.ĭetermining the Separation between the Reference Ellipsoid and the Chart Datumīefore you head out on the water to start your survey, you need to determine the separation between the WGS-84 reference ellipsoid and the local chart datum. The sign of value (d) is negated by HYPACK(TM) to be consistent with our normal tide correction values. When correctly configured, HYPACK(TM) computes this value at each RTK GPS update and saves the position and a tide correction to the raw data file. (c) is the height of your GPS antenna above the static water line. (b) is the height of the GPS antenna above the reference ellipsoid. (a) is the height of the reference ellipsoid above the chart datum. Where (d) is the height of the water surface above the chart datum. How we determined this is explained in the next section. In our example, we have pre-determined the reference ellipsoid is 100m above the chart datum. If we can determine how high the reference ellipsoid is above the chart datum, we can then solve for the water level above the chart datum. The RTK GPS is reporting that the GPS antenna is 80m below the reference ellipsoid. Our measurements show the antenna height to be 15m above the static water line. The figure to the right shows a survey boat using RTK GPS to determine the current water level correction. All Rights Reserved.Figure 1: HYPACK(TM)'s method of obtaining real time water levels Registered Office: Xylem Analytics UK Ltd., Xylem, 7 Dunham's Court, Dunham's Lane, Letchworth Garden City, England, SG6 1WB, UK. VAT No. VAT No. GB 220 3350 25Īanderaa, Global Water, MJK, Royce Technologies, SonTek, WTW (process products) and YSI (environmental products) are all Xylem brands operating in the UK from Xylem’s Letchworth facility. Registered Office: Bellingham & Stanley Ltd., Xylem, Longfield Road, Tunbridge Wells, Kent, TN2 3EY, UK. Transparency in Supply Chainsīellingham + Stanley, ebro, SI Analytics, OI Analytical, WTW (lab & field products) and YSI (life science products) are all Xylem brands operating in the UK from Xylem’s Tunbridge Wells facility. Read more about this in our Privacy Policy. We use cookies and beacons to improve your experience on our site. Learn more about Xylem and Xylem Analytics. Specifications on all products subject to change at any time. Website: Aanderaa, Bellingham + Stanley, ebro, Global Water, HYPACK, MJK, OI Analytical, Royce Technologies, SI Analytics, SonTek, WTW and YSI are trademarks of Xylem Inc. With users spanning the range from small vessel with just a GPS and single beam echosounder to large survey ships with networked sensors and systems, HYPACK® gives you the power needed to complete your task in a system your surveyors can master. Whether you are collecting hydrographic survey data or environmental data, or just positioning your vessel in an engineering project, HYPACK® provides the tools needed to complete your job. It provides the Surveyor with all the tools needed to design their survey, collect data, process it, reduce it, and generate final products. HYPACK® is one of the most widely used hydrographic surveying packages in the world, with more than 10,000 users. Founded in 1984, HYPACK, INC (formerly Coastal Oceanographics, Inc.) has evolved from a small hydrographic consultant to one of the most successful providers of hydrographic and navigation software worldwide. HYPACK - A Xylem Brand is a Windows based software for the Hydrographic and Dredging Industry. ![]()
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