Under Wharf Bathymetry
Hydrographic survey equipment, is the Ceeman data measurement and recording system, which provides full hydrographic standard survey measurement and will meet or exceed the IHO S-44 Order 1 specification.
This equipment is specifically designed for use in shallow water and can measure depths to as little as 0.6m below the surface.
All standard checks of equipment performance, as specified by IHO S44 will be applied and recorded during the course of field operations. Vertical accuracy of the single beam and duel frequency transducer is+/- 0.05m measured from the surface of the water.
Tides will be monitored using KGPS mounted on the vessel logging height shots every 60 seconds during the hydrographic operation.
The KGPS supplies position to the equipment to a horizontal accuracy of +/- 0.03m. The guidance computer tracks and records real time position to continuously monitor horizontal accuracy.
Under Wharf Methodology
The duel frequency transducer is mounted on a specially designed raft (transraft) which in turn is connected to a calibrated pole that can be extended 25 m.
The transraft is pushed under the wharf or pier from a stationary vessel tied in position between the pile rows.
The vessels position is logged on the guidance computer and becomes the measure point for the calibrated pole.
The transducers information is feed back to the operator continuously in real time. At any distance under the wharf both frequency's depths arenoted directly to a custom designed electronic proformer.
The proformer can be customised to suit the clients requirements.
Typical fields in the data base are:
- Real time depth for each frequency
- Real time horizontal position
- Time stamps for tide reduction
- Steel plastic or timber pile &size
- Comments
When the tranraft has been pushed out to the its maximum point it is simply retrieved and the vessel is moved up to the next pile row and the process repeated.
The whole under wharf survey process as been designed so both the crew controlling the transraft stays seated. At no stage does the methodology require a vessel or operator go under the structure.
Vessel will be: "Redmap", a 4.55m Polycraft centre console vessel. Specially set up for hydrographic survey. It is powered by a 40hp fourstroke Yamaha outboard and is MSV registered, class 2D. Operated bya qualified coxswain
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