Heaps commented ‘The Trimble system was selected because it is very easy to use and importantly we can swap between a variety of differential correction sources for improved accuracy and coverage.As well as the reference station and telemetry system, we are able to easily use public differential corrections (IALA). The ability to seamlessly swap between local and public corrections has proved a great benefit when working in different areas and noticeably reduced the number of lines which must be resailed due to loss of differential correction.’

The positional data is used in conjunction with large quantities of time stamped bathymetric data, which is collected with specialised hydrographic software. Data is then taken back to the office ashore where it is processed, quality controlled and presented, usually as paper charts for immediate use by pilots bringing large vessels into the Port.

Typically these vessels may sail with as little as 1.5m under their keels so it is vital for Heaps and his team to know precise depths and exactly where any shoals are located so that dredgers may be accurately tasked to maintain advertised depths. Collected data is also supplied to the UK Hydrographic Office in Taunton for incorporation into their Admirality Charts.

The new Trimble DSM232 and RDM232RS will be used for other tasks where precise marine positioning is required, from navigation mark deployment and checking to incident response. By supplying a constant time string from the second data port which is used to synchronise all the time clocks on the port computer network, the Port can now ensure that all computers, radars, tide and weather recording systems, and data records are synchronised within a fraction of a second. Collected data is also being used for other applications, including 3D visualisations, numerical modelling and the creation of electronic charts for use on board dredgers.vessels.

MJ Information No: 22715