Hydrographic ServiceThe PLA Hydrographic Service provides a wide range of services to river users. Continuous monitoring of the river and estuary are essential to the safe navigation of the Thames. Regular surveys are completed of the tidal Thames from Teddington to the Outer Estuary. Many types of survey are carried out - main, periodic, engineering and berth surveys are all now produced digitally to improve efficiency and accuracy. Tide and current information is also obtainable, both as live and historical data. The PLA is ISO9001 accredited and as such all hydrographic surveys are subject to prescribed procedures. Click below to view a short film about the PLA's Hydrographic Service
For many years the surveyors of the PLA Hydrographic Service have been actively involved with national and international hydrographic matters, holding responsible positions with FIG, RICS and the Hydrographic Society. All methods and equipment are exhaustively tested and the officers regularly present their findings at surveying conferences. To contact the Hydrographic Team please use this Enquiry Form. New - PLA Colour ChartsClick here for details of the PLA's newly launched A2 Coulour Charts suitable for navigational use. SurveysMain River Surveys
Main river surveys cover the river from bank to bank and are typically produced at a scale of 1:2500. They usually cover a stretch of river about 2.5km long. These are carried out, on average, every 8 years. Each survey covers a river reach or part of one.
Estuary Surveys
These cover the area from Sea Reach 1 Buoy out to the PLA seaward limits and are repeated every 10 years on average. The data is then sent to the Admiralty to be incorporated into the UKHO charts of the Estuary.
Click on the image to enlarge (26kb)
Periodic Surveys
Within the River and Estuary, periodic surveys are completed of the shoal areas and channels that frequently change. These are vital to the safe navigation of the Thames. Scales vary depending on the area covered by the survey. Click on the image to view a Periodic Survey sample PDF (56kb)
Other Types of Surveys and Charts
Click on the image to view a sample PDF (53kb) PLA Miniplots are a series of small scale A4 charts showing the latest significant depths from the larger scale surveys. Miniplots are available online. Other surveys are done at the request of various parties, both public and private. Examples include pre and post-dredge surveys, engineering surveys and those for river development works. Using the latest multibeam technology the PLA Hydrographic Service conducts high resolution structural surveys on jetties and bridge piers for civil engineers. The Service is becoming increasingly experienced with gathering environmental data for studies into the effects of river works and dredging operations. Charts - Other InformationAreas covered by each type of chart can be found by contacting the Hydrographic Service. Use the online chart catalogue to find the Main Survey chart that covers your area of interest. PLA Charts show depths in metres and decimetres, all tidal heights and depths are in metric units. River surveys are based on the Ordnance Survey of Great Britain, with a National Grid graticule shown on most surveys. Estuary surveys are based on UTM Zone 31 and also show a WGS84 geographic graticule (latitude and longitude). The Charts are compiled from the surveys of Rivers and Creeks. As new information is gathered they may be corrected by Chart Correction Advices. These are serially numbered for each Chart. Topography is based on Landline data supplied by the Ordnance Survey. This information is amended at 3 monthly intervals by OS and verified by PLA when the surveys are taken in hand, but the data remains Crown Copyright. Soundings in the River and Estuary are reduced to a local Chart Datum, which approximates to the Lowest Astronomical Tide. Select the link for further information about Chart Datum and Ordnance Datum. Tidal Information
The Hydrographic service is also responsible for maintaining the 16 recording Tide Gauges along the river and estuary. Our tidal technician regularly visits sites to ensure the continual smooth running of the gauges. Click on the image to enlarge (45kb)
Live tidal information is available online and is broadcast every half hour on VHF Channels 14, 69 and 68. High and Low waters for the current year, for each tidal station is also available. Historical data dating back to 1993 is available digitally. Current and predicted tides can also be requested. Please note that charges are made for these services Meteorological effects and variations in fresh water flow from the upper Thames can cause marked differences from predicted heights and times. In conjunction with the Environment Agency and HR Wallingford, a 2D model of the river flows has been developed to aid in the decision making process, including River Works Licensing and Flood Risk Management. Other Information Available From The Hydrographic ServiceHeight information for bridges across the Thames is available. Positional information can be made available, for example width of the channel, location of tunnels, overhead lines etc. Survey data and other information, for example Conservation Areas or the location of new developments can be compiled to form chartlets on request. Equipment and Tools
The Hydrographic Service operates three survey craft - see "About our boats" for details. The PLA has adopted DGPS as its primary positioning system from the City of London to the Outer Thames Estuary and transmits its own GPS correction data in the RTCM format from two sites on VHF radio. Both major vessels are fitted with Reson multibeam systems and DGPS aided Applanix POSMV inertial reference units. The Verifier has the Reson 8101 MBES and is used predominantly in the Estuary and the Yantlet is fitted with the Reson 8125 and conducts navigation and structural surveys mainly in the river. The whole chart production operation is now digital, using the latest GIS technology, and the PLA Hydrographic Service is in the forefront of ports producing IHO S57 data.
PersonnelThe Hydrographic service presently consists of:
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