GS1-2-3-4 Goodwin Sands - United Kingdom Hydrographic Office

7.3 The assessed accuracy of depth measurements was +/-0.38 metres (2 sigma) and met
the required standard. The survey data was processed at a scale of 1:25,000.
8. 2006 SURVEY DETAILS
8.1 The survey of areas GS1 and GS2 (focused) was conducted from 2 to 10 September.
Weather in the area was initially poor and on 6 September deteriorated, with the vessel
breaking off surveying. The weather had improved enough by 10 September to
complete the survey.
8.2 Survey data was acquired using a Kongsberg 3002D multibeam echosounder system.
8.3 The Primary Reference Position was provided by Applanix POS MV systems, supplied
with GPS data from a Real Time Kinematic (RTK) system, using GPS carrier phase
measurements observed at an installed Geodetic Control Station in Margate. The
survey met the accuracy requirements for an IHO Order 1 survey.
8.4 The shallowest part of GS1, with depths of less than 5 metres, was surveyed at the end
of the survey period, following a 4 day break in operations. Where these lines overlap
with those run 5 days earlier, there is a significant change in the shape of the bank.
The profile below shows the extent of change that occurred between 5 and 10
September, with over 2 metres of sediment accumulating and a steep southern slope
forming (Figure 5.1).
2 m
80 m
South
Figure 5.1: Survey line cross-sections (Blue 5 Sept, Red 10 Sept)
North
8.5 Examination of WaveNet data for Hastings and West Gabbard shows increased
significant wave heights during the period, with wave heights exceeding 2 metres at
both sites. Over the course of a year, these wave heights are not exceptional and it is
likely that over the shallowest part of the bank sediments are regularly reworked with
changes in wave energy, direction and tidal factors.
9. 2009 SURVEY DETAILS
9.1 The four Goodwin Sands areas were surveyed from 23 July to 1 September, in
conjunction with four Dover Strait areas. Weather in the area was generally good
throughout the survey period, with slight to smooth sea states. Survey work was
undertaken by two vessels, surveying in the Goodwin Sands areas for 16 and 25 days
each.
9.2 South Calliper had extended outside the established survey limits (with the 10 metre
contour migrating up to 1,000 metres), although the survey work was not adjusted at
Assessment Goodwin Sands/2009 – Original Page 8 of 51