Thomas Lawrence

Introduction

The Thomas Lawrence was a Danish, 18th Century schooner, which sank off the south coats of England in 1862. It was discovered by divers in 1983 and subsequently excavated in 1985. Since then the position of the wreck has been unclear and it has proved difficult to re-locate despite a number of attempts. The wreck was reported to be located in the south-western part of the survey area for this stage of the project and initial documentary research provided five possible locations for the site. As part of the area survey Wessex Archaeology found a wreck believed to be the Thomas Lawrence and have been able to provide its precise location.
 

Detailed Results

The wreck was identified from the sidescan sonar datasets during initial processing, though the site was not consistently interpreted as being a wreck. The site was only located on two of the datasets after correlation of all the data in the GIS. Images of the site from each of the sidescan sonar data sets demonstrate the varying quality of the data.
 
 
In all, the Thomas Lawrence was identified 21 times out of a possible 36 in the sidescan sonar data with the positions from these sites covering an area approximately 60m (N/S) by 55m (E/W).
 
The wreck was only positively identified as a wreck or possible wreck site on two of the datasets (500kHz and 100kHz both at 50m range settings) during the initial processing.
 

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Although the site was constantly identified as an anomaly at both high and low frequencies and on all range settings, it was not consistently identified as a wreck. Only the data acquired with the 50m range setting provide sufficient resolution for structures to be identified within the wreck, although these structures are just linear reflectors and not identifiable parts of the wreck.
 
In addition, the nature of the survey pattern should have ensured that the wreck site was surveyed multiple times within each sidescan data set. This was not the case. The reason for this becomes apparent when the position of the Thomas Lawrence is viewed within the context of the surrounding bathymetry. The wreck is located on the side of a large sandwave that may be covering part of the site.
 
From sidescan sonar survey lines to the west of the site, the acoustic energy striking the Thomas Lawrence would have a low angle of incidence and very little energy would be reflected back to the sidescan towfish. Therefore only sidescan sonar survey lines to the east of the site, which would have a high angle of incidence to the site and consequently a large amount of energy, would be reflected back to the towfish producing good images of the wreck.
 
The position of the Thomas Lawrence is such that it is also near the base of the Hastings Shingle Bank and so survey lines oriented E-W, and passing to the north of the wreck site, would not have produced a clear sidescan image. This problem, when combined with the fact that the wreck is partially buried and also has no discernable magnetic signature during this survey, have given the Thomas Lawrence it’s reputation for being very difficult to locate.