I read with interest the article entitled “Off to see Seabirds” in the Sunday Times Plus of May 2, by Gehan de Silva Wijeyeratne. The author’s comment that “The location and shape of the continental shelf [off Kalpitiya] was a guess until exploration for oil resulted in the first sea depth contour charts in October 2009” is, in my opinion, contestable.
The continental shelf in the Kalpitiya area has been fairly well known for more than half-century. It was surveyed for H.M. Hydrographic Office between 1838 and1944 and has been updated with new data regularly since then. Despite the lack of modern high-tech methods, these surveys resulted in reasonably detailed information on the location, shape and depths of the continental shelf.
No guess work was involved. H.M. Hydrographer of the Navy produced accurate charts (the Admiralty Hydrographic Chart series) from this information. In my opinion these charts are entirely adequate for seabird watching.
I have no doubt that the sea depth contour charts of October 2009, carried out with the latest technology, are very accurate and revealing; but I surmise that, they only supplement and refine rather than replace the Admiralty hydrographic charts.
Rex I. De Silva,
Madapatha |
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