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Articles

1978: Vol. LV, No. 2

The Rapid Digitisation of Tide Chart Recrods

Submitted
August 7, 2015
Published
2015-07-09

Abstract

Although tide recording installations are increasingly being provided with punched-tape outputs, the majority of tide recordings have been and still are, for historical, economical or visual reasons, on roll or strip chart paper. Therefore, in the analysis of tide recordings, there is often the need for digitisation of the data, so that computer methods can be employed. Digitisation can be accomplished manually, but the process is laborious and slow even with the aid of electro-static X-Y plotters, and especially so if shorter than hourly time increments are required. The authors encountered the problem recently in a tidal hydraulics study of the Western Solent entailing the installation and maintenance of six autographic recorders — five of the pneumatic type and one having a float well. These recorders were maintained for a minimum period of 1 year, and the requirement was for digitising at 15-minute intervals for subsequent computer analysis of water surface slopes. This required the extraction of some 16 800 data points per month. The paper describes the technique and equipment employed to achieve a rapid and effective digitisation of the recordings, and is thought to be novel with regard to this particular application.