Navigation and Seamanship (1+1)

1.4.3. Preparation of charts

Charts are produced by the Hydrographic Department of the Admiralty, British, under the hydrographer of the navy who is responsible not only for the preparation, correction, issue of charts and other navigational publication, but also for the surveying works.

In the later years of the 19^th century other nations began to undertake their own coastal surveying. In addition a great local details comes from bodies such as harbour authorities and other public or private corporation. From the original data thus obtained the charts are schemed and produced ready for the engravers by the specialist staff of the chart Branch. Projections are computed and all important points are plotted accurately before the actual drawing of the chart begins. In India Hydrograhaphic Department of Indian Navy based at DheraDun is responsible for printing and publishing of charts.

This drawing is very accurately engraved on a copper plate by coating it with wax by using special ink on the drawing. The engraving of this copper plate is transferred to a lithographic stone or a zinc plate by contact or by photolithography. The plate is then ready for printing on paper, which is done by lithography or multi coloured offset printing. The paper used is high grade non-distortion paper.

Every new chart in its final proof stage is examined by the officers of the Department responsible as Radio and Telegraph information, wrecks, Lights, Tides and currents etc. It is then examined by the senior officers of the Department, being finally closely inspected by the Hydrographer whose signed approval is necessary before any chart can be published. After the chart is published and distributed, it must be kept up-to-date by incorporating any changes or corrections, which may have occurred subsequently. Such corrections and changes in charts of various parts of the world are issued as “Notices to Mariners” by the Hydrographic Department.