Unit 12

1. Read and translate the text

Correction of Charts

General Information

No correction, except those given in Section II of Admiralty Notices to Mariners, Weekly Editions, should be made to any chart in ink.

Corrections to charts from information received from authorities other than the Hydrographic Department may be noted in pencil, but no charted danger should be expunged without the authority of the Hydrographer of the Navy.

All corrections given in Notices to Mariners should be inserted on the charts affected. When they have been completed the numbers of the Notices should be entered clearly and neatly; permanent Notices in waterproof violet ink, Temporary and Preliminary Notices in pencil.

Temporary and Preliminary Notices should be rubbed out as soon as the Notice is received canceling them.

Chart 5011 – Symbols and Abbreviations used on Admiralty Charts should be followed to ensure uniformity of corrections. These symbols are invariably indicated on Overlay Correction Tracings.

If several charts are affected by one Notice, the largest scale chart should be corrected first to appreciate the detail of the correction.

Last Correction

When correcting a chart; first check that the last published correction to it, which is given at the end of the new Notice, has been made to the chart.

Detail required

The amount of detail shown on a chart varies with the scale of the chart. On a large scale chart, for example, full details of all lights and fog signals are shown, but on smaller scales the order of reduction of information is Elevation, Period, Range, until on an ocean chart of the area only lights with a range of 15 miles or more will normally be inserted, and then only their light-star and magenta flare. On the other hand, radio beacons are omitted from large-scale charts where their use would be inappropriate, and, unless they are long-range beacons, from ocean charts.

Notices adding detail to charts indicate how much detail should be added to each chart, but Notices deleting detail do not always make their distinction. If a shortened description would result in ambiguity between adjacent aids, detail should be retained. The insertion of excessive detail not only clutters the chart, but can lead to errors, since the charts quoted as affected in each Notice assume the Mariner has reduced with the scale of the charts the details inserted by previous Notices.

Alterations

Erasures should never be made. Where necessary, detail should be crossed through, or in the case of lines, such as depth contours or limits, crossed with a series of short double strokes, slanting across the line. Typing correction fluids should not be used.

Alterations to depth contours, deletion of depths to make way for detail, etc., are not mentioned in Notices unless they have some navigational significance.

Where tinted depth contours require amendment, the line should be amended, but the tint, which is only intended to draw attention to the line, can usually remain untouched. Where information is displaced for clarity, its proper position should be indicated by a small circle and arrow.

Blocks

Some Notices are accompanied by reproductions of portions of charts (known as “Blocks”). When correcting charts from blocks, the following points should be borne in mind.

• A block may not only indicate the insertion of new information, but also the omission of matter previously shown. The text o the Notice should invariably be read carefully.

• The limiting lines of a block are determined for convenience of reproduction. They need not be strictly adhered to when cutting out for pasting on the chart, provided that the preceding paragraph is taken into consideration.

• Owing to distortion the blocks do not always fit the chart exactly. When pasting a block on a chart, therefore, care should be taken that the more important navigational features fit as closely as possible. This is best done by fitting the block while it is dry and making two or three pencil ticks round the edges for use as fitting marks after the paste is applied to the chart.