Hydrographic Note

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For instructions, see below.

INSTRUCTIONS

1. Mariners are requested to notify LINZ Hydrographic Services, National Office, Land Information New Zealand, Private Box 5501, Wellington, New Zealand, when new or suspected dangers to navigation are discovered, changes observed in aids to navigation, or corrections to publications seem to be necessary. The Mariners Handbook (NP 100), Chapter 8, gives general instructions.
2. This form and its instructions have been designed to help both the sender and the recipient. It should be used, or followed, closely whenever appropriate. Copies of this form may be obtained gratis from LINZ Hydrographic Services at the address above, or in PDF format directly from the LINZ website at www.linz.govt.nz
3. When a position is defined by sextant angles or bearings (true or magnetic being specified) more than two should be used in order to provide a check. Distances observed by radar should be quoted. However, when there is a series of fixes along a ship's course, only the method of fixing and the objects used need to be indicated. Latitude and longitude should only be used specifically to position the details when they have been fixed by astronomical observations or GPS. A full description of the method, equipment and datum used should be given.
4. A cutting from the largest scale paper chart is the best medium for forwarding details. The alterations and additions should be shown thereon in red ink. When requested, a new copy will be sent in replacement of a chart that has been used to forward information, or when extensive observations have involved defacement of the observer's chart. If it is preferred to show the amendments on a tracing of the largest scale chart (rather than the chart itself) these should be marked in red ink as above, but adequate detail from the chart must be traced in black ink to enable the amendments to be fitted correctly.
5. The Mariners Handbook (NP 100) should be consulted when soundings are obtained. The echo sounding trace should be marked with times, depths, etc., and forwarded with the report. It is important to state whether the echo sounder is set to register depths below the surface, or below the keel; in the latter case the vessel's draught should be given. Time and date should be given in order that corrections for the height of the tide may be made where necessary. The make, name, and type of echo sounder set should also be given.
6. Modern echo sounders frequently record greater depths than the set's nominal range, (e.g. with a set whose maximum is 500m, a trace appearing at 50m may in fact be 550m or even 1,050m). Erroneous deep soundings beyond the sets nominal range can usually be recognised by the following:
   1. The trace being weaker than normal for the depth registered
   2. The trace appearing to pass through the transmission line
   3. The "feathery" nature of the trace.
7. Reports which cannot be confirmed or are lacking in certain details should not be withheld. Shortcomings should be stressed and any firm expectation of being able to check the information on a succeeding voyage should be mentioned.
8. Reports of shoal soundings, uncharted dangers and navigational aids out of order should, at the mariner's discretion, also be made by radio to the nearest coast radio station. The draught of modern tankers is such that any uncharted depth under 30 metres or 15 fathoms may be of sufficient importance to justify a radio message.

NOTE: An acknowledgement of receipt will be sent and the information then used to the best advantage, which may mean immediate action or inclusion in a revision in due course. When a Notices to Mariners is issued, the sender's ship or name is quoted as authority unless (as sometimes happens) the information is also received in a foreign Notices to Mariners. An explanation of the use of contributions from all parts of the world would be too greater task and a further communication should only be expected when the information is of outstanding value or has unusual features.