International Bathymetric Chart of the Central Eastern Atlantic

The International Bathymetric Chart of the Central Eastern Atlantic (IBCEA) is a continuation and further development of the General Bathymetric Chart of the Oceans (GEBCO), under the general guidance of the IOC Consultative Group on Ocean Mapping (CGOM). This chart is prepared and published with the cooperation of volunteer hydrographic Offices and/or groups of scientists from appropriate institutions.

The Editorial Board of IBCEA was established by Resolution of the Fourteenth Session of the IOC Assembly for the purpose of technical direction of its compilation and publication.

Sheets for IBCEA will be portrayed with Mercator Projection using WGS-84 reference ellipsoid.

A scale of 1:1,000,000, using the 20N as a reference parallel..

A scaled border of each sheet shall be shown subdivided into one minute increments of latitude and longitude.

Meridians and parallels shall be drawn every two degrees (even values).

Labeling of the graticule shall be every one degree.

D.

The Tropic of Cancer shall be shown..

The neat line size of each sheet shall not exceed 750 x 1100 mm, so as to allow printing on an A0 size paper sheet.

A.

For each chart a consecutive sheet number shall be used as shown in the Assembly Diagram.

Sheet numbers shall be printed in 8 mm Arabic figures in the lower right-hand and top left-hand corners of each sheet.

The date of the chart publication to be shown on each sheet shall be the date of the end of compilation.

Depths and topographic heights shall be shown in meters. Depths should be corrected from the last edition of the Echo-Sounding Correction Tables, published by the United Kingdom Hydrographic Department, and this should be stated on the face of the chart.

All marginal information shall be in English, or bilingual in English and another language.

This shall include:

1.

The general title of the chart.

2.

Sheet number.

3.

Projection, ellipsoid and scale (see 201, 202).

4.

Unit of measurement used for depths and heights.

5.

Code of colors used to portray hypsometry.

6.

Code of color used to portray bathymetry.

7.

An index of areas and names of countries whose Hydrographic Offices or groups of scientists prepared plotting sheets for the sheet.

8.

The names of the scientific coordinators of the chart series and of the scientists responsible for the scientific content of the sheet.

9.

The logo of the Intergovernmental Oceanographic Commission (IOC) of Unesco.

10.

Edition number and date of publication (see 206) followed by the statement : "Published by the....(name of printer) under the authority of the IOC (of Unesco)".

11.

List of the sources of the data used.

For the land area, topographic maps shall be used.

The best available agreed upon coastline shall be used. The coastline shall be shown as a firm line in black.

A.

Contours on land shall be at 200 m intervals.

B.

The thicker lines shall be at 200, 1000, 2000, 3000 etc. m intervals.

C.

Additional contours which may be required by the data must be shown.

D.

A color change for hypsometry shall be used at the following intervals : 0-200, 200-1000, 1000-2000, etc., m.

E.

The significant heights shall be shown.

The chart shall include :

1.

Rivers and channels ;

2.

Lakes ;

3.

Lagoons.

Major Cities and towns shall be included with priority given to those on the coast.

A.

A sparse pattern of numerical soundings shall be shown to indicate maximum and minimum (and other significant) depths, where known, over major undersea features in such a way as not to detract from the paramount objective of indicating sea floor relief by means of contours.

B.

The exact position of all numerical soundings shown shall be indicated by a dot. The depth shall be written as cartographically convenient against the dot using 1.5 mm sans-serif figures. Where space does not permit the juxtaposition of the figures they may be offset and linked by a fine line to the dot placed in the exact position.

C.

Actual data control will be shown as data representing continuously sounded traverses, possibly printed on the reverse side of the paper. Areas of detailed surveys where sounding lines are closely spaced may be delineated using numbered boxes which are referenced in the margin.

A.

Basic contours shall be at 200 m intervals.

B.

The 200 m contour line and all contours at 1000 m intervals shall be drawn using thick lines.

C.

20, 50 and 100 m contours, as well as intermediate 100 m contours, if necessary, shall be drawn using thin lines.

D.

A color change for the bathymetry shall be used at the following intervals in meters: 0-200, 200-1000, 1000-2000, 2000-3000, etc.

A Digital chart should be prepared at the same time as or before conventional printed charts.

A.

A proposed list of names for inclusion on each sheet will be submitted by Chief Editor for approval to the GEBCO Sub-Committee on Geographic Names and Nomenclature of Ocean Bottom Features. In preparing this list account should be taken of the guidelines contained in the IHO-IOC publication P-006 "Standardization of Undersea Feature Names". Names already in use, referring to the GEBCO Gazetteer, will be accorded preference, with new names being given only to previously unnamed features.

B.

As a general policy, local names (cities, towns, mountain ranges, rivers, etc.) shall be in exact agreement with the form prescribed by the most authoritative national source. However, in those cases where the national names differ substantially from the normal English usage, the English version shall be shown alongside in parenthesis.

C.

The nomenclature for undersea features shall be shown in the English language.

1.

For plotting and contouring purposes the British Admiralty’s plotting sheets for oceanic soundings should be utilized.

2.

Soundings should be in meters corrected using the last edition of the "Echo-Sounding Correction Tables".

3.

The position of the sounding should be the central point of the group of figures representing it. But the position may also be indicated by a dot with the sounding figure alongside, and if necessary, by a thin line drawn to connect the two.

4.

The sounding figures should be inscribed across the track; the figures should be easily readable, the recommended average size being 1.5 - 2 mm in height.

5.

The largest possible number of soundings should be shown on the plotting sheets so long as their clarity is not impaired. When soundings are very dense, the number may be reduced if care is taken not to eliminate the more important soundings : maxima and/or minima.

6.

The margin of each plotting sheet should contain the following legend:

"Compiled by....."

"Last brought up to date on....."

"Prepared under IOC (International Bathymetric Chart of the Central Eastern Atlantic)".

7.

Each plotting sheet should be accompanied by two overlays:

A.

Overlay contour lines with contouring made through each 100 meters, additional contours may be drawn through 50 and 10 meters, where arranged (on the shelf and abyssal plains) ;

B.

Overlay source materials on which should be shown the following:

- Areas of soundings and position of isolated soundings with the appropriate legends required to indicate the source and date of such soundings;

- Information on the navigation method and its precision;

- Information on the type of echo-sounder and its precision.

8.

On each plotting sheet and overlay, the date of completion of compilation should be indicated.