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Guide reference: Military Records Information 36
Last updated: 4 September 2009

1. What is an Admiralty chart?

Hydrographic charts are maps designed as aids to navigation at sea. The National Archives holds many such charts, including hand-drawn (manuscript) charts as well as printed ones, and foreign charts as well as charts produced in Britain, Section 6 of this research guide describes our holdings of foreign, manuscript and early printed charts.

Admiralty charts are hydrographic charts produced by the British Admiralty. The Hydrographic Office was established as a sub-department of the Admiralty in 1795 and issued its first officially published Admiralty chart in November 1800. Admiralty charts are the most common type of chart among the records held at The National Archives and our holdings of them cover seas and coastal areas in all parts of the world.

Most Admiralty charts delineate the coastline and high and low water marks, and record the depth of water as established from soundings. They record navigational hazards such as reefs and wrecks, and navigational aids, such as lights, buoys and beacons. Most charts have a compass indicator, often an elaborate compass rose. Most also have some indication of scale, either a scale bar or representative fraction, or a border showing degrees of latitude and longitude. Where direct indication of scale is absent, as on older charts, the scale is usually noted in the appropriate published Catalogue of Admiralty Charts, Plans, and Sailing Instructions (available on microfiche in the Map and Large Document Reading Room at The National Archives).

One of the characteristics of an Admiralty chart is that it is continually updated and corrected. Obsolete charts were regarded as dangerous and were to be destroyed because they presented a potential navigational hazard. Dates of survey and compilation are minutely recorded, as are those of the corrections continually made to maintain the accuracy and utility of the chart. These corrections were often made by amending the existing copper plates on which the chart was engraved and re-publishing it as a new edition; in other instances the chart was completely re-drawn. Note, however , that, particularly in the early years of the Hydrographic Office, published Admiralty charts drew on earlier surveys. In extreme cases this means that some charts may be based on surveys made more than a century earlier. For example, Admiralty chart 751, the chart of Maculla Bay which was listed in the first published catalogue of 1825, bears a survey date of 1703.

Some Admiralty charts contain little information on areas inland of the foreshore other than that required to assist in making a landfall. Others include extensive representations of land features, and may also have coastal elevations and topographic views as insets. Nineteenth-century charts in particular may include ground plans of sites of archaeological interest, or details of coastal forts and other defences, as well as pictures of natural features. Some insets contain detailed charts of harbours. Admiralty charts record names given to coastal features and include many names no longer in use today. In many instances they also provide the best and most easily accessible maps of small oceanic islands. Some charts record surveys of navigable rivers.

Initially, Admiralty charts were identified only by means of a title, broadly describing the area covered. Since 1839, each chart has also been assigned a number, printed at the bottom right hand corner of each sheet. The number is now considered to be the prime reference indicator for the chart. Some chart numbers include letter prefixes and suffixes, but note that the prefix AC used in The National Archives card catalogues represents former National Archives practice and does not appear on the chart itself. When charts were redrawn, the chart number could fall vacant and subsequently the same number may have been re-used for a chart of a different title and area. For example, chart 483 has at different times related to a chart of St Jago, in the Cape Verde islands - or to Thursday Island, in the Torres Straits off the north coast of Australia; chart number 695 has similarly been used for the Cook Straits and for Madagascar.

2. Where to find Admiralty charts

The National Archives does not have a discrete collection of Admiralty charts, but numerous Admiralty charts have been identified in the public records, and many more remain as yet undiscovered. Record series containing substantial numbers of charts are listed in section 3, below.

The national record set of Admiralty charts is maintained by the Hydrographic Office, which remains an authorised place of deposit for its own records. It holds an almost complete set of printed Admiralty charts, as well as many related records.

The largest readily accessible collections of Admiralty Charts are held by the map department of the British Library and the other legal deposit libraries. If you require a large number of charts, or specific editions, it is best to use these collections. 

The National Maritime Museum has a large collection of Admiralty charts, and some original surveys. The Royal Geographical Society also holds a significant, but incomplete, collection of Admiralty charts.

3. Admiralty charts in The National Archives

The Admiralty charts in The National Archives are those collected or used by government departments and the armed services in the normal course of administrative or operational functions. They may include editions, states and printed amendments not represented elsewhere, although most are of standard issue. Many charts bear manuscript additions and amendments relating to their use. Individual charts may also accompany correspondence indicating errors and desirable amendments. As well as complete Admiralty charts, the public records include portions cut from whole charts. Military and civilian personnel sometimes traced or copied charts in the course of their duties and examples of these also survive among the records. The following series are known to contain significant numbers of Admiralty charts:

Catalogue reference Description
ADM 1 Admiralty and Secretariat Papers 1660-1976
ADM 7 Admiralty and Secretariat Miscellanea 1563-1953. The case files relating to the search for Sir John Franklin include numerous successive editions of early charts of Arctic America.
ADM 116 Admiralty and Secretariat Cases: 1852-1960
ADM 137 War of 1914-1918: Admiralty Historical Section: Packs and Miscellaneous Records 1860-1925
ADM 199 Admiralty: War History Cases and Papers: 1939-1956
ADM 231 Admiralty: Naval Intelligence Reports 1883-1965. Charts illustrating reports on foreign naval strength, coastal defences, etc.
CAB 11 Committee of Imperial Defence: Colonial/Overseas Defence Committee: Defence Schemes 1863-1939. Charts illustrating memoranda and instructions to Colonial Governors and officers commanding, concerning schemes for local defence, port regulations, etc.
CO 700 Colonial Office: Maps and Plans: Series I 1595-1927
CO 1047 Colonial Office: Maps and Plans: Series II 1779-1947
CO 1054 Colonial Office: Maps and Plans: Post -1940 Collection 1897-1984. Includes items which accrued in the Foreign Office after 1940.
FO 925 Foreign Office: Maps and Plans: 1700-1940
WO 32 War Office: Registered Files: General Series: 1845-1985
WO 78 War Office: Maps and Plans: 1627-1953. Include numerous Admiralty charts annotated to show the location and effectiveness of coastal defences.
WO 192 Fort Record Books: 1892-1957. Many of the books that relate to coastal forts contain Admiralty Charts.

In addition many Admiralty station records, ships' logs, Colonial Office and Foreign Office original correspondence series, and Embassy and Consular archives are known to contain Admiralty charts.

The surviving original artwork for the views and sketches of coasts and rivers that appear on many Admiralty charts is held as a discrete collection in series ADM 344

4. Finding a particular chart at The National Archives

Increasing numbers of Admiralty charts are described in detail in Discovery, our catalogue, and can be searched by keywords. Other charts are currently only accessible via other forms of description. Some are described fully in topographically-arranged printed catalogues or supplementary card catalogues. Others are listed more briefly in the Summary Calendar of uncatalogued maps and indexed in its subject indexes under the heading 'Charts: Admiralty'.

There are also two specialised means of reference: a card index arranged in chart number order and microfiche copies of various editions of the published Catalogue of Admiralty Charts, Plans, and Sailing Instructions issued by the Hydrographic Department periodically from 1825, and annually from 1886 (hereafter called the Admiralty Chart Catalogue). All of these additional finding aids are available in the Map and Large Document Reading Room.

None of these finding aids are fully comprehensive. Many charts have never been described individually and it is likely that considerable numbers of them remain to be discovered within ships' logs, Admiralty station records, and a wide range of other public and private documents now held by The National Archives.

4.1 Starting with a known chart number

Where individual charts are fully described in our catalogue, this description normally includes the chart number in the form Admiralty chart [number]. Descriptions of tracings or copies of charts also include the number of the original published chart, where this is known.

The numerical card index to British Admiralty charts includes many charts not yet described on our catalogue. It provides a brief indication of the geographical area covered by each chart and The National Archives document reference used to order it. The numerical card index does not give dates of survey, publication or revision and does not include partial charts, tracings or copies. Because of the Admiralty's habit of re-using numbers, remember to check that the area indicated on the card index corresponds to the area you require. The card index is also cross-referenced to paragraph numbers in the published catalogues Maps and Plans in the Public Record Office , volume 2: America and West Indies [AM] and volume 3: Africa [AF or AFR], which provide fuller descriptions of the charts. A similar index to charts described in the published catalogue Maps and Plans in the Public Record Office , volume 4: Europe and Turkey is included within the volume.

The subject index volumes of the Summary Calendar of Maps and Plans contain lists of charts arranged in chart number order under the heading 'Charts: Admiralty'. These include some charts not yet listed in the published catalogues, card index or our catalogue.

4.2 Starting with a place name or geographical area

Those Admiralty charts described in our catalogue can also be found by searching directly for place names, for example Australia AND chart AND Admiralty. This will also pick up some tracings, portions of charts and records relating to charts, where these have been catalogued in detail. Chart titles are more likely to contain relatively broad place designations (such as 'English Channel'), than the names of individual towns or other features. You can also restrict the search by date for greater precision.

The printed catalogues and supplementary catalogues contain descriptions of charts alongside those of other kinds of maps and are arranged topographically, making searches by geographical area relatively straightforward.

4.3 Using the Admiralty Chart Catalogue

The microfiche copies of the Admiralty Chart Catalogue provide a comprehensive listing of the charts that have been published by the Hydrographic Office. You can use a combination of the geographically-arranged area listings, place name indexes, and index maps to find the chart that you require. The appearance of a particular chart in the Admiralty Chart Catalogues does not necessarily mean that The National Archives has a copy, but you can use the chart numbers and descriptions supplied to search our own catalogue more effectively. Knowing a chart's number and title also makes it easier to find in another institution's collections if we do not hold a copy.

The format of individual Admiralty Chart Catalogues has varied over time, but all are sub-divided into broad geographical areas. From 1832, these areas are also identified in a list of contents at the beginning of each volume, and thus appear within the first few frames of each set of microfiche. Over time, the broad areas have been sub-divided further. The charts are listed within each area in a sequence that may reflect geographical logic or chart number, but is not alphabetical. Note that in some cases the Admiralty Chart Catalogue shows a shelf number (where the charts were stored in the Hydrographic Office) as well as the chart number: take care not to confuse the two numbers.

Before 1839, Admiralty charts were not numbered. If you have found your chart title in an earlier Admiralty Chart Catalogue, you will need to use the geographical headings and descriptions in the 1839 Catalogue as a guide to repeat your search and so determine the chart number. Some charts published by the Hydrographic Office between 1800 and 1838 were completely withdrawn before the issue of the 1839 Catalogue and were never assigned chart numbers. These can only be searched for in The National Archives' own catalogues by title or place name.

Most volumes of the Admiralty Chart Catalogue also contain an index of place names which are cited within the chart title but are not the principal 'filing point'. The index gives the page numbers within the geographical area listings on which the place name appears. The Catalogues also include indexes or cross-references arranged by chart number.

From 1911 onwards, the Admiralty Chart Catalogues also contain index maps (sometimes known as graphic indexes). Initially, the primary means of reference used to determine each particular chart number remained the citation of the chart title within the geographical area listings, but from about 1950 the Catalogues rely far more heavily on these index maps for this purpose. The area shown on each chart is indicated by straight lines drawn on a base map and the chart number appears at one corner of the area so delimited. The accompanying text gives the precise title of the chart, and the scale to which the chart is drawn as well as publication and edition dates. Graphic indexes dating from after the Second World War are particularly useful for checking whether a place or area not explicitly mentioned in a chart title is covered by a particular numbered chart.

4.4 Other methods of searching

Where charts are described in detail in our catalogue, the descriptions normally include scales and the names of individual surveyors. Speculative searches of records, both within the series noted in section 3 of this research guide and elsewhere, may reveal previously unrecorded charts, as well as records relating to their creation or use

5. Copperplates of Admiralty charts

The National Archives has one example of a copperplate of a British Admiralty Chart: number 2657 'Japan. South Coast of Honshu. Gulf of Tokyo or Yedo' (1881, corrected to 1948) in MPZ 1/22.

The microfiche set of Admiralty Chart Catalogues includes a separate catalogue of copper plates. These plates were formerly held by the Hydrographic Office and six of them can still be seen there. The other plates have been deposited in appropriate national institutions, including the National Maritime Museum and the British Library. The largest portion of the plates (including the surviving plates by Dalrymple and Horsburgh) were presented to the Admiralty Library, which also keeps a list of all the plates and their custodians.

6. Manuscript charts, early printed charts and foreign charts

Early hydrographic charts included medieval portalans and manuscript pilot books. Only one example of a medieval portolan has so far been identified at The National Archives: MPB 1/38, showing the eastern Mediterranean and part of the Black Sea.

By the seventeenth century, printed charts and pilot books were being published commercially. Many printed charts of seventeenth and eighteenth century date are found among The National Archives' holdings both as individual sheets and in atlas form. Individual sheets within a bound atlas or pilot are often not individually catalogued, and the atlases, catalogued under country, continent or world headings, must be searched speculatively. Series known to contain early printed charts include: the State Paper Office Map Collection (SP 112), War Office Map Library (WO 78), Admiralty Miscellanea (ADM 7), and the library classes of atlases ZMAP 2 and ZMAP 3.

Naval officers and other seamen continued to draw charts by hand into modern times. The record series of Hydrographic Department original surveys (ADM 352) contains many manuscript charts dating from the 18th and 19th centuries. Published Admiralty charts were largely based on surveys such as these. Charts were very often drawn by hand in ships' logs and journals; for instance, the records of voyages of exploration (including those of Captains Cook and Bligh) in ADM 55 include many charts.

The public records also contain numerous examples of hydrographic charts produced by nations other than Great Britain. Many of these foreign charts are described individually in our catalogue, published catalogues or supplementary catalogues, but there are no specific indexes to them. As with Admiralty charts, many early and foreign charts, both manuscript and printed, remain to be discovered within the records. Please tell us if you find a previously unrecorded chart.

7. Further reading

The following recommended publications are available in The National Archives' Library.

Vice-Admiral Sir Archibald Day, The Admiralty hydrographic service 1795-1919 (HMSO, 1967)

Rear-Admiral GS Ritchie, The Admiralty chart: British naval hydrography in the nineteenth century (1967, new edition 1995)

Admiralty manual of hydrographic surveying (HMSO, 1938)

M Chriss and GR Hayes, An introduction to charts and their use (third edition, 1964)

Derek Howse and Michael Sanderson, The sea chart: An historical survey based on the collections of the National Maritime Museum (1973)

AHW Robinson, Marine cartography in Britain: A history of the sea chart to 1855 (1962)

Peter Whitfield, The charting of the oceans: Ten centuries of maritime maps (1996)

Guide reference: Military Records Information 36

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