British Geological Survey maps - their characteristics and history

Under construction

Large-scale maps: the six-inch and 1:10,000 series

Introduction

Maps can be grouped into two main series based on the underlying Ordnance Survey base maps onto which the geology is drawn

• County Series
• National Grid series

The formal titles of the map series are:

England and Wales

Geological Survey of England and Wales County Series 1:10560

Geological Survey of England and Wales County Series, New Meridian 1:10560

Isle of Man

Geological Survey of the Isle of Man 1:10560

Scotland

Geological Survey of Scotland County Series 1:10560

Geological Survey of Scotland County Series, New Series 1:10560

Geological Survey of Scotland County Series, New Series, New Meridian 1:10560

National Grid maps [covers the whole of Great Britain]

Geological Survey of Great Britain National Grid Series 1:10560/10000

At the beginning of the Geological Survey the primary mapping was undertaken at one inch to one mile scale. From the 1850s it became the intention that the geological survey of the country would proceed at the six inch to the mile (1:10,560) scale but the chief printed product would continue to be the one inch to one mile (1:63,360) scale geological maps. However, key areas such as the coalfields and London would be formally published as printed sheets at 1:10,560 scale. The majority of 1:10,560 maps remained unpublished and copies were made available for public consultation in the Survey offices.

Note on variability of the collections

It is important to be aware, that the database/catalogue of maps is one of individual physical maps. Each physical map having an entry in the database and with in many cases, an associated scan. For instance, if three copies of the same map were held, one in the three main offices, there will be three entries in the database, and possibly three scans. It is also possible multiple variants to exist for any given sheet number, some sheets may have up to 35 variants. The reasons for variants are many, multiple copies may occur because of:

• Different editions
• Copies held at different Survey office locations
• Copies held at different locations at the same site e.g. a copy held in the Drawing Office, Library, NGRC (Records)
• Copies of early hand coloured printed maps - while they may have the same basic metadata, depending on when they were created they may have had minor changes added. Where this is the case changes are in colour of geological units or even new engraved geological boundaries are can be expected. Changes can be minor and not documented.
• Copies in different states e.g. a Standard (official approved maps), Dyeline master (created for reproduction), Dyeline print (printed for the various Survey offices), hand-coloured dyeline print.
• Copies of Standards that were created to allow manuscript additions to be made without changing the approved and signed Standard. Often called Correction copies, though unapproved ad hoc sheets with additions will also be encountered.
• Later digitally created maps have an Electronic master and Digital Deposit copy (both have slightly different marginal information).

County Series maps

England and Wales

Geological Survey of England and Wales County Series 1:10560

Geological Survey of England and Wales County Series, New Meridian 1:10560

Isle of Man

Geological Survey of the Isle of Man 1:10560

Scotland

Geological Survey of Scotland County Series 1:10560

Geological Survey of Scotland County Series, New Series 1:10560

Geological Survey of Scotland County Series, New Series, New Meridian 1:10560

The standard large scale map for recording field survey information was for much of the Geological Survey's existence, the 1:10,560 or 6 inches to 1 mile Ordnance Survey maps. An O.S. map would be cut up to convenient sized parts for the field mapping. On return to the office the geology would be transferred to a complete County series map, this would then be known, after approval as a 'Standard' or 'Clean copy' in Scotland. The County Series maps are indexed numerically under individual counties. Each county is a sub-series with further sub series depending on the OS base map series used.

Their map projection was related to a central meridian for each county or groups of counties, so each had its own sheet numbering system. For some counties the meridian changed and the OS base maps and subsequent geological maps were issued on different sheetlines and numbering system. The new sheetlines/sheet numbers bear no relation to the sheetlines/sheet numbers of the supeceded series. For some areas users will need to check the different series for their chosen area Checking index maps to ensure coverage and sheet numbers.

The County Series were issued as either 'Full Sheets' and 'Quarter Sheets'—the latter carrying the suffixes NW, NE, SW, and SE—are more recent, the former, full sheets, mainly at earlier periods of production. Over 10,000 sheet areas are covered if all the editions and amended or superseded versions were taken into account there are over 30,000 map sheets.

A considerable number of sheets, particularly in the coalfield counties such as Yorkshire, Lancashire, and Durham were published as monochrome maps (from engraved copper or lithographic plates) and subsequently hand coloured. Sheets for the London area were eventually published and printed in colour. The unpublished maps can appear in many formats, a list of forms is given below.

Gallery of County Series maps

National Grid series maps

National Grid maps [covers the whole of Great Britain]

Geological Survey of Great Britain National Grid Series 1:10560/10000

In the 1960s, the County maps started to be replaced by 6 inches to 1 mile National Grid sheets based on the four quadrants (NW, NE, SW, SE) of a 10 km Ordnance Survey National Grid square. The latter are defined by the 10 km intervals of the larger 100 km square identified by a specific two-letter code. Each map is thus denoted by a unique reference, e.g. SP 29 NW. SP=100 km square; 29=10 km square; NW=5 km square

A considerable number of these were printed lithographically, mostly in monochrome, sometimes called 'lines edition' some were also in colour.

In the late 1970s, conversion to the metric 1:10,000 scale was introduced and became the standard large-scale format for field mapping. Formal publishing was abandoned and replaced by dyeline or photographic processes as a method of reproduction, maps were printed on demand rather than printing and holding stocks. On completion of each sheet, it became customary to prepare a short descriptive report providing notes and local details of the geology for each map sheet area. These were issued as 'open-file' in the Survey Technical Report series.

A very small number of remote areas were mapped at 1:25,000 scale, the subsequent maps are also at 1:25,000 scale and are included in this series.

Areal coverage provided by the National Grid series of large-scale maps is limited in extent and the preceding County series of six-inch maps can still be the most up to date map available for some areas.

Gallery of National Grid series maps:

Key attributes of 1:10,560/1:10000 maps

Geological edition

Solid - later Bedrock geology

Drift - later Superficial geology

Composite (combined Solid and drift/Bedrock/superficial)

The type of approval of the map

The type of approval ranges from Unapproved through to Fully approved (by Assistant Director) for manuscript/unpublished maps. An extra level of approval would be given any sheets that were published and printed.

Published

Fully approved (by Assistant Director)

Lines only approved (by Assistant Director or Regional Geologist)

Regional Geologist approved

Project Leader approved

Unapproved

Survey type

Maps could be the result of the Primary (first) survey or subsequent surveys or revisions. Surveys, revisions etc could be of a full sheet, part sheet geographically or part sheet stratigraphically. An example of the latter is say only the Carboniferous was revised not other geological periods represented on the map.

Area mapped (land area mapped geologically)

All land area mapped — the whole sheet has been mapped

Part of land area mapped — while mapping was undertaken at 1:10,560/1:10000 the standard published output was the 1"/1:50,000, the mapped geology may stop at a 1"/1:50,000 boundary

Up to county boundary — a result of county based sheet lines. The other part could be on a sheet from the other county series.

Dates on maps — The following types of dates may appear on a map:

Survey date/Revision dates: Year or range of dates of survey or resurvey or revisions.

Published date: Year of publication or release of the geological map

Copyright date: This is the year of the geological copyright and must not be confused with the Ordnance Survey topographical copyright year.

Approval date: The Assistant Director’s (AD) approval may be given on a stamp on standards. It should consist of a signature and a date, occasionally it is the signature only. If an AD signature and date is not available but an Regional Geologist’s (RG) signature and date is - then this date is included in this field and an appropriate entry is inserted in the Approval status field (see entry for Approval status field). Only maps with manuscript signatures, physically signed by AD or RG are considered approved. Photocopying and dyeline processes will reproduce the signatures on copies, but this does not infer the copy is an approved map. Some of the Scottish maps have a signature on the reverse of the map and this is obviously not transferred to any copies made from it.

Form — Given the long history of the series, back to the mid 1800s the form of originals, copies etc has varied. The following is a list of forms that will appear in the collection.

Coloured litho

Coloured manuscript

Coloured photograph of coloured litho

Coloured photograph of standard copy

Coloured photograph of standard

Digital deposit copy

Dyeline master

Dyeline print

Electronic (digital) master

Electronic (digital) print

Monochrome photograph

Monochrome photograph of a coloured litho

Monochrome photograph of a coloured manuscript

Monochrome photograph of a manuscript

Monochrome photograph of a standard copy

Monochrome photograph of a standard original

Monochrome photograph of an uncoloured litho

Manuscript

Photographic negative

Published litho

Standard copy

Standard original

Uncoloured litho

Photocopy

Photocopy of a coloured litho

Photocopy of a coloured manuscript

Photocopy of a standard copy

Photocopy of a standard original

Wipe-on

Base material for the maps

Electronically held (digital) information

Photographic negative

Opaque plastic

Paper

Transparent plastic

Map form — The process which has generated the base material for the map:

Dyeline

Electronically held (digital) information

Lithographic

Photographic

Elecrostatic or inkjet plot

Wipe on

Photocopy

Geological information — The way the geological information is portrayed:

Fairdrawn - professionally drawn map - near the level at which a map could be published

Manuscript - hand drawn

Sometimes a map maybe a mix of Fairdrawn and manuscript

Inked geology — The geology inked on a map confers a greater status of permanence and authority

All Inked

Some

Up to county boundary

None

Coloured state of the map — The amount of colouring on a map can vary:

All coloured

Part coloured

Up to county boundary

Uncoloured

Colouring type — Type of colouring on the map:

Toned (printed or electronically produced)

Water coloured - common for the majority of the history of the series

Crayoned

Edged - colour depicted mostly close to a boundary

None

Digital attribution

No digital data

Unattributed map face data

Partly attributed map face data

Fully attributed map face data (the marginalia may also be available)

Status flag

Standard — This is the official approved and signed copy of the geology of an area. In Scotland they were called 'Clean Copy'

Digital Deposit Copy — A paper output of the 'Master' prepared for deposit for public and staff consultation in the BGS offices

Master (dyeline or digital master) — More recently when a sheet was produced digitally, this would be the master file.

Correction copy — After a 'Standard' had been approved and signed, no extra additions to the Standard were allowed. Any new additions were made on a copy of the standard known as the 'Correction copy'. After significant change and after approval a new Standard was created.