Guidance

Coal outcrops data set: User guide

Updated 15 August 2024

1. Introduction

The Coal Authority manages the effects of past coal mining, including subsidence damage claims which are not the responsibility of licensed coal mine operators. It deals with mine water pollution and other mining legacy issues. It also owns, on behalf of the country, the majority of the coal in Britain, and licenses coal mining.

We use our skills to provide services to other government departments and agencies, local governments and commercial partners. We contribute to the delivery of the UK Government’s Industrial Strategy and the environmental, social and economic priorities of the UK, Scottish and Welsh Governments.

By sharing our knowledge and expertise we support them, and our partners, to create cleaner, greener nations for us all.

Our purpose is to:

• keep people safe and provide peace of mind
• protect and enhance the environment
• use our information and expertise to help people make informed decisions
• create value and minimise cost to the taxpayer

The Coal Authority is an executive non-departmental public body, sponsored by the Department for Energy Security and Net Zero.

Further information on all the digital data available from the Coal Authority.

2. Information about the coal outcrops data set

2.1 Background

The coal outcrops data sets illustrates locations where workable coal seams are present at or close to the surface.

The positions of these coal outcrops have been captured into our geographic information system (GIS) database from published geological information and records held by the Coal Authority or supplied by its predecessors.

2.2 Data set history

The coal outcrops spatial data set was created during the early 1980s in readiness for the automated provision of coal mining reports that was introduced locally in 1985 and established nationally in 1989.

A team of qualified National Coal Board and British Coal Corporation mining surveyors were engaged to rationalise the mining and other source plans, reference the same to Ordnance Survey National Grid  or County Series and subsequently capture the data into the first computerised mining report system. The spatial data sets were subsequently migrated into the Coal Authority’s current ESRI based GIS in 2011.

2.3 Who might require this data set?

This data set is currently used by the Coal Authority in the production of CON29M mining search reports. These provide property specific searches with regard to potential mining hazards in support of the conveyancing market.

This data set is suitable for use by organisations wishing to identify possible ground instability and potential mining hazards. Users may include but are not limited to Local Authorities, infrastructure operators, land developers, home-owners, solicitors, loss adjusters, the insurance industry, architects and surveyors.

2.4 What the data set shows

This layer identifies where an underground coal seam reaches rockhead, indicating coal that may have been worked at some time in the past. Whilst this data set highlights areas of probable underground workings at shallow depth, it may also include areas where the un-viable seams of coal remain.

2.5 Coverage

The coverage of the coal outcrops data set is the known extent of coal mining activity in Great Britain. This area does not represent the full extent of geological coal reserves and resources.

3. Technical information

3.1 Definitions - what does outcrop and seam mean?

Outcrops illustrate a location where a workable coal seam is present at or close to the surface.

Seams are a bed of coal usually thick enough to be profitably mined.

3.2 Accuracy - transfer of information from source plans to the National Coal Mining Database

The Coal Authority’s primary source records are some 120,000 plans of abandoned coal mines for Scotland, England and Wales.  These coal abandonment plans, cover both opencast and deep mining operations, and depict areas of coal extraction and points of entry into the same.

In the late 1970s a national rationalisation project was initiated by the National Coal Board where these abandonment plans, and relevant geological and Ordnance Survey plans were examined to identify unique mining information.

Regional teams of qualified National Coal Board and British Coal Corporation mining surveyors were engaged to rationalise the mining and other source plans and reference the same to National Grid or County Series.

Due to the primitive emerging GIS technology available at the time of initial capture and the primary purpose of the capture being the automated provision of coal mining reports , the rationalised plans show a simplified version of the information contained on the abandoned mine plans.

The mining information contained on these rationalised plans was subsequently digitised by a team of technicians and captured as polygon, point and line data in the Coal Authority’s National Coal Mining Database.

3.3 Source accuracy limitations

All plans are representations and may contain inherent simplifications due to generalisation. When features are represented on plans, their scale often determines the level of detail shown. In addition to these simplifications, limitations may also be introduced through the drawing process.

3.4 Digitisation process accuracy limitations

The digitisation process is likely to have introduced intrinsic limitations due to simplification requirements. As different mining surveyors produced plans with variable levels of detail the Coal Authority’s mining surveyors may have reduced the level of detail contained within the plans in order to produce the digital information.

3.5 Scale

The original plans were produced at varying scales, but were in general digitised to a scale of 1:2500.

3.6 Data Format

The coal outcrops data set has been created as vector polygon data and is available in ESRI File Geodatabase (.gdb) format. Other geospatial formats, including geopackages and CAD can be supplied on request but may incur additional processing costs.

The layer file provided will describe the symbology used by the Coal Authority and has been created using ESRI ArcGIS V10.3.1 Use of any other symbology is not advised for this data set as the symbology used by the Coal Authority is an industry standard and any change of this could significantly affect the perceived understanding.

In order to view the correct symbology the layer file should be loaded in your GIS system.

3.7 Field Descriptions

Data Field	Explanation of Data Field
OBJECTID	OBJECTID File GeoDB ID number
S_OBJECTID[footnote 1]	Source ObjectID Unique Coal Authority ID number
GLOBALID	GLOBALID Globally Unique Identifier (GUID)
DIP_SIDE	Dip Side Dip side equals left or right. Direction of inclination.
CNJCTRD	Conjectured Conjectured indicator equals True or False. Where conjectured indicator equals True then the position is inferred.
SE_CODE	Seam Code A unique alphanumeric identifier used to define a specific seam.
MI_CODE	Mineral Code Mineral worked. Most are coal but we hold records for other minerals on the system in cases where they were worked with the coal or close to the coal seams.
VERIFIED	Verified Verified indicator: True or False. An attribute that determines whether manual intervention is required. Where verified indicator equals False then further information should be sought from the Coal Authority when used in the context of a mining search report, for example CON29M
THICK_DRIFT	THICK_DRIFT Thick drift indicator: True or False. Where thick drift indicator equals True then drift greater than 30m exists at this locality.

3.8 Data update frequency

The Coal Authority is constantly reviewing and updating its data. We therefore make no representation that the coal outcrops data set remains complete, accurate, up-to-date, reliable or exhaustive. Weekly, annual or one-off updates will be provided as per the licence arrangement.

4. Licensing information

The Coal Authority does not sell its digital spatial data to external parties. Instead, it grants external parties a licence to use the data, subject to terms and conditions. In general, a licence fee will be payable based on the type of data, geographic area required, the number of simultaneous users, and the duration (years) of a licence.

All recipients of a licence are required to return a signed licence document to us before authorisation for release of digital data is given.

These are general comments for guidance only. Full details of the terms and conditions of supply are included within licences.

The Coal Authority’s data team will be happy to discuss your proposed use of data and can be contacted at [email protected] .

The data team will usually be able to provide reassurance that the licence will cover individual user requirements or include additional ‘special conditions’ in the licence documentation, addressing specific requirements within the Coal Authority’s permitted usage.

5. Limitations and exclusion of liability

The Coal Authority is committed to ensuring that the digital data it holds and releases to external parties under licence has been through a robust internal approval process to ensure that corporate quality assurance standards are maintained.

This approval process is intended to ensure that all data released:

• is quality assured
• meets agreed data management standards
• is not in breach of any 3rd party intellectual property rights or other contractual issues - such as confidentiality issues

5.1 Limitations

This data set is based on, and limited to, an interpretation of the records in the possession of the Coal Authority at the time the data set was created.

The data set does not categorise the risk of surface collapse and no account is taken of any past remediation that may have been undertaken.

An indication of the presence of a coal mining related feature, such as a mine entry, does not necessarily mean that a location will be affected by ground movement or subsidence. Such an assessment can only be made by inspection of the area by a qualified professional.

If customers are uncertain about the use of particular data they should seek professional advice. However, they may consult the Coal Authority’s data team  on technical matters, licensing arrangements, or general aspects including the appropriateness and limitations of the data.

5.2 Exclusions

The databases comprising the subject matter of this report are made up of information supplied to the Coal Authority by third parties under statutory obligation and of which the Coal Authority has no direct knowledge and has not necessarily had the opportunity to verify. 

Accordingly, it can have no liability for the accuracy of the information comprising the databases or for any loss of whatever nature directly or indirectly caused which may result from any reliance placed upon it. 

The licensee takes the information as provided without any such express or implied warranty and must rely upon its own enquiries and where necessary obtain appropriate insurance against any loss arising.

1. Only available to Coal Authority ‘use licensees’ for inclusion in CON29 mining reports ↩