OR/16/046 Technical information
| Armstrong, R, Daley, D, Lawley, R, Myers, A and Smith, A. 2016. User guide for the BGS geology: 50k dataset (v8). British Geological Survey Internal Report, OR/16/046. |
Definitions
BGS geology: 50k
The BGS geology: 50k v8 dataset is BGS’s primary national geological reference dataset. It is compiled from individual digital tiles of data which were based on the traditional ‘one-inch to one-mile’ and 1:50 000 scale, paper geological maps; with each one typically covering an area of 20 x 29 km (12 x 18 miles). Distance units reflect the original paper map coverages. Digital scans of these paper maps are mostly available through the online BGS map portal (www.bgs.ac.uk/data/maps/home.html).
The geology is generalised from more detailed field-surveyed maps (typically between 1:10 000 and 1:25 000 scales) and it is the most extensive, moderately-detailed, geological interpretation available from BGS for onshore Great Britain. It is used to create other BGS products such as GeoSure and BGS Civils.
BGS Geology: 50k does not include geological information such as Generalised Vertical Sections or cross-sections. These can be viewed on the original scans, but the user needs to be aware that the classification and nomenclature of geological units may differ from the original paper map. Topographical base maps are not included with BGS Geology: 50k data.
Themes and layers
For this product there are 4 geological themes relating to: Bedrock lithologies, Superficial deposits, Mass movement deposits and Artificial deposits. The data is supplied as 5 or more GIS layers; there is one layer per geological theme and an additional layer supplied to cover linear features (which contains information relevant to the bedrock and superficial themes as well as topographic landforms).
Scale
BGS Geology: 50k is designed for use at approximately 1:50 000 scale.
Data description
The BGS Geology: 50k V8 dataset is provided as five GIS map layers. It is recommended that the layers are displayed in the following order within GIS (to allow best visualisation and clarity of the map objects):
Users should be aware that some layers are intrinsically related to each other, for example, the Faults features from the Linear layer are directly relevant to the Bedrock theme/layer; and the Mass-Movement theme/layer should be assessed in conjunction with the Superficial and Bedrock layers.
Field descriptions
Each geological theme (GIS map layer) contains a series of attribute fields. Attribution is specific to the theme/layer, for example, bedrock objects are attributed with lithostratigraphy, whereas geological faults (in the linear layer) are not. The following tables indicate the attributes available in each theme/layer. BGS aims to provide a balance between built-in content, web- delivered content as well as the potential for ‘add-on’ information/dictionaries.
This version of BGS Geology: 50k has different attribute content compared with previous releases. Further details about the changes are given in Data history.
Attribution fields for the bedrock and superficial themes
The Bedrock and Superficial themes concern areas of geological materials and are typically attributed with descriptions for their name, age (expressed in multiple ways) and their lithology. The nomenclature for age and lithology are held in the BGS Lexicon of Named Rock Units (www.bgs.ac.uk/Lexicon/), and the BGS Rock Classification Scheme guides (www.bgs.ac.uk/bgsrcs/details.html).
The information fields attached to polygons (at attribute level 24) in these two themes are explained in Table 1 below.
| Data Field | Explanation of Data Field | Note | |
| LEX_WEB | Direct hyperlink to the definition of the particular geological unit in the BGS Lexicon of Named Rock Units (BGS website): e.g. www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=GOG |
Note 1 | |
| LEX | A single Lexicon (or LEX) computer code used to identify the rock unit(s) or deposit(s) as listed in the BGS Lexicon of Named Rock Units: e.g. GOG | Note 2 | |
| LEX_D | A description of the LEX code above, giving the full name of the unit(s): e.g. GREAT OOLITE GROUP is the full name of the unit coded as GOG | ||
| LEX_RCS | The primary two-part, LEX & RCS, code used to label the geological units in BGS Geology data: e.g. GOG-LMST | Note 3 | |
| RCS | A rock-classification code of up to 6 characters (mostly letters) forming the second part of the primary LEX_RCS attribute. e.g. MDCO. The code can represent a single lithology or multiple lithology’s (see RCS_X) | Note 4 | |
| RCS_X | A variant of the RCS code (above) which individually lists the components of heterolithic units: e.g. MDST + [CONG] (shown as RCS = MDCO). Subordinate units are denoted in [ ] brackets | Note 5 | |
| RCS_D | Description of the RCS code(s) above giving the lithology of the unit: e.g. MUDSTONE AND [SUBEQUAL/SUBORDINATE] CONGLOMERATE is the description of the rock coded as MDST + [CONG] | ||
| RCS_ORIGIN | An attribute of the RCS code(s) above, classifying the mode of origin of the lithology of the rock/deposit: e.g. Sedimentary, Igneous, and Metamorphic | Note 6 New | |
| RANK | Rank of the unit in the lithostratigraphical or lithodemic hierarchy: e.g. BED or SUITE | Note 7 | |
| BED_EQ_D | Description of the Bed or equivalent lexicon code for the unit where applicable | ||
| MB_EQ_D | Description of the Member or equivalent lexicon code for the unit where applicable | ||
| FM_EQ_D | Description of the Formation or equivalent lexicon code for the unit where applicable | ||
| SUBGP_EQ_D | Description of the Sub-Group or equivalent lexicon code for the unit where applicable | ||
| GP_EQ_D | Description of the Group or equivalent lexicon code for the unit where applicable | ||
| SUPGP_EQ_D | Description of the Super-Group or equivalent lexicon code for the unit where applicable | ||
| MAX_TIME_Y | Maximum age (in years), of the oldest time division in which the geological unit was formed: e.g. 170300000 | Note 8 | |
| MIN_TIME_Y | Minimum age (in years), of the youngest time division in which the geological unit was formed: e.g. 163500000 | ||
| MAX_AGE | Maximum age defined for the unit e.g. ASBIAN | Note 9 | |
| MAX_EPOCH | Maximum epoch defined for the unit: e.g. VISEAN | ||
| MAX_SUBPER | Maximum sub-period defined for the unit: e.g. MISSISSIPPIAN | ||
| MAX_ PERIOD | Maximum period defined for the unit e.g. CARBONIFEROUS | ||
| MAX_ERA | Maximum era defined for the unit e.g. PALAEOZOIC | ||
| MAX_EON | Maximum eon defined for the unit e.g. PROTEROZOIC | ||
| BGSTYPE | The BGS Geology theme: e.g. BEDROCK, SUPERFICIAL | ||
| LEX_RCS_I | A computer code that can be used to sort units into approximately the correct stratigraphical order (by Period). NB it does not completely resolve UK stratigraphy and must NOT be used as a substitute for determining full stratigraphical relationships between units. | ||
| LEX_RCS_D | A full description of the LEX_RCS above: e.g. GREAT OOLITE GROUP — LIMESTONE | ||
| BGSREF | A BGS code used to define the colour for the polygon based on the LEX_RCS code pair. Colour information can now be applied from ‘add on’ tables in a variety of ways, please see Appendix 4 | ||
| MAP_SRC | Name of the digital geological tile (number and name based on published map sheet) that the polygon appears on: e.g. EW075_PRESTON, SC084E_NAIRN where prefix ‘EW’ is for England & Wales and ‘SC’ for Scotland | Note 10 New | |
| MAP_WEB | The MAP_WEB link provides a direct hyperlink to the appropriate, original, paper maps held in the BGS Map Portal www.bgs.ac.uk/data/maps/home.html | Note 11 New | |
| OS_TILE | Ordnance Survey 5 km tile identifier. This is used to enable BGS Geology products to be updated in 5km tiles and allow integration into best-available scale maps (only available in the variant Ordnance Survey (OS) 5 km tiled version of the dataset) | New | |
| VERSION | Version number and attribute level of the digital data: e.g. 8.24 is version 8, with attribute level 24 | ||
| RELEASED | Date the BGS Geology data files were created by BGS: e.g. 28-07-2016 | ||
| NOM_SCALE | Nominal scale of the published (or compiled) information used to prepare the digital data: e.g. 50000 for 1:50 000 [including 1:63 360 and 1:100 000 maps] (see limitations section below) | ||
| NOM_BGS_YR | The year date of publication of the most up-to-date map sheet, or the date of publication in BGS Geology: 50k (if no map previously exists). Where not known or inappropriate, field is null |
||
| UUID | Universally Unique Identification that can be used to identify individual features: e.g. bgsn:DM50_V8_digmap1004081046355357 | ||
| Fields in GREEN are derived from the BGS Lexicon | Fields in BLUE are derived from the BGS Rock Classification Scheme | ||
| Fields in PURPLE are derived from the BGS Geological timechart | Fields in brown are for metadata purposes | ||
| Note 1 | The LEX_WEB link provides a hyperlink to the online Lexicon resource. The online version is updated regularly. | ||
| Note 2 | The Lex attribute is the computer code linking to the BGS Lexicon (database of named rock units) www.bgs.ac.uk/lexicon/home.cfm.The Lexicon code may refer to a single identifiable unit or a package of units where the individual components cannot be differentiated. | ||
| Note 3 | The BGS Geology dataset uses the LEX_RCS codes as a primary key, which can be used to JOIN (append) ‘add-on’ datasets | ||
| Note 4 | The RCS attribute is the computer code linking to the BGS Rock Classification Scheme (RCS) www.bgs.ac.uk/bgsrcs/home.html The field may include abbreviated codes for multiple lithologies | ||
| Note 5 | The RCS_X field provides a list of individual RCS lithology codes that make up the overall lithological description of the unit. The suffix _X was added to distinguish this listing of the components from the abbreviated code now shown in the RCS field. | ||
| Note 6 | The origin of each rock/deposit type has been introduced in version 8, this is in part to assist users who wanted to know some fundamental properties of the geological materials (see future revisions section below). | ||
| Note 7 | The parentage of each rock/deposit is provided in these fields and these are all derived from the BGS LEXICON. The ‘RANK’ of a unit identifies the units position within a hierarchy eg a ‘bed’ may be part of a named member, which is itself part of a formation, several formations may make up a group and several groups may form a supergroup. The BED, MEMBER, FORMATION, SUBGRP GROUP and SUPGRP codes/names describe the ascending parentage for each unit (other non-stratigraphic schema are also shown in this way). A formation is the fundamental lithostratoigraphical unit and is the prime mapping-unit for BGS and need not be divided up into named members or beds; nor does a formation have to belong to a group or supergroup. ‘NotAp’ is the abbreviation for ‘Not Applicable’ and is used to indicate that it is not appropriate to list child units of lower rank; ‘NoPar’ is the abbreviation for ‘No Parent’ and is used to indicate that no parental unit of higher rank has been identified. Users are recommended to refer to the LEX_WEB link to find the latest information concerning the lithostratigraphy of a unit. All codes and names used in V8 are correct at time of publication. | ||
| Note 8 | These figures give an indication of the maximum age range (in years before present) of the lithostratigraphical units as given in the BGS Geological Timechart available at: www.bgs.ac.uk/downloads/browse.cfm?sec=8&cat=39 (where they are expressed as ‘million years’). Some of these values are interpolations; the +/- error ranges are not provided here. The age range given is that for the time period ascribed to each geological unit in the BGS Lexicon. They do not give absolute age measurements made on the individual geological units (see future revisions section below). | ||
| Note 9 | The maximum geochronological age (expressed as age/stage/chron, epoch, sub-period, period, era or eon) for each rock/deposit is provided in these fields. These are all derived from the BGS Lexicon and Geological Timechart. ‘NOT DEFINED’ is used to indicate that no age classification has been identified (or is needed). Users are recommended to refer to the LEX_WEB link to find the latest information concerning the lithostratigraphy of a unit. Some geological units straddle more than one geological age.
All codes and names used in V8 are correct at time of publication. | ||
| Note 10 | This attribute was previously called SHEET. It has been changed in Version 8 to MAP_SRC, to reflect that BGS Geology is no longer just compiled from published map sheets, but from a range of sources. | ||
| Note 11 | The MAP_WEB link provides a hyperlink to any online resource that acts as reference material for BGS Geology content. Currently, the weblink will take users to the appropriate, original, paper maps held in the BGS Map Portal www.bgs.ac.uk/data/maps/home.html (future versions will hyperlink to other resources). | ||
Attribution fields for mass movement and artificial themes (GIS Layers)
The Mass Movement and Artificial themes concern areas of geological materials and are typically attributed with descriptions for their lithology and some limited information about their age. The information fields attached to polygons in these themes are explained in Table 2 below.
| Data Field | Explanation of Data Field | Note | |
| LEX_WEB | Direct hyperlink to the definition of the particular geological unit in the BGS Lexicon of Named Rock Units (BGS website): e.g. www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=WMGR | Note 1 Table 1 | |
| LEX | A single Lexicon (or LEX) computer code used to identify the rock unit(s) or deposit(s) as listed in the BGS Lexicon of Named Rock Units: e.g. WMGR | Note 2 Table 1 | |
| LEX_D | A description of the LEX code above, giving the full name of the unit(s): e.g. WORKED AND MADE GROUND is the full name of the unit coded as WMGR | ||
| LEX_RCS | The primary two-part, LEX & RCS, code used to label the geological units in BGS Geology data: e.g. WMGR-ARTDP | Note 3 Table 1 | |
| RCS | A rock-classification code of up to 6 characters (mostly letters) forming the second part of the primary LEX_RCS attribute. e.g. ARTDP. The code can represent a single lithology or multiple lithology’s (see RCS_X) | Note 4 Table 1 | |
| RCS_X | A variant of the RCS code which individually lists the components of heterolithic units if appropriate: e.g. MUDSTONE + SANDSTONE (which would be coded as RCS = STMD). Subordinate units are denoted in [ ] brackets. | Note 5 Table 1 | |
| RCS_D | Description of the RCS code(s) above giving the lithology of the unit: e.g. ARTIFICIAL DEPOSITS is the description of the rock coded as ARTDP | ||
| RCS_ORIGIN | An attribute of the RCS code(s) above, classifying the mode of origin of the lithology of the rock/deposit: e.g. Sedimentary | Note 6 Table 1 | |
| RANK | Rank of the unit in the lithostratigraphical or lithodemic hierarchy: e.g. LITHO-MORPHO-GENETIC (a classification by lithology, form or mode of origin, as applicable to such materials) | Note 7 Table 1 | |
| MAX_TIME_Y | Maximum age (in years), of the oldest time division in which the geological unit was formed: e.g. 2588000 | Note 8 Table 1 | |
| MIN_TIME_Y | Minimum age (in years), of the youngest time division in which the geological unit was formed: e.g. 11000 | ||
| MAX_EPOCH | Maximum epoch defined for the unit: e.g. HOLOCENE (Artificial Materials are defined exclusively as Holocene) | Note 9 Table 1 | |
| MAX_ PERIOD | Maximum period defined for the unit e.g. QUATERNARY | ||
| BGSTYPE | The BGS Geology theme: e.g. ARTIFICIAL, MASS MOVEMENT | ||
| LEX_RCS_I | A computer code that can be used to sort units into approximately the correct stratigraphical order (by Period). NB it does not completely resolve UK stratigraphy and must NOT be used as a substitute for determining full stratigraphical relationships between units. | ||
| LEX_RCS_D | A full description of the LEX_RCS above: e.g. WORKED AND MADE GROUND — ARTIFICIAL DEPOSITS | ||
| MAP_SRC | Name of the digital geological tile (number and name based on published map sheet) that the polygon appears on: e.g. EW075_PRESTON, SC084E_NAIRN where prefix ‘EW’ is for England & Wales and ‘SC’ for Scotland | Note 10 Table 1 | |
| MAP_WEB | The MAP_WEB link provides a direct hyperlink to the appropriate, original, paper maps held in the BGS Map Portal www.bgs.ac.uk/data/maps/home.html | Note 11 Table 1 | |
| OS_TILE | Ordnance Survey 5 km tile identifier. This is used to enable BGS Geology products to be updated in 5 km tiles and allow integration into best-available scale maps (only available in the variant OS 5 km tiled version of the dataset) | ||
| VERSION | Version number and attribute level of the digital data: e.g. 8.24 is version 8, with attribute level 24 | ||
| RELEASED | Date the BGS Geology data files were created by BGS: e.g. 28-07-2016 | ||
| NOM_SCALE | Nominal scale of the published (or compiled) information used to prepare the digital data: e.g. 50000 for 1:50 000 [including 1:63 360 and 1:100 000 maps] (see limitations section below) | ||
| NOM_BGS_YR | The year date of publication of the most up-to-date map sheet, or the date of publication in BGS Geology: 50k (if no map previously exists). Where not known or inappropriate, field is null | ||
| UUID | Universally Unique Identification that can be used to identify individual features: e.g. bgsn:DM50_V8_digmap1004081046355357 | ||
| Fields in GREEN are derived from the BGS Lexicon | Fields in BLUE are derived from the BGS Rock Classification Scheme | ||
| Fields in PURPLE are derived from the BGS Geological timechart | Fields in brown are for metadata purposes | ||
Data structure and attribution fields for the Linear Layer
BGS Geology: 50k includes a linear layer to portray geological concepts that are normally depicted in linear form e.g. natural lineation (features that are naturally lines, rather than polygons), intersections of surfaces/planes (that form a ‘line’ in 3D space) and cartographic/geologic generalisations of thin polygons (best represented as a ‘line’ at some scales).
The Linear layer is typically supplied as a single GIS layer, comprising specific categories of line feature (see Table 3 below). BGS can supply the separate categories of linear features on request.
| Category | Description |
| FAULT | Lines representing planes of structural movement such as: normal faulting or thrusts. Relevant to the Bedrock theme. |
| MINERAL_VEIN | Lines representing the surface expression of mineralised fractures/veins Relevant to the Bedrock theme. |
| FOLD_AXIS | Lines representing planes of structural change/symmetry such as: anticline or syncline Relevant to the Bedrock theme. |
| ALTERATION_AREA | Lines that represent the spatial limit of alteration e.g. metamorphic aureoles or vein swarms. Relevant to the Bedrock theme. |
| ROCK | Lines representing thin beds of notable geological materials e.g. Coal, gypsum, ironstone Relevant to the Bedrock theme. |
| FOSSIL_HORIZON | Lines representing surfaces/beds of fossil zonation e.g. marine bands or fish beds Relevant to the Bedrock theme. |
| LANDFORM | Lines that represent landform features e.g. dune crestline or channel margin Relevant to all themes and topography. |
Attribution fields for the linear layer
The Linear layer is attributed to describe the various parameters associated with the 7 categories. Attribution is specific to each subcategory. For example, the Rock and Fossil Horizon categories of the Linear layer concern geological materials and are typically attributed with descriptions for their lithology and age (as per the Bedrock theme); whilst the Fault category may be attributed with a name or hanging-wall notation. Therefore, only some attribute fields are relevant to each category (and are irrelevant to others). Table 4 below, indicates the attributes available.
| Data Field | Explanation of Data Field | Note | |
| CATEGORY | Geological unit category e.g. ROCK, FOSSIL_HORIZON | ||
| FEATURE | The type of line feature/geological feature, in coded and abbreviated form, e.g. Coal_seam_Obs; Ironstone_bed_Inf | ||
| FEATURE_D | Full description of the type of line feature e.g. Coal seam, observed; Ironstone bed, inferred | ||
| LEX_WEB | Direct hyperlink to the definition of the particular geological unit in the BGS Lexicon of Named Rock Units ( BGS website): e.g. www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=AGMB | Note 1 Table 1 | |
| LEX | A single Lexicon (or LEX) computer code used to identify the rock unit(s) or deposit(s) as listed in the BGS Lexicon of Named Rock Units: e.g. AGMB | Note 2 Table 1 | |
| LEX_D | A description of the LEX code above, giving the full name of the unit(s): e.g. Aegiranum Marine Band is the full name of the unit coded as AGMB | ||
| LEX_RCS | The primary two-part, LEX & RCS, code used to label the geological units in BGS Geology data: e.g. AGMB-MDST For this layer, the LEX-RCS code acts as a secondary key to the FEATURE_D description of the line | Note 3 Table 1 | |
| RCS | A rock-classification code of up to 6 characters (mostly letters) forming the second part of the primary LEX_RCS attribute. e.g. MDCO. The code can represent a single lithology or multiple lithology’s (see RCS_X) | Note 4 Table 1 | |
| RCS_X | A variant of the RCS code (above) which individually lists the components of heterolithic units: e.g. MDST + [CONG] (shown as RCS = MDCO). Subordinate units are denoted in [] brackets | Note 5 Table 1 | |
| RCS_D | Description of the RCS code(s) above giving the lithology of the unit: e.g. MUDSTONE AND [SUBEQUAL/SUBORDINATE] CONGLOMERATE is the description of the rock coded as MDST + [CONG] | ||
| RCS_ORIGIN | An attribute of the RCS code(s) above, classifying the mode of origin of the lithology of the rock/deposit: e.g. Sedimentary, Igneous, Metamorphic | Note 6 Table 1 | |
| RANK | Rank of the unit in the lithostratigraphical or lithodemic hierarchy: e.g. BED or SUITE | Note 7 Table 1 | |
| BED_EQ_D | Description of the Bed or equivalent lexicon code for the unit where applicable | ||
| MB_EQ_D | Description of the Member or equivalent lexicon code for the unit where applicable | ||
| FM_EQ_D | Description of the Formation or equivalent lexicon code for the unit where applicable | ||
| SUBGP_EQ_D | Description of the Sub-Group or equivalent lexicon code for the unit where applicable | ||
| GP_EQ_D | Description of the Group or equivalent lexicon code for the unit where applicable | ||
| SUPGP_EQ_D | Description of the Super-Group or equivalent lexicon code for the unit where applicable | ||
| MAX_TIME_Y | Maximum age (in years), of the oldest time division in which the geological unit was formed: e.g. 170300000 | Note 8 Table 1 | |
| MIN_TIME_Y | Minimum age (in years), of the youngest time division in which the geological unit was formed: e.g. 163500000 | ||
| MAX_EPOCH | Maximum epoch defined for the unit: e.g. VISEAN | Note 9 Table 1 | |
| MAX_ PERIOD | Maximum period defined for the unit e.g. CARBONIFEROUS | ||
| BGSTYPE | The BGS Geology theme: e.g. LINEAR | ||
| LEX_RCS_I | A computer code that can be used to sort units into approximately the correct stratigraphical order (by Period). NB it does not completely resolve UK stratigraphy and must NOT be used as a substitute for determining full stratigraphical relationships between units. | ||
| LEX_RCS_D | A full description of the LEX_RCS above: e.g. GREAT OOLITE GROUP - LIMESTONE | ||
| BGSREF | A BGS code used to define the colour for the LEX_RCS code pair. Colour information can now be applied from ‘add on’ tables in a variety of ways, please see Appendix 4 | ||
| FLTNAME_D | The name of the fault if available: e.g. Highland Boundary Fault | ||
| HWALL_ROSE | Indicates the side of the fault that is the “Hanging wall”. The side is depicted as a octant on a compass rose: (North, North east, East, South east, South, South west, West, North West) e.g. East indicates the hanging wall is on the eastern side of the fault trace; Faults yet to be characterised are shown as ‘not-assessed’ | ||
| MINERAL_D | The name of the primary mineral identified, if available: e.g. GYPSUM | ||
| MAP_SRC | Name of the digital geological tile (number and name based on published map sheet) that the polygon appears on: e.g. EW075_PRESTON, SC084E_nairn where prefix ‘EW’ is for England & Wales and ‘SC’ for Scotland | Note 10 Table 1 | |
| MAP_WEB | The MAP_WEB link provides a direct hyperlink to the appropriate, original, paper maps held in the BGS Map Portal www.bgs.ac.uk/data/maps/home.html | Note 11 Table 1 | |
| OS_TILE | Ordnance Survey 5km tile identifier. This is used to enable BGS Geology products to be updated in 5 km tiles and allow integration into best-available scale maps (only available in the variant OS 5 km tiled version of the dataset) | ||
| VERSION | Version number and attribute level of the digital data: e.g. 8.24 is version 8, with attribute level 24 | ||
| RELEASED | Date the BGS Geology data files were created by BGS: e.g. 28-07-2016 | ||
| NOM_SCALE | Nominal scale of the published (or compiled) information used to prepare the digital data: e.g. 50000 for 1:50 000 [including 1:63 360 and 1:100 000 maps] (see limitations section below). | ||
| NOM_BGS_YR | The year date of publication of the most up-to-date map sheet, or the date of publication in BGS Geology: 50k (if no map previously exists). Where not known or inappropriate, field is null | ||
| UUID | Universally Unique Identification that can be used to identify individual features: e.g. bgsn:DM50_V8_digmap1004081050156465 | ||
| Fields in GREEN are derived from the BGS Lexicon | Fields in BLUE are derived from the BGS Rock Classification Scheme | ||
| Fields in PURPLE are derived from the BGS Geological timechart | Fields in brown are for metadata purposes | ||
How the dataset was created
BGS Geology: 50k is a compilation of digital map tiles made by BGS from previously published paper maps at 1:50 000 or 1:63 360 scale (and some 1:100 000 scale data for Orkney and the Western Isles in Scotland). It includes additional survey and archive data (various ages and scales) derived from ongoing survey activities. Previous paper maps are now available online at the BGS Map Portal (www.bgs.ac.uk/data/maps/home.html), an appropriate hyperlink (the MAP_SRC field) is provided in BGS Geology: 50k V8 for each map object to guide the user to the most likely source(s) of archive map material.
Each object in BGS Geology: 50k is attributed with a LEX_RCS identifier or Category/Feature type as explained in Tables 1 to 4.
The digital data may now differ from the original paper maps for a number of reasons, for example: digital data is often modified to improve the fit between source datasets; nomenclature is updated to approved new/revised stratigraphical schemes; errors on printed maps are corrected; and new geological interpretations are made as part of BGS’ remit to provide geological advice to the public and government.
Data history
This is Version 8 of the data (attribute level 24). It incorporates new and revised tiles of data, OS opendata coastline and miscellaneous corrections to features across the country.
Locations of geological map modifications as a result of mapping, modelling or new evidence are shown in Appendix 2 and include new mapping from the following geological sheets:
EW049 Kirkby Lonsdale
EW084 Wigan
EW118 Nefyn
EW125 Derby
EW147 Aylsham
EW266 Marlborough
EW330, 331, 344, 345 Isle of Wight
SC046e Killin bedrock edition
SC046w Crianlarich bedrock edition
SC051e_052w North Mull and Ardnamurchan SC054e Loch Rannoch bedrock edition
SC074e Aviemore superficial edition
SC084e Nairn superficial edition
SC108w Ben Hee
SC102w Oykel Bridge superficial edition
There have been areas of data refinement associated with coastal areas (to incorporate the OS Open Data™ coastline, as well as for near-shore data around the Rivers Dee, Mersey and Thames. Mapping in the vicinity of the proposed High Speed 2 Rail link (London to Birmingham), has also been improved.
BGS Geology: 50k v8 incorporates over 130 000 edits since v7.22. The distribution of map-face changes are shown in Appendix 2. The underlying databases include updates to the BGS Lexicon (in terms of British stratigraphy and age/epoch/period time scales).
The attribute tables have been modified to include:
- a new field for RCS_ORIGIN (e.g. Sedimentary, Igneous, Metamorphic)
- a new field for hyperlinks to the BGS Map Portal
- a new optional field for OS 5 km tile identification (when data is supplied in 5 km tiles)
- a new field (Linear layer) for identifying Fault Hanging Wall orientation
- a changed field for map source (MAP_SRC), Field was formerly called ‘SHEET’
The database has also been restructured slightly so that field lengths are reduced where possible to reduce file size, improve performance on older PC’s, and improve translation outcomes when converting between different file formats.
Deprecated attribute fields
This version of BGS Geology: 50k has different attribute content compared with previous releases. Several fields within previous releases of BGS Geology: 50k contained data better delivered by web content; or via ‘add on’ datasets.
The deprecated (discontinued) fields include the following:
RCS_WEB, BED_EQ, MB_EQ, FM_EQ, SUBGP_EQ, GP_EQ, SUPGP_EQ, MAX_INDEX, MIN_INDEX, MIN_AGE, MIN_EPOCH, PREV_NAME, MIN_PERIOD, MIN_ERA, MIN_EON, MIN_SUBPER, BGSREF_LEX, BGSREF_FM, BGSREF_GP, BGSREF_RK.
These fields have been deprecated because they generally represent ‘codes’ (requiring further user computation) and/or use web-enabled content that is already available within the dataset via the LEX_WEB field.
All deprecated attributes are now supplied as a separate ‘add-on’ reference dataset (in ascii CSV format). These ‘add on’ attributes can be easily reapplied to BGS Geology: 50k V8 if users need them. There is further information relating to how to use ‘add-on’ content in Appendix 4.
Coverage
Data availability at 1:50 000 scale is shown in Appendix 3.
The BGS Geology: 50k dataset covers almost the whole of England, Wales and Scotland. In Version 8 there is now only one map tile with no data on any theme: EW180_Knighton.
Where there is no cover for a theme at 1:50 000 scale, smaller scale 1:250 000 (Bedrock) or 1:625 000 (Bedrock and Superficial) data are available.
Data format
The data are typically released in ESRI Arc® shape file formats. Other formats such as MapInfo TAB are available on request. Both these formats are usable in free applications such as QGIS.
The 1:50 000 scale digital geological data typically comprises four polygon themes: Bedrock, Superficial, Mass Movement and Artificial as well as a Linear layer for faults, thin rock beds such as coals, and landforms.
Limitations
BGS Geology: 50k is a compilation of digital tiles derived from previously published and unpublished maps and archive information. The mapping, description and classification of rocks are based upon the interpretations and evidence available at the time of survey, or time of re-evaluation for modifications/correction. The BGS Geology: 50k dataset therefore represents data of different vintages and origins. This means that it may not always agree with more recently gathered observation (such as boreholes) and that adjacent geological sheets/tiles (of different survey vintages) may not seamlessly fit together spatially, or in terms of lithological description (resulting in some map-sheet ‘edges’ that exhibit contrasting colours/attribution).
The original geological map interpretations were fitted to Ordnance Survey topographical bases available at the time of survey. The digital geological data do not necessarily fit other topographical bases including more modern Ordnance Survey ones.
The 1:50 000 scale digital map data is generalised and the geological interpretation should be used only as a guide to the geology at a local level, not as a site-specific geological plan based on detailed site investigations. The scale of the data is indicated by the nominal scale attribute (NOM_SCALE: 50000) embedded in the data. Do not over-enlarge the data; for example, do not use 1:50 000 nominal scale data at 1:10 000 working scale. If more-detailed information is required then the 1:10 000 scale maps or digital data, which provide the most-detailed interpretations available, should be consulted.
The cartographic accuracy is nominally 1 mm which equates to 50 m on the ground at 1:50 000 scale. This is only a measure of how faithfully the lines are captured; it is not a measure of the accuracy of the geological interpretation.
Your use of any information provided by the British Geological Survey (‘BGS’) is at your own risk. Neither BGS nor the Natural Environment Research Council gives any warranty, condition or representation as to the quality, accuracy or completeness of the information or its suitability for any use or purpose. All implied conditions relating to the quality or suitability of the information, and all liabilities arising from the supply of the information (including any liability arising in negligence) are excluded to the fullest extent permitted by law.
No advice or information given by BGS, NERC or their respective employees or authorised agents shall create a warranty, condition or representation as to the quality, accuracy or completeness of the information or its suitability for any use or purpose.
Future development
This version (v8) has introduced some changes to the structure of the BGS Geology: 50k dataset. This is to allow additional capabilities in future versions as well as facilitate and test the next generation of geological data products. The following section outlines proposed future development of the BGS Geology range of products:
Multiscale mapping (best available scales): These are maps that use the highest resolution of mapping available. Typically this will be a combination of 1:10 000, 1:25 000 and 1:50 000 scales. Maps will be provided in 5 km tiles aligned to the Ordnance Survey 5 km national grid system (v8 has been modified to enable data to be supplied in 5 km tiles and as part of a multiscale system).
Change-only updates: BGS Geology: 50k is normally released episodically as a version- controlled product. It is intended that future users will be able to check for, and incorporate ‘change-only’ updates to digital map data (full version-controlled updates will still be maintained).
Additional attribution: BGS Geology: 50k underpins many other digital map products. It is intended that users will be able to add additional attribute content for new themes (eg Geochemistry, Engineering). Some new content will be free, some may require additional licencing. The additional attribution can be added to the dataset via a database ‘join’ on a primary key (e.g. LEX-RCS or UID fields). Future attribute sets include improved provenance/reference materials, geochemical statistics and improved lithological descriptions. The Add-on datasets in Appendix 4 are examples of how additional attribution will be applied.
Inspire compliance and metadata: A dedicated metadata theme is being developed for BGS Geology: 50k; this theme will also include INSPIRE-compliant content. An additional add-on dataset will include INSPIRE-compliant descriptions of rock/deposits as well as content normally used for BGS Geology: 50k based web-map services (WMS).
BGS is undertaking a review of BGS Geology content (covering aspects of scale, completeness, structural data content and presentation, marginalia, further attribution and delivery/publication option), your thoughts and suggestions on how we can improve BGS Geology are welcomed.
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