Dataset details: CRDA/26/DS/4

The North Sea GIS 2004 snapshot was transferred to NDAD from the Department of Trade and Industry on 7th January 2005.

This is the 2004 snapshot of the North Sea Geographical Information System (GIS). The North Sea GIS was created by the Oil and Gas Directorate of the Department of Trade and Industry to provide a geophysical and licensing analysis of the United Kingdom's oil and gas exploration. The 2004 dataset contains data relating to onshore and offshore oil, gas and condensate fields in the UK, and data relating to the Irish Republic and foreign sector offshore fields. It also includes data covering current and previous licences, and details of UK pipelines, including those under construction.

North Sea GIS data has been used regularly by such entities as the British Geological Survey, Schlumberger Geoquest and Asset Geoscience Ltd. Other users have included oil companies, central and local government, data supply companies and other national governments. For further information about the North Sea GIS, see the Series Catalogue.

The North Sea GIS 2004 snapshot was received in ESRI (Environmental Systems Research Institute) ArcView shapefile format. It consists of eight spatial datasets: offshore_fields; onshore_fields; offshore_licences; onshore_licences; ukcsquads; median_line, significant_discoveries and bay_closing_lines. Each spatial dataset comprises an ESRI shapefile, consisting of six separate files.

ESRI shapefiles store non-topological geometry and attribute information for the spatial features in a dataset. The geometry for a feature is stored as a shape comprising a set of vector co-ordinates.1 The six files forming the shapefile for each spatial dataset are the main file, index file, dBase file, two spatial index files and a projection metadata file.

The main file has the extension .shp and is a direct access, variable record length file.2 The index file has the extension .shx. Each record in the index file contains the offset of the corresponding main file record from the beginning of the main file.3 The dBase file has the extension .dbf. The dBase file contains feature attributes with one record per feature.4 Each attribute record has a one-to-one relationship with the associated shape record.5 The spatial index files have the extensions .sbn and .sbx. These two files may not exist until you perform theme on theme selection, spatial join, or create an index on a theme's Shape field. If you have write access to the source data directory, the index files will be persistent and remain after your ArcView session is complete. If you do not have write access to the source data directory, they will be removed when you close the project or exit ArcView.6 The projection metadata file has the extension .prj.

The prefix of each file for a spatial dataset is the same, e.g. the files for a spatial dataset called country will be country.shp, country.shx and country.dbf. The full technical description of ESRI shapefiles can be found in the ESRI Shapefile Technical Description.7

The North Sea GIS 2004 snapshot dataset was read into ArcView, version 9. The image of each shapefile was exported to a PostScript format file, which was converted to TIFF using Ghostscript. Non-essential peripheral white-space was then trimmed.

The TIFF image files created from the North Sea GIS are for illustrative purposes only and do not provide the functionality (e.g. layering spatial datasets, spatial joins of areas, etc.) that are possible when using the dataset within ArcView.

The dBase files were read into Microsoft Office Excel 2003 and then exported to CSV format files. These files each contain a number of fields that are automatically generated by the ArcView software. Further details are provided in the associated table catalogues: see Logical structure and schema.

The spatial index files (.sbn and .sbx files) and projection metadata files (.prj) have not been converted. These files hold information that is specific to data manipulation within the ArcView software, and there is no mechanism to export their contents to a non-proprietary format.

Documents relating to the North Sea GIS have been transferred to NDAD. See the Dataset Documentation Catalogue for further details.

There are 8 data tables in this dataset. Eight associated images have been generated by NDAD and catalogued in the Dataset Documentation Catalogue (references CRDA/26/DD/5/2004/1-8). They can also be accessed from their respective table catalogues. Quotations in the 'Scope and content' section of the table catalogues have been taken from the 'readme' files which were transferred with the North Sea GIS data (see the Dataset Documentation Catalogue, reference CRDA/26/DD/3).

The dataset comprises the following table(s):

For preceding datasets in this series, it is understood that data was originally input by means of on-screen forms digitisers using a manually held cursor connected to a PC, to trace over a hard copy image. However, it is not known if the same methods of input and validation were used for the 2004 dataset.

One record in the offshore blocks and licences table (reference CRDA/26/4/3) contains (in the field 'shape_date') an entry that doesn't correspond to the date format for this field. The entry in 'shape_date' for record number 5309 is '2030901'. Other records display 'shape_date' in the format dd/mm/yyyy, i.e. British numeric format. However, '2030901' may be a corruption of '20030901', an ISO date format equivalent to '01/09/2003' which many other records have in the shape_date field.

The six files that comprise one ESRI shapefile were supplied for each of the eight spatial datasets, as expected.

Validation was performed using ArcView version 9 and the NDAD on-line browsing software. For each table, the total number of records in the original dBase (*.dbf) file and the converted CSV (*.csv) file were compared. In all cases these corresponded.

Additionally, a random 53 records were selected from the twelve dBase tables. Each selected record was checked between the original dBase (*.dbf) files and the converted CSV (*.csv) files by ensuring the value of each fields was identical. No discrepancies were noted in any of the 53 records. A random number generator was used to randomly select table and record numbers. The converted GIF image files were compared, by eye, to the original main shape files (.shp) for each spatial dataset. These all appeared to correspond.

1. ESRI Shapefile Technical Description, An ESRI White Paper, ESRI, July 1998, Page 1, available from the ESRI web site.

2. ESRI Shapefile Technical Description, An ESRI White Paper, ESRI, July 1998, Page 2, available from the ESRI web site.

3. ESRI Shapefile Technical Description, An ESRI White Paper, ESRI, July 1998, Page 2, available from the ESRI web site.

4. ESRI Shapefile Technical Description, An ESRI White Paper, ESRI, July 1998, Page 1, available from the ESRI web site.

5. ESRI Shapefile Technical Description, An ESRI White Paper, ESRI, July 1998, Page 1, available from the ESRI web site.

6. File moreinfo.txt sent with data by Oil and Gas Directorate, Department of Trade and Industry. See the Dataset Documentation Catalogue, reference CRDA/26/DD/3/2.

7. File moreinfo.txt sent with data by Oil and Gas Directorate, Department of Trade and Industry. See the Dataset Documentation Catalogue, reference CRDA/26/DD/3/2.