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OS Net free services

We offer two key free services for professional surveyors, geodesists and GIS developers:

We also provide a range of other resources, including, background information and legacy horizontal and vertical survey control information.

The National GPS Network

The Ordnance Survey National GPS Network is the infrastructure that gives access to our national coordinate systems in Great Britain: ETRS89; OSGB36® National Grid; and Ordnance Datum Newlyn (ODN).

The National GPS Network has taken over this role from our traditional control networks of triangulation stations and levelled bench marks. These traditional control networks are no longer maintained by OS and will eventually be phased out.

The national coordinate systems are used by many different user groups in a variety of ways:

  • ETRS89, a precise version of the GPS coordinate system WGS84, is the standard coordinate system for precise GPS positioning throughout Europe.
  • OSGB36 National Grid is the national standard coordinate system for topographic mapping, including all OS mapping, and for geographically referencing many kinds of information in relation to OS mapping.
  • ODN is the national standard coordinate system for measuring height above mean sea level. ODN is the usual definition of mean sea level in mapping and engineering in Great Britain.

The National GPS Network makes accurately determining these national standard coordinates much easier and more efficient for land surveyors, compared with traditional (pre-GPS) surveying methods. It is now possible to determine precise ETRS89 coordinates for your GPS control stations with a single GPS receiver, without ever leaving the survey site. 

Since these coordinates can be instantly and precisely transformed to OSGB36, National Grid and ODN height coordinates  – or to a project-specific mapping grid if appropriate – you can use precise national coordinates for a greater range of mapping, engineering and environmental projects than was previously possible. In future, as a result, many spatial datasets created at various times, by various organisations, for various reasons, will be directly and precisely compatible with each other.

Active Station RINEX Data

OS Net comprises over 100 continuously operating GNSS reference stations spread over the whole of Great Britain. You can download precise GPS data from these stations within 90 minutes of the time of observation. By processing this with your own GPS data, you can obtain precise ETRS89 coordinates of your survey stations.

Typical users will have at least one dual-frequency survey grade GPS receiver and post-processing software.

RINEX data is now available from over 100 Active OS Net stations across Great Britain.

Coordinate transformer

This facility allows you to precisely transform between ETRS89, GPS derived, coordinates and Ordnance Survey National Grid coordinates and heights above mean sea level (Ordnance Datum Newlyn for mainland Britain). Ordnance Survey map coordinates and heights can therefore be derived for any GPS position in Great Britain through a precise transformation.

For GI software developers, there is a free precise solution to the GPS/Ordnance Survey coordinate discrepancy problem.

Legacy control databases

These databases enable free access to several control datasets that are no longer updated:

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For general enquiries, complaints, feedback or suggestions, email: customerservices@ordnancesurvey.co.uk or call us on 08456 05 05 05