Fundamental Benchmarks FBM (FOI241249)

We received your request on 30/04/2024.

We have handled your request under the Freedom of Information Act (FOIA) 2000.

A copy of your request is set out in the extract below:

“Fundamental Benchmarks (FBM)

Could the OS please provide me with the position information (both horizontal and vertical) for all FBMs (both extant and destroyed).

Can this positioning information be as accurate and precise as available (for example from when the FBMs were integrated into the passive station network in the late 90s / early 2000s or better if available).

For each FBM can the following be provided – FBM Name, FBM reference number, (ETRS89 Cartesian) X, Y, Z, (ETRS89 Geodetic) Latitude, Longitude, Ellipsoid height, (OSGB36 National Grid) Easting, Northing, Height (as per passive station), Height (as per levelling) Ideally latitude and longitude will be provided in the decimal degrees format.

Can the FBM information be supplied in Excel xlsx format or as a comma separated value (CSV) text file). Please also provide any associated or related FBM information that you feel is appropriate”

I confirm that Ordnance Survey does hold some of the information you have requested.

I am pleased to provide you with the Fundamental Benchmarks file (.csv) with regard to your request.

In addition to the attached, OS publishes data for passive stations and FBMs on our website:

• Passive stations (coordinates list) (.txt)
• Passive stations (complete database)(.txt)
• FBM data (.zip)

The data provided to you (the csv. file and the published data) only includes FBMs that were ‘extant’ at the time the data was collected.

We do not hold information for ‘destroyed’ FBMs.

Advice and Assistance

The datasets we hold, as detailed above, were frozen approximately 20 years ago when our OS Net System and OSTN/OSGM transformation models were fully established. Therefore, the datasets do not contain all FBMs that there have ever been since some will have been destroyed and removed from the lists prior to the datasets being frozen. Since the dataset was frozen some may have been destroyed but this will not be reflected in the dataset since it is longer updated as it is a frozen dataset.

For information, our website provides an overview of OS Net: Overview of OS Net (ordnancesurvey.co.uk). OSTN and OSGM are the transformations that link 3D positions measured using GNSS with the national coordinate and height reference systems of Great Britain, Ireland and Northern Ireland.

Information supplied to you in response to an FOI request may be protected by copyright. You are free to use if for your own purposes, including private study and non-commercial research, and for any other purpose authorised by an exception in current copyright law. Documents (except photographs) can be used in the UK without requiring permission for the purposes of news reporting. Any other reuse, for example commercial publication, would require the permission of the copyright holder. Most documents supplied by Ordnance Survey will have been produced within government and will be Crown copyright.