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Field measurements

Request for information – FOI16725

Request

Thank you for your letter of 17 November 2016, which was received on 21 November and referred to me from our Customer Services Centre. In your letter, you confirmed that you request the following enquiry to be dealt with by Ordnance Survey in accordance with the Freedom of Information Act (FOIA) 2000:

It would be of great assistance if your office could confirm that the field measurement of .74 acre (.299 ha) includes the ‘pink’ area of land [by reference to the plan enclosed with your letter to Ordnance Survey of 20 October 2016]; and/or that otherwise the coloured land forms or has historically formed part of field XXXX, within the Lodge (formerly XXXXX XXXX) holdings.

Our response

I can confirm that Ordnance Survey does not hold any information on whether or not the field measurement of .74 acre (.299 ha) includes the ‘pink’ area of land; and/or that otherwise the coloured land forms or has historically formed part of field XXXX, within the Lodge (formerly XXXXX XXXX) holdings.

Ordnance Survey does not hold records of surveyor’s notes, or the reasons why there were changes to specific physical features on the maps. The published data itself forms the record.

Section 16
Under our duty to provide advice and assistance as stipulated in Section 16 of the FOIA, we can provide the following explanation which may assist you in this matter.

The measurement of 0.74 acres is only valid for the 1882 map (field no. XXXX). Although this measurement is also stated on the fields in question on the 1907 (field no XXXX) and 1986 maps (field no XXXX), this measurement is inaccurate because the field itself has changed shape each time the map was updated. Between 1882 and 1907 the river changes shape, between 1907 and 1986 the upper right boundary has changed which means that the value of 0.74 is only valid for the original map and not the subsequent ones.

We are unable to use GIS software accurately to verify whether or not the 0.74 acreage measurement includes the pink area of land, and/or that otherwise the coloured land forms or has historically formed part of field XXXX.

This is because there is an inherent margin of error that arises when historical maps are measured using GIS software. Ordnance Survey historical maps were created on a county meridian and the modern maps were created on the national grid. When the historical maps are converted to digital form using GIS, the ‘re-projection’ of the maps from county meridian to national grid creates a ‘squashing’ or ‘stretching’ effect that means there is an inherent error margin in the measurement.

Having said the above, we refer you to three maps, dated 1882, 1907 and 1986, that are enclosed (PDFs) with this letter. We used GIS software to calculate the following measurements of the fields using the physical boundaries highlighted in red or pink on the enclosed maps.

Our results are as follow:

  • 1882: field excluding the buildings neighbouring the pink area of land (pink dashed line): 0.289 ha
  • 1882: field including the buildings neighbouring the pink area of land (dark pink solid line): 0.298 ha
  • 1907: field including the buildings neighbouring the pink area of land: 0.282 ha
  • 1986: field including the buildings neighbouring the pink area of land: 0.264 ha

You will note we have calculated the area for the field (including the buildings neighbouring the pink area of land) from the 1882 map as 0.298 ha, which is equivalent to c. 0.74 acres. However, you should bear in mind that (i) this calculation is based on a survey from 1882 and it is not unreasonable to expect an error margin in such survey, and (ii) there is also an error margin from re-projection of historical mapping into digital format, as explained above. These two factors combined mean that we cannot confidently state that the 0.74 acres calculated for the 1882 field boundaries (including the buildings neighbouring the pink area of land) necessarily included the area highlighted in pink on the map.

Please note that the enclosed Ordnance Survey maps are protected by Crown copyright and database rights. Therefore, you may not reproduce, distribute or publish it without Ordnance Survey’s express permission. This restriction does not apply to reasonable use for your own non-commercial research purposes, private study or any other uses permitted under the Copyright, Designs and Patents Act 1988.

Internal review

Your enquiry has been processed according to the Freedom of Information Act (FOIA) 2000. If you are unhappy with our response, you may request an internal review with our FOI Internal Review Officer, by contacting them as follows:

FOI Internal Review Officer
Customer Service Centre
Ordnance Survey
Adanac Drive
Southampton
SO16 0AS

Email: foi@os.uk

Please include the reference number above. You may request an internal review where you believe Ordnance Survey has:

  • Failed to respond to your request within the time limits (normally 20 working days)
  • Failed to tell you whether or not we hold the information
  • Failed to provide the information you have requested
  • Failed to explain the reasons for refusing a request
  • Failed to correctly apply an exemption or exception

The FOI Internal Review Officer will not have been involved in the original decision. They will conduct an independent internal review and will inform you of the outcome of the review normally within 20 working days, but exceptionally within 40 working days, in line with the Information Commissioner’s guidance.

The FOI Internal Review Officer will either: uphold the original decision, provide an additional explanation of the exemption/s applied or release further information, if it is considered appropriate to do so.

Appeal to Information Commissioner's Office (ICO)
If, following the outcome of the internal review you remain unhappy with our response, you may raise an appeal with the Information Commissioner’s Office at:

The Case Reception Unit
Customer Service Team
The Information Commissioner’s Office
Wycliffe House
Water Lane
Wilmslow
Cheshire
SK9 5AF

Email: mail@ico.gsi.gov.uk

Telephone helpline: 0303 123 1113 or 01625 545745 for advice, Monday to Friday.

Thank you for your enquiry.

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