Author Topic: Proposed changes to the depiction of latitude and longitude on OS maps  (Read 2678 times)

Hugh Westacott

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This is a copy of  a post on the website of the Charles Close Society for the Study of Ordnance Survey maps. Richard Oliver of Exeter University is generally recognized to be the leading authority on OS maps.

The following has been sent out by Ordnance Survey. In its original form the e-mail includes an attached document, with illustrations, explaining about grids and datums, which would be difficult to forward, and from which I have extracted the following important passage:

"To support the increasing usage of GPS devices, OS are considering options that could help bring digital navigation devices and paper maps closer together and work more in harmony. Such an option could be the changing of the overlay on paper maps from Airy 1830 to WGS84.

Its important for us to stress that this is NOT a change in the base map datum or the National Grid, which remains the Transverse Mercator Projection on the Airy 1830 ellipsoid, but it would result in a change in the datum of the latitude/longitude overlay only, adjusting where the latitude/longitude markers fall on the OS paper maps. For OS Landranger Maps, this movement may be as little as 2mm."

The e-mail originating from OS is as follows:


Proposed changes to the depiction of latitude and longitude representation on paper maps tell us your thoughts

Ordnance Survey GB is considering changing the overlay showing latitude and longitude markers on Ordnance Survey paper maps. This would mean moving towards the overlay showing latitude and longitude used on GPS devices, to help bring digital navigation devices and paper maps closer together and work more in harmony. We believe this would have little impact on the majority of users of our paper maps; however, we would like your opinions on this change to ensure we fully consider all options and impacts before we make a final decision.
Wed like you to read the information below, and, if you would like to share your thoughts on how this would affect you, complete our short survey by Friday 3 October.
or respond directly to the Ordnance Survey product manager:
Please reply to our Product Manager:
Nicola Johnson
Product Manager - Consumer
Ordnance Survey
L1F3, Explorer House
Adanac Drive
SO16 0AS
Tel:         023 8005 5514
Mob:    07825 024176<>

The slight shift in L & L in the margin and on the map face will no doubt be a little irritating for those of us who like visual consistency, but the proposal does not affect the National Grid - a most important consideration for those of us who have large archives of NG references, which would require conversion were WGS84 to be adopted as the basis of the grid. Indeed, I believe that OS did toy with changing the grid to WGS84 about 20 years ago, but took it no further.

Richard Oliver


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