Proposed changes to latitude and longitude representation on paper maps – tell us your thoughts

We’re 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.

We’d 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.

Most people use OS paper maps for location – either they want to know where they are, or where they want to get to (or even where they’ve just been). Once you have an OS paper map in front of you, there are a couple of ways of identifying the location you’re after – you can use National Grid, or latitude and longitude.

Most countries will define a ‘grid’ that can be overlaid onto a map of their country to help determine location. In Great Britain, the National Grid is the map reference system used on all Ordnance Survey maps to identify the position of any feature. The National Grid breaks Great Britain down into progressively smaller squares identified first by letters and then numbers.           lat-long-1

Latitude is generally understood as your position in relation to the equator, which is 0o, and the distances you might be north or south of that line. Longitude is generally understood as your position in relation to the ‘Prime Meridian’, which for Great Britain (and much of the rest of the world) is sited at the Royal Observatory, Greenwich. This is also 0o.                                 lat-long-2

Each of these methods will help you to pinpoint and find a location on a map.

To make life a little more complicated, the Earth is not a perfect sphere – it’s a bit squashed at the poles, so it bulges around the equator (like a Satsuma) – this shape is called ‘ellipsoid’. This can impact on how location is calculated; various interpretations have developed as geographers adapt latitude and longitude calculations to best fit the ‘ellipsoid’ in their part of the world – these are ‘datums’.

Ordnance Survey’s work in Great Britain uses the “Airy 1830 ellipsoid” to underpin the representation of latitude and longitude on OS paper maps, as this best fits Britain. However, in recent years, more and more map users are starting to use GPS devices, which operate on a datum with a wider geographical reach than just Great Britain. The datum that underpins GPS is called WGS84, and through sheer volume of usage is starting to become the default datum.

To support this 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.

It’s 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.


We realise that this is an important change to how our paper maps are presented, so we want to find out what the impact of implementing this change might be to you, the users of OS paper maps. The link below takes you through to a short survey of seven questions – please complete the survey and let us know how this might affect you if we were to move ahead with this change. The survey window closes Friday 3 October 2014, so please send your thoughts to us before then.

Complete the survey: https://response.questback.com/ordnancesurvey/vc4rqrghun/

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21 Responses

    1. Hi David

      Sorry to hear that you’ve been having problems accessing the survey. I’ve just checked and both links to the survey in the article seem to be working – if it still isn’t working for you, could you let us know what device and browser you’re using so that we can look into it further?

      Thanks, Gemma

  1. I have sent my feedback, and I think that this is a bad idea. Rather than offer one or the offer, you should offer the map in both formats, and make clear the inaccuracy introduced by the WGS84 datum due to plate drift. If I measure the coordinates of my house on a BNG map, those coordinates will never change, however with GPS those coordinates will change over time due to plate drift.

    1. Hi Chris

      Thanks for sending in your feedback, the team will be reviewing all of the opinions captured in the survey before making a final decision.

      Thanks, Gemma

  2. Tim

    Interesting question. As a walker for many years (including before GPSs existed), I can say I’ve only ever looked at the grid lines, never the lat/longs on the side of the map.

    Most GPS devices I use (including my phone) can give you the coordinates in lat/long, OSGB, in fact just about any system you like. So I wonder how many people actually use the lat/longs printed on the side of the map any more (surely you’d just ask your GPS to give you OSGB instead?).

    So, maybe the important question now is about digital maps – when a GPS calculates my position, I want the point it draws on the map to match my actual position as closely as possible. Anything that makes this better is probably a good thing. Though, I suspect that the difference this change will make is far less than the accuracy of most GPS, so I wonder if we’ll ever actually notice it.

  3. Kaled


    Not sure the 5mm a year that continental drift introduces will make a difference on a 1:25000 scale map and a 10 m GPS position . But still interesting that this is brought up as an issue. Must be a few more geeks out there like me !

  4. Sounds sensible Gemma

    Something that bridges the digital and print divide is good news for us as we look to a future where these two media get more and more integrated.

    Keep it up!

  5. Mike Parslow

    Any chance of this blog AND the questionnaire in plain English? I got confused over the various ways. National Grid is well known as the transporter of electricity not the OS sytem.

    What attempts are you making to solicit the opinions of the various walking and rambling clubs, Wildlife trusts and Archeological groups who make regular use of the “National Grid” to notify members and the public of meeting places etc. 2mm may be the minimum but what is the max? on the ground I guess this could mean up to 1/4 mile – far enough to cause major problem with neighbouring landowners.

    1. Hi Mike

      We’ve been using the term for a bit longer than they have! The National Grid would not be changing in this update, only the additional markings around the edge of the paper maps (normally in blue) showing the latitude and longitude. If you only use Grid References then you will not notice any change.

      Most GPS devices sold for the UK market can actually show both Airy 1830 and WGS84, but as WGS84 is the default we decided to look at the option of using this on our paper maps. Of course, individual GPS manufacturers that use our maps in their devices have been allowing for this to ensure the map on screen lines up as accurately as possible.

      If you feel there are any organisations that would be affected and would like to respond, please feel free to forward a link to the blog or survey to them.

      1. Hi Jonathan,
        Thanks for the update on this. I must admit the first time that I glanced at this article, I did wonder whether the National Grid lines were being affected by this proposal too. I think the image of the map on the graphic relating to Global latitude and longitude, where the National Grid border has been removed from the edge of the map, adds a bit of uncertainty in that respect. Having read the piece in more detail, I see that it is stated that the National Grid will not be affected. I’m glad that this is the case as, from a personal perspective, this is a more useful feature than the additional markings showing latitude and longitude.

  6. I don’t think the O.S. need to change the paper maps. What needs to change are SatNav devices to also offer the ability to input National Grid references. This is simple to achieve by adding the correct algorithm to the devices. GPS devices allow for working in either Lat/Lon or National Grid and SatNavs should have the same functionality. My first GPS device (Garmin) did have this functionality however my subsequent device (also Garmin) did not. I think this is to allow the likes of Garmin to sell two devices instead of one.

  7. Stuart Doig

    The Article really isn’t clear about the affects of what your proposing on day to day use of OS maps.

    Re-writing or adding to it to explain that there will be no difference to the current grid refs we see and use would be useful – I’ll hazard a guess that virtually no users of Land-ranger / explorer type maps give their location in lat/long…….

    Other than that, I don’t see a huge impact on our day to day use. Will complete the survey also.

    Most places I’ve been in Europe in the past few years have shifted to GPS compatible maps (misleading description really!) and I don’t think there have been many big issues (for casual users anyway!).



  8. Mark Ward

    Yes, an explanation that this would be additional information rather than alternative information would make the article clearer.
    I find that setting my GPS to UK Grid solves the problem.

  9. I’ve been using O.S. paper maps for 50 years and no-one I know has EVER used lat/long co-ordinates.
    It’s an easy thing to ensure that your GPS (a device I use only when I need to check where I am in the cloud or mist – and at most two or three times a year) is set to UK grid.

    Thus will be an expensive waste of time.

    You have better things to do with the money, like revising hill paths and footbridges in Scotland. Your maps are woefully out of date in places. Spend your money sensibly, not on this stunt.

    1. Hi Alan. We have had the Lat/Long on the map for a long time, but we are looking for comments as we decide which version to use when printing them. We have had some interesting feedback so far as our maps are used in to many different ways, both for personal and business use.

  10. Pingback : Changes afoot on Ordnance Survey paper maps and a useful reminder of the importance of Datums! | Earth Observation and Spatial Analysis

  11. Interesting!
    It makes sense to try this with augmented reality, That way pointing a device (you guys need to make a app for this btw) will cause the overlaid grid atop both a paper map or a GPS generated map.
    Go 3D

  12. Nick

    This is a good blog piece. I don’t understand all the comment around the confusion over the imact of BNG – it’s perfectly clear that there is no impact.

  13. Is showing both datums an option? Eg, black edge ticks for the Airy 1830 and (eg) red edge ticks for the WSG84? I’ve used maps with 1km grid plus two lat/long ticks without problem. Admittedly because I ignored the lat/long anyway and just use the grid by default.

    The ticks are not likely to move more than a few millimetres on a 50k map, so is it an issue? The issue would more be on 10k, 2.5k, 1.25k where it comes to several centimetres which could be several major buildings. But that’s only an issue if you put lat/long on 2.5k/1.25k plans – I’ll have to dig one out of my cabinet to check.

  14. Nick Hopton

    Added after the closing date for the survey, we’ve been away.

    I’m racking my brain to find any good reason for adding a WGS84 geographic graticule to OS 1:25000 and 1:50000 paper or digital mapping. How could such a graticule be of use? Trying to measure from it would be a nightmare and all it would do is introduce unnecessary complexity.

    When it comes to recreational GPS receivers the real problem is that they don’t convert WGS84 geographic coordinates to OS grid coordinates very well, but this is a problem for the GPSr manufacturers, not for the Survey.


  15. Peter

    Chris and Kaled,
    You make interesting comments about the 5mm/year of (relative) UK continental drift in WGS84, though the figure I have in my head for the UK is about 25mm/yr in a SW-to-NE direction.
    But unless you’re going to keep your 1:1,250 paper maps for a very long time, it’s hard to see it making much difference. Still, I like the idea of OS putting a ‘warning’ on the map (especially if they give a definitive measurement).

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