Creag na Caillich was recently dropped from the list of Munro Tops after a small team of independent surveyors proved it to be under 3,000ft high. So who are G & J surveys, and why does their work matter to peak baggers?

If you’re working your way through the Munros, the Corbetts or any of the other seemingly endless mountain tick lists, then you’ll want to keep a close eye on the efforts of G & J Surveys. This small team of three friends - John Barnard, Graham Jackson and Myrddyn Phillips - have dedicated the last few years to exploring the hills with a very particular aim in mind. Using survey-grade GPS equipment, they measure the height of hills with incredible accuracy, often playing havoc with the official checklists as they go. Remember when the Fisherfield Six became the Fisherfield Five? That was G & J surveys. More recently they proved that Creag na Caillich can’t in fact claim Munro Top status. So what motivates these three hill enthusiasts to go around measuring mountains? We caught up with Graham Jackson to find out.         

Why is it that so many of the mountain heights recorded on Ordnance Survey maps are incorrect?

It isn’t that they aren’t correct; it’s just that there is some uncertainty in the measurement. The OS is charged with mapping the whole country at least once every five years, and that’s a huge task. They do it by flying a plane over the terrain they are mapping and photographing as they go. Then they turn the plane round and retake the images. When they feed two images taken from a different angle into a machine, that gives a 3D picture and from that you can measure height. That technique is accurate to plus or minus three metres, so if you’re a map user then it’s perfectly fit for purpose. It doesn’t matter if a mountain is shown on a map as 3,000ft high or 3,010ft high - you can still get to the top of it.

So why is accuracy suddenly more important?  

It’s really down to hill lists. The majority of lists have some kind of criteria - so Munros, for example, are all 3,000ft or more. If you have a 915m height on a map then that hill will be classed as a Munro - but it might in fact be 918m or 912m. People with an interest in peak bagging want these lists to be accurate.

I hear you’re a peak bagger yourself - did that help spur your interest in measuring mountains?

Yes, the walking group I’ve been a member of since 1989 has been ticking off Munros since the early 1980s and that definitely got me thinking about it. Sometimes you’ll start to climb a list of hills and you get halfway through when the authors come out with revisions that they’ve taken from the maps. You end up thinking ‘there must be a better way than this’.

How did G & J Surveys get started?

Again, it was through our walking group. When you’re in a pub you start talking about things and inevitably the conversation will arrive at how it’s possible to know the highest point of a hill because they have so many humps and bumps on them. After one of these conversations back in 2006, John [Barnard] went away to research this some more and discovered we could work this out using an Abney level - basically a small spirit level. We got a little more into it and bought a surveyors’ level and staff, and then finally in 2008 John said that we could do with a survey-grade GPS and that’s when it all really got started.

Tell me a bit more about the technology you use to measure mountains - how accurate is it?

We use survey-grade GPS equipment that links into a network of OS base stations. The system is called differential GPS and you can get down to amazing levels of accuracy - literally a couple of centimeters. By the time you get to that point, you’re worrying about where the vegetation stops and the mountain begins. 

What do you count as your most important discoveries?

We reclassified two Munros - both of which unfortunately went down rather than up, so there are now 282 Munros rather than the original 284! The first was Sgurr nan Ceannaichean and the second was a hill called Beinn a’Chlaidheimh in the Fisherfield Forest. That last one meant that the famous Fisherfield Six became the Fisherfield Five.

The hill that made the greatest impact was probably Mynydd Graig Goch in Snowdonia, which had been listed as under 2,000ft and was actually just above - making it a new Welsh ‘mountain’. It was the time of the banking crisis, there was doom and gloom everywhere, and while everything in the world was going down here at least was something that was a bit of quirky good news. 

Another significant one was back in 2010, when we discovered that Glyder Fawr was over 1,000m and therefore had to be added to the Welsh 1,000m challenge hill race.

What do peak baggers think of your work - do you get any grumpy compleaters who don’t like the fact that you’ve demoted one of their mountains?

A lot of people are really supportive of what we do - one chap called Alan Dawson has bought his own kit so that he can help out, and some guys in Ireland who we visited recently are starting to measure the hills over there. Others don’t believe that what we’re doing is as accurate as claimed, and of course some people take it badly when a hill that they have climbed is demoted - but that’s why it’s so important for those lists to be accurate, because a lot of people use them.

How ‘official’ is the work that you do?

We have a good working relationship with the Ordnance Survey and the SMC will take any changes we find provided that the OS verifies them. What happens when we measure a hill is that we submit our files to the OS, which processes them using their software and confirms the results for us. 

When you set off to survey a mountain that you think could be a candidate for promotion or demotion, is there a frisson of excitement there?

It is exciting! Both John and I studied chemistry at university and come from a background involving measurement, and having that background you’re always motivated to see if there’s something that can be done better and whether measurements will help. 

How much importance do you place on tick lists yourself?

I’ve done the Munros, the Corbetts and the Grahams, and I think that working your way through a tick list focuses the mind - if you don’t have a focus in view then you don’t tend to do as much. But are hill lists important to enjoying the uplands of Britain? Not really. The things that stick in my mind from being in the hills are individual moments…like walking in the Mamores and seeing a golden eagle gliding right by me, or being in the middle of Rannoch Moor on a remote Graham when a flock of snow buntings flew by. Things like that enrich the experience more than just meeting an objective. 

But you’d still consider your efforts to make the lists more accurate important?

Personally, I think that if you’re going to have a list based on any criterion then it should be as accurate as it can be or it’s a pointless exercise. There is a lot of discussion about this sort of thing as well. One of the first hills that John and I first measured was Birks Fell in the Yorkshire Dales and there was so much controversy on forums and on social media about where the summit was. We went up there with a level and staff and found the highest point incredibly easily. Why pontificate about it when you can just go up there and measure it?

What peaks do you have in your sights next?

We usually get together in December and plan for the year ahead. In winter we choose objectives that are nearer and can be completed in a short day, so we might just keep our hand in by nipping into Wales and measuring a hill that’s borderline on the list of HUMPs. Our broader objectives are to finish some of the hills on the Munro/ Corbett and Corbett/ Graham borderlines, working with the SMC. There are some hills in Cumbria we want to do too, such as Illgill Head which is currently listed as 609m but could just make it over 2,000ft. Let’s put it this way - we’re certainly not short of challenges!

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