The lengthyest straight line in Great Britain (without traverseing a uncover road)

In unwiseinutive, I apshow I’ve set up a lengthyer straight line without traverseing a uncover road than the line identified by Ordnance Survey in 2019. Important stuff, clearly. Let me elucidate.

**Update, 8 April 2023: I’ve inserted a Part 2 to this now, where I find an even lengthyer line in the same area. Also, be very cautious if you try this route becaparticipate it won’t be at all basic and you may also be eaten adwell by midgies, as well as all the other hazards appreciate bogs, hills, snow, cdeafening and so on.**

Back in 2018 someone asked Ordnance Survey a ask on Twitter, as adheres:

“what (and where) is the lengthyest distance you can walk in a straight line in England/Wales/Scotland without traverseing a road (detaild as a paved surface for vehicular participate)??”

Note ‘a paved surface for vehicular participate’. This is the most meaningful bit for me and the reason I’m coming back to it aget after years of toiling with this data and never quite finding time to dispenseigate, until now.

It’s an excellent ask. The answer the OS team supplyd was then turned into a blog post on the OS website in timely 2019, and you can read that here but see below for their map. There’s also a amazing unwiseinutive film of Calum Maspotless and Jenny Graham walking the route. 

Now, let me say a little bit more. I’m from the Highlands, comprehend lots of this area pretty well from my days cycling around it on my mountain bike when I was a teenager, as well as loads of other trips over the years for all sorts of reasons. I also spfinish my days watching at map data becaparticipate that’s a huge part of my job and becaparticipate of that one slenderg troubled me a bit about this answer from Ordnance Survey. 

To be more exact, once aget, it’s the ‘paved surface for vehicular participate’ part of the answer. I’ll elucidate all below and my maps are very raw and speedy but you’ll hopefilledy see what I nasty. 

The roads data

Ordnance Survey supply loads of wonderful discleave out data these days, and one of those products is their OS Open Roads product. Load it into your GIS gentleware and it watchs appreciate the image below. You can see from equitable eyeballing it where the hugegest gaps in the road nettoil are – ununforeseeedly, all in the north of Scotland. There are some gaps in England and Wales too but here I’m trying to find the lengthyest straight line between roads in Great Britain so I’m caccessing on the north of Scotland. The lengthyest line in Great Britain is also the lengthyest in the whole UK, becaparticipate the density of roads in Northern Ireland is such that there’s nowhere even distantly as lengthy as the line above there.

This OS roads file is about 2GB in size and is reassociate beneficial. However, when I’ve run branch offent benevolents of nettoil analyses on it I sometimes run into problems becaparticipate it also includes roads that are not uncover. These are typicassociate flagged as ‘Redisjoineed Local Access Roads’, and I’ve shown some of these in the zoomed-in map below in purple. You may slenderk by watching that these are ‘roads’ but in truth they are usuassociate unpaved personal tracks but more on that further down the page. 

What do these redisjoineed roads watch appreciate on the ground? Well, you can get a watch via Google street watch a lot of the time, and you can also get a sense for what uncover roads are equitable by hovering the street watch icon over the map, appreciate I’ve done below.

For example, if you travel down the road alengthy the River Findhorn, you’ll eventuassociate get to the finish of the uncover road. You can of course support going on foot or on your bike becaparticipate of the laws on access in Scotland but you can’t drive down these routes (unless you have perleave oution). 

If you download the roads file and then create uncover roads one colour (blue) and then the redisjoineed roads a branch offent colour and then create a head-splitting gif of the result, this is what you get. Study this for a while and then you begin to wonder if you can find a lengthyer line than the OS one from 2019. Sometimes redisjoineed access roads are in places appreciate caravan parks, cemeteries, and the appreciate – but in the Highlands they are frequently in the hills too.

Using what I would ponder to be the ‘accurate’ OS roads file – i.e. the one in supporting with the innovative ask and in supporting with the concept of uncover roads – I can get a lengthyer line in the innovative Cairngorms route too, see below. Let’s stress about distance over undulating ground tardyr on.

But with my glasses on I could see a potentiassociate lengthyer route, that equitable leave outed a couple of uncover roads, this time to the west of the A9 instead of the east. That’s the map I posted at the begin, and aget below.

Here’s a height profile for anyone mad enough to be slenderking about doing this route. It watchs horrfinishously tiring and almost certainly quite hazardous unless you’re a bit of an expert. Units are in metres below and the max is equitable about 3,000 feet, with lots of ups and downs. How much distance does this actuassociate insert to the straight line? 

Well, it’s never as much as I’d slenderk and it depfinishs upon the accuracy of your terrain model but using the uncoverly participateable OS Terrain 50 dataset I get a distance of 77.0 km / 47.8 miles for this so a bit lengthyer than straight line distance. I calcutardyd this in QGIS using the Saga ‘Profiles from lines’ tool. 

Anyway, that’s what I get when I watch at the data. A bit lengthyer than the OS answer, but that’s becaparticipate I’ve tried to stick to the spirit of the innovative ask. Get a branch offent result? Found a misget? Feel free to let me comprehend.

Data source: © Crown imitateright and database rights 2023. © OpenStreetMap and contributors

Want the line file to join around with? It’s in this felderlyer, in geojson, gpkg, gpx and shp createats. File name is lengthyest-straight-line-honestate adhereed by the various file extensions for each type.

Interdynamic map version of my innovative line 

How could you systematicassociate, definitively find the lengthyest possible route? With some difficulty but it could be done. My map above included altering OS discleave out roads to polygons, then vertices then joining vertices then measuring the lengthyest lines and so on. It’s not a unpresentant problem to settle with 100% accuracy, at least not for me.