Two new classification criteria for the hills and mountains of Britain

Introducing Jut and On-Top-Of-The-World Mountains

Editor's Introduction. Kai Xu, a researcher from Yale University has been in touch via the website to share two new (to me at least) measures we thought might be interesting to readers of our blog.  Kai is studying new methods of measuring mountains and other forms of topographic relief. Here's more on these two topographic metrics that he thought could potentially provide an interesting new classification criteria for hills and mountains of Great Britain.

The first metric is called Jut. Jut is a measure of how sharply or impressively a mountain rises, considering both its height above surroundings and steepness. Jut also detects a mountain’s most impressive viewpoint—also known as its base—providing non-arbitrary definitions of base-to-peak height and base-to-peak steepness.

The mountains that rank the highest in jut are those with significant local rise—imposing peaks such as Liathach, Ben Nevis, and Sgurr Fhuaran—rather than those with necessarily the highest elevation. Likewise, mountains with the greatest jut in the world are those with the biggest faces, such as Nanga Parbat, Dhaulagiri, Machapuchare, Annapurna, etc. You may read more about jut on this website ( Its info page gives a much more detailed explanation of the concept (  There is also information on the base-to-peak height and base-to-peak steepness a particular jut value corresponds to, along with the direction of the most sharply rising face. For instance, for Liathach, the jut of 591 meters corresponds to a rise of 980 meters at an angle of 37.1° from the southeast.

Here is the top 20 hills of UK measured by Jut.  [Editor's note: To me, it shows what we know to be case: 'West is Best'!]

1 Liathach - Spidean a' Choire Leith 591.0
2 Ben Nevis [Beinn Nibheis] 589.4
3 Sgurr na Ciste Duibhe 551.4
4 Sgurr na Carnach 541.2
5 Stob Coire nan Lochan 528.6
6 Ben Starav 518.7
7 Sgurr Creag an Eich 504.2
8 Sgurr na Ciche 501.1
9 Sgurr Fhuaran 497.9
10 Sgurr a' Mhaim 495.9
11 Beinn Sgritheall 491.9
12 Blabheinn [Bla Bheinn] 484.1
13 Stob Dubh 483.8
14 Aonach Eagach - Sgorr nam Fiannaidh 483.3
15 Aonach Eagach - Meall Dearg 470.1
16 Buachaille Etive Mor - Stob na Broige 469.2
17 Liathach - Mullach an Rathain 462.2
18 Sgurr na Moraich 457.8
19 Carrauntoohil 457.0
20 Sgurr nan Saighead 446.9

These jut measurements are the most accurate ones available since uses a lower-resolution elevation model. More information about these individual statistics can be found in this research paper.

The second metric is called an On-Top-Of-The-World (OTOTW) mountain. A mountain is OTOTW if nothing rises above the horizon of an observer standing at its summit, considering that distant terrain dips below the horizon due to Earth's curvature. OTOTW mountains feature particularly expansive and unobstructed summit views, and dominate over their surroundings.

It provides a non-arbitrary definition of "local high point." There are only a handful You can find an interactive map of OTOTW mountain on this website (; clicking the blue info bubble on the top right corner reveals a description of the concept. There are only 53 of these mountains with a prominence of at least 300 meters in the British Isles, making for a good-sized list.

I got in touch with Rob Woodall to see whether he had heard of these definitions, which he had, although he hadn't followed discussions in detail. Rob identified these 53 hilss from UK and Ireland:

Snaefell 621m visible eg from Grasmoor 
Cuilcagh 665p606
carrauntoohil 1039m
Brandon 952p930
Lugnaquillia 925p838
Mweelrea 814p778
Leinster 795p716
Croagaun 688m P688
Over Fauscoum 792p625
Errigal 751p688
Snaght 615p600
Truskmore 647p560
Croaghgorm 674p522
Slieve League 595p469
Slievecallan 391p368
Ben Nevis
Carn Eige
Snowdon 1038
Ben More 1174p986 View includes Nevis & Lawers
Ben More, Mull View includes e.g. Nevis
Sgurr Alasdair 992m
Ben Macdui
Ben Lawers 1214p915
scafell pike
sg mor 1108p913
goat 874m
ben more assynt 998p835
Klibreck 962p818
Clisham 799m
Beinn an Oir, Jura Paps of Jura visible eg from Ben Lomond
Merrick 843p705 view includes eg Ben Lomond
Penyfan 886p668
Broad Law 840p653
Cross 893p651
Sawel 678p580
Cheviot 815p556
Ward, Hoy 481p481
Sneug, Foula 418p418
Urra 454p409
Whernside 736p408
Brown Clee 540p373
Cwmcerwyn 536p344

Rob noted that "if I'm understanding correctly, several of them don't qualify as higher peaks are visible from their summits (seeing Paps of Jura from Ben Lomond is a very early memory of mine - doubtless it works in the other direction).

Kai responded to his query, clarified that, a mountain being OTOTW doesn't necessarily mean that higher mountains aren't visible from its summit. Rather, it means that even these higher summits would be below your horizon due to Earth's curvature. The horizon, in this case, is defined as the flat plane that intersects the summit and is perpendicular to the direction of gravity at the summit. "Above the horizon" refers to the side of this plane opposite the direction of gravity. I've attached a diagram of this concept:

Attributions: Measurements are made possible with Andrew Kirmse's dataset of every mountain in the world, as well as the Copernicus GLO-30 digital elevation model, EGM2008 geoid model, and Google Earth Engine. Jut and OTOTW are concepts developed by Kai Xu.

Pinnacle Points

Jamie Breault has also been in touch to say that inspired by Kai Xu's work, he started a project to find all points on Earth from which no higher point can be seen. He calls these Pinnacle Points - view map. For Pinnacle Points above 100 m of prominence, the 5 present in the British Isles are really well distributed: 1 in England, 1 in Wales, 1 in Scotland, 1 in Ireland, and 1 in the Shetland Islands.

Dave Chaffey

Dave is the webmaster for RHSoc, so if you have any ideas for articles or corrections, do feedback via the Contact Us. I'm relatively new to the Relative Hills, although joined the Marilyn Hall of Fame in 2022. I completed the Munros in '94, am around 200 Corbetts and working on the Marilyns of England and Wales by public transport and bike to add to the challenge!

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