[Closed] Definitive OS Benchmarks List - is there one?

No idea what benchmarks are, but this site is great for trig pillars

http://www.haroldstreet.org.uk/trigpoints/

Literally google ‘OS benchmark’ and first page is this: https://www.ordnancesurvey.co.uk/benchmarks/

List is at the bottom in a spreadsheet, though does not include the 190 fundamental benchmarks (I think because they want to keep them from getting damaged).

https://parallel.co.uk/os-benchmark-archive/#17/54.496219/-1.466945/22.9

Interactive map of benchmarks
I no longer use them, just set a point from Rtk gnss and away you go.
Would of been useful back in the 90's when it was £17 a go to get a benchmark value off the OS.

Oops didn't see the 2nd link in the post 👀

Is there a single definitive online list?

The simple answer is No, there isn't. Not as such, anyway.
The OS link that @ashat provides above is the nearest thing to it, but....
The nature of benchmarks is that they have a tendency to disappear - buildings get demolished, roads get widened, milestones get hit by cars, walls get replaced, corners of houses get porches and extensions built onto them, sandstone blocks in old churches get replaced by masons, rock walls weather and fade etc. So the list that the OS provide there was their 'best surveyed & observed guess' as at the last time they had a good look, and in some cases that was 40 or 50 years ago. And the first marks were cut in the 1840s, so the oldest ones have had to survive a very long time now.
For every grid square you can list from the OS database, I reckon you're doing well if you can find 60-70% of what is recorded, especially in urban areas, and even more so in town centres.
The
https://www.bench-marks.org.uk/ site is good for recording what is and isn't there, but it's populated by its volunteers as they visit and find or not find as the case may be. It does however record a few that the OS missed last time they went around the country.
I'd not seen
https://parallel.co.uk/os-benchmark-archive/ before, but looking at some of the ones local to me and their descriptions, it's clearly an extract of the OS database, dropped onto an OpenStreetMap background. Quite handy for visualising what's around you though, but as above, don't expect that everything marked will actually be there on the ground.

The simple answer is No, there isn’t. Not as such, anyway.
The OS link that @ashat provides above is the nearest thing to it, but….
The nature of benchmarks is that they have a tendency to disappear – buildings get demolished, roads get widened, milestones get hit by cars, walls get replaced, corners of houses get porches and extensions built onto them, sandstone blocks in old churches get replaced by masons, rock walls weather and fade etc. So the list that the OS provide there was their ‘best surveyed & observed guess’ as at the last time they had a good look, and in some cases that was 40 or 50 years ago. And the first marks were cut in the 1840s, so the oldest ones have had to survive a very long time now.
For every grid square you can list from the OS database, I reckon you’re doing well if you can find 60-70% of what is recorded, especially in urban areas, and even more so in town centres.
The
https://www.bench-marks.org.uk/ site is good for recording what is and isn’t there, but it’s populated by its volunteers as they visit and find or not find as the case may be. It does however record a few that the OS missed last time they went around the country.
I’d not seen
https://parallel.co.uk/os-benchmark-archive/ before, but looking at some of the ones local to me and their descriptions, it’s clearly an extract of the OS database, dropped onto an OpenStreetMap background. Quite handy for visualising what’s around you though, but as above, don’t expect that everything marked will actually be there on the ground.

This is the definitive answer I was hoping for, thanks for taking the trouble to post.

I've been using the OS database, but as you say significant numbers are no longer there and (often) the details are wrong.

Seems to me the OS list refers to the state of play at some arbitrary point in time. I know one benchmark that isn't on that list (It's on 1914 maps so I guess it fell out of use and therefore isn't on the OS list). As you say many that are on the list, but aren't there IRL. So it seems some fell out of use and dropped off the list in spite of still being in existance, while many others are on the list but have been destroyed IRL.

So I guess the strategy is to find benchmarks using old maps in combination with the incomplete lists that do exist. Then (to assist those coming behind me) add anything I find, or details of missing ones, to https://www.bench-marks.org.uk/ and perhaps trigpointing if I'm feeling enthusiastic.

If you're interested in the benchmarks for historical purposes, a list is relevant. For surveying purposes, they go out of date as the land moves. Isostatic rebound, mining subsidence, aquifer depletion, nearby building or tunnels work, etc, all result in benchmarks becoming inaccurate. GPS levels based on a nominal geoid are definitive, if you can agree which geoid to use!

As per Greybeard, I thought that OS no longer maintain their benchmarks so the positions are largely to be treated with caution.

I thought that OS no longer maintain their benchmarks so the positions are largely to be treated with caution

Basically true, so long as you read it as 'the heights are to be treated with caution'. For the most part the 8-fig reference they give is good,and identifies the X/Y coordinates of the mark's location. As my earlier post says though, just because it was there 20/30/40 years ago, that's no guarantee it's there now.

So I guess the strategy is to find benchmarks using old maps in combination with the incomplete lists that do exist

Yup, that's the way I do it. Now have 2550-odd recorded on https://www.bench-marks.org.uk/, so I've looked for quite a few.

As they say, you learn something new every day. Thanks for posting about this OP. Something else to geek out about 😁

If you’re interested in the benchmarks for historical purposes, a list is relevant. For surveying purposes, they go out of date as the land moves. Isostatic rebound, mining subsidence, aquifer depletion, nearby building or tunnels work, etc, all result in benchmarks becoming inaccurate. GPS levels based on a nominal geoid are definitive, if you can agree which geoid to use!

100% this (plus a lot of them being destroyed). However, until dGPS units became a bit more portable and cost effective, I did still use them occasionally for an approx elevation at some sites I was surveying (working on palaeo landscape reconstruction other errors are much larger).

Yup, that’s the way I do it. Now have 2550-odd recorded on https://www.bench-marks.org.uk/, so I’ve looked for quite a few.

No matter how obscure the subject STW never fails to deliver...

Many thanks!

As they say, you learn something new every day. Thanks for posting about this OP. Something else to geek out about

Seems to makes walks/rides/trips to the shop a little bit more interesting. 🙂

I think you're making it too complicated. Go to the OS site here:

https://osmaps.ordnancesurvey.co.uk/

Just use the standard map, no login or payment needed. Zoom in to street level or so. From the menu at the top, choose PLACES, this brings up a sidebar of overlays for the map, scroll down a bit on the sidebar and Benchmarks is one of the options. I own one on my old house which is rented out, and my nearest here is on Jackie's house, three doors up.