What is this symbol?

Post by **dsco** » Tue 20 Feb, 2007 6:10 pm

Does anybody know what this peculiar mark is? It’s carved into the stone wall on Dock Street, just above street level.The buildings around there have all sorts of unusual features – old loading bays up on the first floor for example, with what look like struts or supports for pulleys and lifting equipment. This thing looks almost Masonic though!

Fraggle rock lover · Post by **Fraggle rock lover** » Tue 20 Feb, 2007 9:56 pm

It looks like an arrow pointing to the level that the water probobaly once reached

rikj · Post by **rikj** » Tue 20 Feb, 2007 11:17 pm

It's an Ordnance Survey benchmark that indicates a known vertical elevation. Surveyors would place a levelling rod (bench) into the horizontal groove, which is highlighted by the three arrows underneath. Wikipedia explains the whole thing a lot better than I can.Once you start to look for them they start to appear all over the place.

munki · Post by **munki** » Wed 21 Feb, 2007 12:56 pm

I found this one on Great George Street this morning, outside Carpe Diem.

Phill_d · Post by **Phill_d** » Wed 21 Feb, 2007 3:00 pm

Here's a nice concrete example out in the sticks with the serial number on

Phill_d · Post by **Phill_d** » Wed 21 Feb, 2007 4:36 pm

Ordance survey bench mark s3862

rikj · Post by **rikj** » Wed 21 Feb, 2007 11:55 pm

That looks familiar phil!There must be a website somewhere where these are all listed.

munki · Post by **munki** » Thu 22 Feb, 2007 8:02 am

If there isn't, then let's make this that website.

Phill_d · Post by **Phill_d** » Thu 22 Feb, 2007 10:34 am

Sounds good to me Rik mate!!

bigpants · Post by **bigpants** » Thu 22 Feb, 2007 2:19 pm

if you look on OS sheets you will often see benchmarks detailed with their level above ordanance datum (AOD). funnily enough although the OS sheets are pretty accurate plan wise, many of the benchmark levels shown are hopelessly out due to not being re-surveyed with modern methods and movement of the structure its on. The ordnanace datum used is mean sea level at the harbour at Newlyn, Cornwall.the one pictured on the concrete pillar - this could be triangulation point - does it have bronze plate on the top for setting up a theodolite/total station? they are used as fixed reference points. there's one in the field behind the water tower at Garforth. Hi everyone by the way, im new (as i guess are most people!)