Destroyed? Yes/No?

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Destroyed? Yes/No?

Postby alansmeaton » Thu Sep 22, 2016 8:54 pm

Hi all,
When I search around my local area some of the TP's, sometimes buried blocks, are marked as destroyed. Some of these have had no visits or are in the middle of nowhere in a place that disturbance is unlikely. Why has the destroyed classification been applied? Is there a particular source/reason?
Thanks
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Re: Destroyed? Yes/No?

Postby agentmancuso » Thu Sep 22, 2016 10:28 pm

Where trigs without visit logs are marked as Destroyed it's almost certainly because the Ordnance Survey themselves recorded the station destroyed in the OSGB36 archive; generally the appropriate extract from this is visible on each trig page. There's a white box towards the top right; if you scroll along you'll see the 'destroyed' flag.
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Re: Destroyed? Yes/No?

Postby Cootking » Wed Jan 03, 2018 12:53 pm

Did the OS actually send someone with tools out to the middle of nowhere to break up an underground structure? Seems a bit of overkill. Why not just leave it and have another cuppa? How sure are we that they've been physically destroyed or are many awaiting the GPS and trowel?
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Re: Destroyed? Yes/No?

Postby agentmancuso » Wed Jan 03, 2018 1:23 pm

I don't think the OS themselves ever destroyed stations, except perhaps on a tiny handful of occasions following disputes with landowners. I imagine that in most cases the OS updated their records following notification from reliable authorities such as the Highways Agency or significant private contractors that stations had been disturbed during road building or other landscaping works.

How do we know the stations have in fact been destroyed? Inductive reasoning; the number of stations marked as destroyed by the OS but subsequently discovered to be intact is very small, whereas the number of stations marked as present by the OS but known to be destroyed is large. Hardly surprising, given that the OSGB archive hasn't been updated 1989 or thereabouts.

On the other hand, the level of disturbance which would lead surveyors to consider a station destroyed might in practice be invisible to the naked eye; for our purposes, it might look to be in perfect condition. So don't let an OS destroyed flag hold you back if you're getting twitchy with the trowel. ;)
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Re: Destroyed? Yes/No?

Postby ted » Wed Jan 03, 2018 7:58 pm

I've never properly understood how the OS did relocate buried stations. The usual bagger's technology seems
rather primitive - I can't quite envisage a surveyor crawling around on the ground with a long-bladed screwdriver
and I would suppose that, originally, GPS wasn't an option for OSGB36. The OS station sketches often seem to be
more of an aide-memoire than a formal description of the site; maybe other detail was passed on verbally?
Use of a metal-detector seems the most likely alternative although, so far, noone on TPUK seems to have had
more than the odd success with these.

> I imagine that in most cases the OS updated their records following notification from reliable authorities

Another possible interpretation is that the OS marked block as 'destroyed' to indicate 'couldn't find the bloody thing' :)


Best wishes for 2018


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Last edited by ted on Wed Jan 10, 2018 2:15 pm, edited 1 time in total.
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Re: Destroyed? Yes/No?

Postby agentmancuso » Fri Jan 05, 2018 12:21 pm

>Another possible interpretation is that the OS marked block as 'destroyed' to indicate 'couldn't find the boody thing

Much like us then ;)

I have a vague idea that somewhere in the lower vaults at Mayfield there existed full construction details for all stations, not just the sketches that were made public for those few that became Passive Stations.
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Re: Destroyed? Yes/No?

Postby TrigJS » Sat Sep 22, 2018 8:57 pm

A few months ago I found a block that the OS had logged as destroyed.

http://trigpointing.uk/trig/21496

The block was at the expected location, was in a good condition and didn't look like it had been disturbed.

Based on the boreholes (water or gas monitoring?) near to the block (block was at the edge of the field up against a hedge) I think the area might have been used for quarrying and/or landfill. Given all the earth works this would have involved the OS probably just assumed the block had been destroyed or disturbed hence the destroyed log without actually having sought out the block to confirm its status.

More broadly I have also wondered why some TPs (blocks especially) are logged as destroyed when in some cases it seems unlikely that this would have occurred. I agree that an OS log of destroyed in some circumstances might just mean the OS surveyor at the time couldn't easily find it!
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