Kelso FBM Aux1

[agentmancuso]

Does anyone here by any chance have access to a location sketch for Kelso FBM Aux 1 / H2NT7431 ?

Regards,

Bernie

[Sagina nivalis]

I had this down as H2NT7531 - as does TUK
This implies http://gps.ordnancesurvey.co.uk/stat...f/H2NT7531.gif The link works - hopefully it's the right location ?

H2NT7431 seems to lead nowhere - neither gif nor jpg

HTH: Good luck

[agentmancuso]

Thanks Rob, Ted has just sent me the same link.

I've never used the "http://gps.ordnancesurvey.co.uk/stationpics/...." stem before, having always relied on just searching the OS passive station database or the TrigTools site. There seems to be some confusion with the numbering for this berntsen too - both H2NT7531 and H1NT7431 appear.

I'll get it next time and down that way.

Cheers,

Bernie

[j.i.wilson]

It looks to me that the original station (H1) has been destroyed and replaced by H2. Tht would explain the two sketches.

There will be no point in searching for H1.

Being a Bernsten marker it will be more difficult to locate than a "proper" FBM which is a significant monument.

I may be telling my granny how to suck eggs - but - the reason there is an Aux is that the original FBM is badly sited for GPS observations. This is neary always due to tree cover at the original site.

BTW - I managed the Project that took observations at the FBMs. During the Project I visited H1 - and couldn't find it!! Hence H2.

Hope this helps

On second thoughts - H1 would have been the FBM itself and may still be there. No matter - I definitely remember having problems when I looked for this mark. There is certainly some doubt about its whereabouts. Sorry I cannot be more (!) help.

Ian Wilson

[agentmancuso]

Interesting stuff. Certainly H1NT7531 (Kelso FBM) is still extant - I saw it on Thursday, though only after poking around for a good while. And although I couldn't find H2NT7531 (Berntsen), others have recently. The same berntsen is referred to by the OS as H1NT7431!

>BTW - I managed the Project that took observations at the FBMs.

I'd unthinkingly but correctly assumed that the 'aux' was backup for the FBM, though I'd have guessed something more technical than tree cover would have been the main cause. What then is the relation, if any, to the nearby surface block?

[j.i.wilson]

Others my have a better recollection than me. But my best memory is.....

So far as I am aware there was never any "backup" for any of the FBMs. Each FBM consisted of three height marks. The first (and most obvious) is the small pillar - or, more correctly, the bolt in the top of the small pillar. Adjacent to this is a small manhole. In this chamber are two further marks. One is a bolt and the other a flint set in concrete. The precise height relationship between all three marks was measured some time after the mark was built - to allow settling. The flint was considered to be the definitive mark. Opening a chamber was a "big deal". Permission was required from Chief Surveyor of Geodetic Surveys no less! When opened they were often flooded!

Each FBM was (is) on a geodetic level line (naturally). Along these lines are what was termed "brass". This may be a bolt (or rivet) or, more commonly, a flush bracket (as found on trig pillars). In the event that a FBM was destroyed the team would measure from "brass" through another "brass" to the new FBM and then on to the next "brass" and onto a fourth "brass" point. The derived heights would eb compared to the previous and so the height of the new FBM derived. This whole procedure would eb repeated at least twice.

So far as I remember it was rare to replace a FBM. Because they were built in "safe" places it was (still is) rare for a FBM to be destroyed. I only came across one relacement FBM in my (42 year) career - somewhere near Grimsby I think.

[j.i.wilson]

>BTW - I managed the Project that took observations at the FBMs.

I'd unthinkingly but correctly assumed that the 'aux' was backup for the FBM, though I'd have guessed something more technical than tree cover would have been the main cause. What then is the relation, if any, to the nearby surface block?

Agentmancuso - are you ex OS or one of the contractors (Loy?) who were allocated some of the FBM GPS work? Either way I my know you.

Tree cover was a real nuisance at FBMs. Because they were built well before GPS they were not well positioned for sky view, and, even where they were, tree growth subsequently often crippled them for GPS. Because of the precise GPS being observed the OS requirement for sky view was onerous - uninterrupted down to 10 degress of the horizon I think.

As to the surface block. C1 indicates it is a National GPS Network passive station. It is not connected with the FBM in any way - except via GPS obs. It is highly unlikley that it was ever "levelled" to. The "C" indicates it was not a pillar or other legacy mark. I am trying to retrieve the docment that fully describes the new naming convention - which, as it happens, I designed!

Regards to all

[ted]

Ian,

Welcome and t:hanks for the very useful information from an OS 'insider'

> Because they were built in "safe" places it was (still is) rare for a FBM to be destroyed. I > only came across one relacement FBM in my (42 year) career - somewhere near
> Grimsby I think.

Nearest FBM to Grimsby would be Immingham but I guess that you are thinking of Hibaldstow. The other replacement that I can think of is Kirkby Stephen. I assume that the originals were the victim of road-widening in both cases.

> I am trying to retrieve the docment that fully describes the new naming convention -
> which, as it happens, I designed!

This one?
www.ordnancesurvey.co.uk/oswebsite/gps/osnetfreeservices/about/faqs_osnet.html#9

And whilst on the subject of FBMs, would you happen to know anything about
Patrington? In a private garden, house rebuilt about 6 years ago, FBM might have been destroyed then. I emailed Richard Short last year and he thought it might still exist but I don't think anyone has been able to obtain permission to visit and confirm one way or the other.


Regards
Ted

[agentmancuso]

Agentmancuso - are you ex OS..?

Indirectly, but a different wing. I managed the OS (retail) agency in Glasgow for a few years, covering the deregulation and introduction of the Options branding.

As to the surface block. C1 indicates it is a National GPS Network passive station. It is not connected with the FBM in any way - except via GPS obs.

I'd wondered because the two often seem to exist in close proximity.

Cheers,

Bernie

[agentmancuso]

The other replacement that I can think of is Kirkby Stephen. I assume that the originals were the victim of road-widening in both cases.

Also Glen Moriston for the same reason, and Lairig for a similar if more dramatic reason.


Regards,

Bernie

[agentmancuso]

So far as I remember it was rare to replace a FBM.

Another FBM query, while I've got the expert on the line so to speak - why are some e.g. Kelso and Hawick - at groundish level, rather than the usual cube like Newcastleton?

[j.i.wilson]

OK - honest answer - don't know

However I would hazard an educated guess....

I would suggest the marks at ground level are actually a buried pillar. Some marks have been in so long that ground level has risen

Alternatively

It is possible bed rock was at the sureface and a pillar was deemed unnecessary. They did, after all, seek locations with exactly that property.

There is also the possible effect of changing specification.

As an aside

Many questions of this type (see "total confusion") are born from an assumption that a rigid set of rules and procedures were followed. Now this is true regarding some aspects - but it must be remembered that each location has its own set of circumstances which may require some imagination to overcome. In addition different teams covered different parts of the country and nationwide meetings rarely if ever happened.

This combination of circumstances allowed different solutions to develop.

Now, in this age of instant global (never mind national) communications these differences are coming to lght.

[RodS]

I'd had it bookmarked for ages, but then had completely forgotten about it. Oddly enough, just after posting it here I found my way to it again, through the benchmark database somehow. It might belong to Rod S. if I remember rightly.

Based on my notes, but Ian Richardson's handiwork on the web page. Most pictures from Iain M and others on T:UK

[RodS]

There seems to be some confusion with the numbering for this berntsen too - both H2NT7531 and H1NT7431 appear.

I'll get it next time and down that way.

I'm sure that I answered this one somewhere else a few days ago!

H1NT7531 is Kelso FBM

Kelso FBM Aux 1 was originally known as H2NT7531, but was later renumbered to H1NT7431 to reflect its actual location. Howver, its location sketch got left behind at H2NT7531.

[agentmancuso]

I'm sure that I answered this one somewhere else a few days ago!

Same person, different place! Thanks again

Bernie