Showing posts with label benchmarks. Show all posts
Showing posts with label benchmarks. Show all posts

Friday, 27 May 2011

Craiginches Littoral

If you've used the new-ish dual path for walkers and cyclists along Aberdeen's Riverside Drive, on the north side of the Dee, between the Duthie Park and the Wellington Suspension bridge, you'll have looked across the river towards Craiginches prison, and seen a network of paths crisscrossing the steep bank (almost a cliff) below the prison and down to the riverside. I've always been aware of these paths, but, somehow, never found the time to go and explore them, to feel what it's like to be there.

So, a few weeks ago, we walked to the Wellington Bridge. This Scheduled Ancient Monument was recently restored and re-opened for pedestrians and cyclists as part of Sustrans routes 195 and 01. Crossing the bridge, we gave ourselves a new perspective by having a good mooch around the littoral on the south bank of the Dee.

The Dee is tidal up to and just past the medieval Bridge of Dee, a couple of kilometres west of here, but the river shore isn't like a sea shore. Although rinsed by the tide twice daily, it's not beaten by waves or swell, and so it has a kind of dusty crust, a dirty patina. And it attracts long-lived detritus. On the day we visited, it was very bluesky bright, with the golden sun low in the west towards the end of the day, and so an atmospheric quality of clarity was lent to our outing as winter turned to spring and as we scrambled along the shore below Wellington Road, under the Ferryhill railway viaduct and crossing the toxic Tullos burn to emerge into the nascent "Granite City Forest" planting at Inverdee (where we saw the husks of the fruit of the sherry-tree).

And finally then on to and under the George VI Bridge, with its impressive civically-emblazoned cutwaters. And there finally (mirroring the supernatural Christian blessing which the stones impart upon travelers crossing the Wellington Bridge) when we climbed onto the George VI bridge we received the more rational secular blessing of orientation, courtesy of an OS Bench Mark on the south west parapet. And we realised that both marks on the stone are essentially the same: only separated in time and the changing perceptions which that passage of time heralds both seek to make sense of the land and its forms, both seek to best orientate people in the world, both seek to give people a sense of security and both try to permanentise their world-view in stone.

And both systems try to tell people where they are and where they're going. The newer with the rational certainty of theodolite and trigonometry, the elder with blind trust in arbitrary dogma and supernatural faith in a supreme being. A newer-yet orientation system, the GPS, is the spun-off civilian hinterland of a militarised economy, and is controlled by unseen and far-off hands and minds. To what priority these far off hands and minds answer we cannot know, because it's secret.

We don't much like the idea of these unseen forces telling us where we're going, so we'll stick with the OS for now. That's our dogma.

A Christian benediction to travelers crossing the Wellington Bridge.
Click for a bigger version, see the word 'HOLY'
(with thanks to reader Bill Watt for this one)





















A secular blessing from the
Ordnance Survey.
Now we really know where we are!

Tuesday, 8 March 2011

March Stones 40 to 43 ABD

Over the weeks and months we've been tramping the ancient boundaries of Aberdeen, and tracing the marker stones or "March Stones" which identify the extent of those boundaries. The word "march" deriving from the Old Scots word translating as "border", we probably see the same linguistic derivation in the "Welsh Marches", meaning "borderlands".

There's all sorts of histobunk available online, and we recommend having a look at both this article in the Leopard Magazine, and this heritage trail leaflet (pdf) from Aberdeen City Council. Both are excellent sources of information and both were compiled and written by our local council's Chris Croly. We thank and congratulate Chris for his work, without which we probably wouldn't have been able to do what we've done in tracing the location of each stone.

Newhills Church, Newhills 
The stones we're going to write about today take us from Newhills, on the eastern face of Brimmond Hill into Bucksburn on the north-west edge of the built-up part of our town, and this marks a bittersweet end to the more rural side of the adventure of visiting all the stones. Bittersweet, for we've very much enjoyed the rural journeys and destinations; they've taken us to places we wouldn't otherwise have gone, and so we've seen and done things we wouldn't otherwise have done. We've also gained an insight into the three four-dimensional (including time) shape of our town that would have been impossible to get by any other means. Actually getting to all these spots under our own steam and being there - in the open air is its own reward. Having said all that, though, we'll not miss the clambering over barbed wire fences. We're getting too old for that sort of thing. (Not really.)


Stone 40 is in a field, south of Newhills Home, and north of the church at Newhills, accessible via the unsurfaced road which runs between the road to Bucksburn and the road from Forrit Brae.




Stones 41 and 42 are on opposite sides of the road into Bucksburn, about 200 yards apart. Stone 41 is on the south side of the road, Stone 42 is on the north.

Gorse!
Barbed Wire!





















We noticed something about both stones that we'd not seen before... You'll notice that stone 41 has what appears to be a little metal button set in its top surface.


Stone 42 has marks which look like a bird's footprint incised on the top surface. Both the button (know as a "Rivet") and the incisions (know as a "Cut Bench Mark) are Ordnance Survey Bench Marks or ("Vertical Control" marks). These mark points of known height, from which other points of know height can be derived through a surveying process known as "levelling". Which is all very boring and technical.

Anyway, there used to be about half a million bench marks but since the advent of the Global Positioning System they aren't needed any more and about half have disappeared in the normal course of land and building re-development.

There is much we hear of today about the need for 'resilience'. We usually hear the term just after some bad weather or natural disaster or something unforseen has caused some sort of infrastructure breakdown. It strikes us as sad that a highly resilient method of mapping the land has been rendered obsolete by a method (albeit much more convenient) which lacks reliability and resilience, and is in the control of foreign powers (albeit 'allies'). We have sacrificed resilient autonomy for tenuous agency.

According to the Ordnance Survey's (OS) website:
Traditional horizontal control stations, triangulation or 'trig' stations (pillars and other survey marks) and vertical control (bench marks) have been the mainstay of control information in Great Britain for many years. They provided the means to link surveys to the national horizontal and vertical datums as well as providing structure to a survey. To do this it was necessary to physically occupy either the triangulation station or bench mark with survey equipment and purchase the control coordinates from Ordnance Survey.
Ordnance Survey has made a commitment to continue to offer traditional control information to surveyors who do not use methods such as the Global Positioning System (GPS) to provide control. However, due to the quantity of traditional stations and the expense of their survey, tied in with the greater accuracy and uniformity that new satellite-based survey techniques provide, it is neither sensible nor realistic for Ordnance Survey to maintain the triangulation and bench mark network.
Thoughts of agency versus autonomy aside, We find all this, unsurprisingly, quite fascinating - these March Stones are (were?) dual use! Not only do they mark the ancient boundaries of our town (political), they are also known reference points which technically and accurately denote the precise shape of the landscape (geographical).

Another fascinating aspect to us is the obsolescence of these items, both the March Stones and the Bench Marks which they host. There is no functional reason for the March Stones to have survived, yet this ancient method of denoting land boundaries
survived functionally in our town well into the Victorian Era, by which time the system of land surveys and title deeds lodged with central authorities had rendered all such physical markers redundant. Yet they survived, and were replaced if necessary because of damage, flood, landslide or whatever.

We cannot help but wonder if there's something very Aberdonian about this. Sure, other towns have boundary stones, but as far as we can find out not even Washington DC (a far newer and completely planned city) has managed to retain all boundary markers in situ. It is as if the new-fangled survey technology of theodolite and trigonometry was distrusted by the city fathers and land-owners of Victorian Aberdeen, it is as if deeds lodged with a notary or in a city hall meant nothing - all that mattered was the good earth, marked out by stone pillars that you could go and see. There is probably some merit in this attitude - it's certainly resilient.

As well as hosting the OS Cut Bench Mark, Stone 42 is adjacent to a "saucer stone" which predates the Victorian Era marks. The stone has two saucer marks, full of moss when we arrived.



No-one knows for sure what the 'saucer' holes were for. Some suggest they may have been filled with molten lead, and impressed with the town's coat of arms - other theories have them as survey-holes, used in some process of surveying the land - this use would be similar to the rivets and pivots of OS benchmarking.

Today, this area is characterised by a busy road which takes traffic from the west into Bucksburn. Being high above a residential area, there is a reservoir, and having good line-of-sight to a population centre, there is a mobile phone Earth-station. These things are vital infrastructure today, but we wonder for how long they will stay as they are, and we frame that question in the context of the March Stones.



Stone 43 is in Bucksburn, beside some lock-up garages, out the back of someone's house in Nether Brae.



Edit, Addendum.

OS Cut Mark Bench Marks are really common:

Geo VI Bridge


Holburn Junction


Music Hall