BrownhillsBob's #365daysofbiking

On a bike, riding somewhere. Every day, rain or shine.

Posts tagged ‘ordnance survey’

#365daysofbiking Feeling flush



March 11th – I had time to spare so hopped onto the restored canal at Droitwich for a mooch. Just under the railway bridges in the last entry, I noticed this relic of the Ordnance Survey.

Flush Bracket 480 is one of a range of such brackets intended as mapmaker’s datums, the slots in which were for mounting surveying equipment at a known datum – in this case 28.7490m above sea level (the Newlyn Datum).

Now redundant as cartographer’s aids, these are more a historical curiosity than anything else, but I still get a buzz from spotting them in the wild.

You can find out more about this one here.

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#365daysofbiking Still amazed:

November 9th -One thing I never take for granted is my biking technology. From disc brakes to LED lights to tough tires, things are very much better in the saddle these days than the four decades or so ago I started to ride a bike.

One thing that would have blown my mind even in the 1990s is the current GPS bike computer technology available to me. I ride down darkened lanes, with the soft glow of a device on my bars indicating my position on a scrolling Ordnance Survey map. Overlaid on this are street names, and I get warnings of sharp bends and hazards. 

Of course, I know these lanes like the back of my hand, but when off-piste, it’s a godsend. If anyone had shown the young me this device, it would have blown my tiny mind.

Old hands scorn the modern technology, but not really is a wonderful thing.

May 7th – The third day of a long weekend, May Day bank holiday, and I knew what to do. The forecast was for a beautiful, hot day so I hopped on a very early train to Macclesfield, and rode back via the Moorlands, Roaches, Morridge and Weaver Hills.

You can see a full gallery from this ride on my main blog here.

Just on the moors near Thorncliffe, I found this curiosity, something I’ve never seen before – a UK Meteorological Office remote weather station. I have no idea why it’s here specifically, or for the oblique angle it subtends to the road, but it is fascinating, populated with a host of instruments measuring rainfall, win speed, polled count, air quality and other metrics of the atmosphere. All this seems to be remotely operated by telemetry link.

Also in the compound is a GNRR sensor for the Ordnance Survey, a Leica device to provide calibration for GPS signals.

A fascinating and slightly haunting thing, right in the middle of nowhere.

November 5th – Oh, and this. Up on the Chase at Rifle Range Corner, a wee accuracy error.

Most of the fire gates on the chase have their OS grid reference stencilled upon them. Helpfully, my bike GPS also give me a grid reference. 

Checking with a paper map, they’re wrong, not the computer.

That’s a bit regrettable…

July 22nd – A fast, enjoyable 50 mile ride on an afternoon bunked off work saw me calling at Barton and then Rosliston for excellent carrot cake on a hot, sunny day. On the way, I took in a little of the canal near Barton Marina, and spotted the benchmark in the bridge just by Barton Turn. I think that’s the first I’ve ever seen highlighted with paint and it also seems rather high.

It must be genuine, but I sense a story here. Any ideas?

Apriul 12th – I must have passed this hundreds of times without noticing it. Facing the footpath on the Birmingham Road, just on the edge of the Highwayman Car Park at Shenstone Woodend, this Ordnance Survey monument. Cast Iron, now at a jaunty angle, it sows a benchmark in the absence of a building to carve one into.

I had no idea these ornate cast iron ones existed, and they seem relatively rare. A fine, uniquely British thing.

August 30th – Out for an afternoon spin, I came through Wall, just south of Lichfield. Just as I was approaching the junction of the old Watling Street and Wall Lane, I noticed that on the side of the old barn at Manor Farm, there was an Ordnance Survey Flush Bracket. This is a type of benchmark that was used for map surveying – in the notches on the plate, surveying equipment could be mounted at a height known to the surveyor, called a Datum, or benchmark. The flat tip of the arrow indicates the precise height  point, and this is benchmark reference S8958. 

I must have passed this wall hundreds of times and have never noticed this feature.

August 22nd – near the top of Mere Hill overlooking the Manifold Valley near Calton in the Peak District stands this old, redundant stone gatepost. Initially, its survival long after the field boundary it marked was removed is puzzling, until one notices the Ordnance Survey surveyor’s benchmark carved into it. This is the usual explanation for any such stone posts, and the majority are no longer used, but it does make a fine cattle scratching-post.

October 10th – I’ve been studying the detail of buildings lately. Small things. Architraves, chimneys, corbels, pediments, lintels. Airbricks, panels and frescos. Sills, doorways and sashes. There’s a huge variety of stuff in the everyday. In a quiet Tyseley backstreet, my gaze was caught by this ornate ventilation brick made from pressed terracotta in an otherwise plain factory wall. As I stopped to take a better look, I noticed the Ordnance Survey benchmark carved into the wall. A fixed datum at a measured height, these may not be used so much now, but they’re a real signal of permanence. 
The things you see with your eyes open… 

May 7th – The odd symbol on this markerstone will be familiar to many who study old buildings, but it’s purpose is not widely understood. It’s a surveyor’s benchmark, used by Ordnance Survey mapmakers. The horizontal bar at the top of the mark indicates a known, measured height above mean sea level, which the surveyor will know and can then use to reference other measurements. Benchmarks can exist anywhere, but are easily spotted on churches, bridge abutments and stone gateposts. Sometimes, as in this case by the A51 near Whittington Golf Course, a stone is placed for the purpose. These are a secondary reference to trig points. It is actually an offence to remove or obscure one.

In the days of new technology such as global positioning and satellite imagery, benchmarks are not as commonly used as they once were, but every surveyor that works for the OS is still taught to carve them. They are a tangible, visible footprint of the gorgeous heritage of British map-making that the Ordnance Survey represents.