OpenStreetMap
The helpful householder at 88 Main Street, Carlton pointed out the Benchmark on his house:—
Benchmarks were originated by Ordnance Survey in the days of mechanical measurement:—
Ordnance Survey Bench marks (BMs) are survey marks made by Ordnance Survey to record height above Ordnance Datum. If the exact height of one BM is known then the exact height of the next can be found by measuring the difference in heights, through a process of spirit levelling.
That neatly explains the BM numbers which you can find on old maps. In this modern Star Trek age, when anyone armed with a communicator (sorry, I mean mobile phone + suitable app) can measure their position & height above mean sea-level, the Ordnance Datum Newlyn is a touch out of date.
Unfortunately, I do not seem to be able to find a simple method to attach a Benchmark reference to a house in JOSM that will show on the map.
You will not be able to find a Main Street in modern Carlton NG4, as that is the name that the street had in 1876 when number 88 was Carlton’s first Police Station (the road is called “Carlton Hill” today). The sole modern reference to it remains in the placard for the nearby Methodist Church, which is on the same street:—
Many thanks to Mr Bernard Leaper for his generosity in sharing the results of years of research with me. He tells me that the last Inspector was Inspector Marshall before the old Station was moved to it’s current location (though not the same building) on Cavendish Road (when I surveyed it, the lady inside the Police Station told me that it was due to move again). The final use as a public building for 88 Main Street was in the 1950s as a Civil Defense Headquarters. Mr Leaper also finally answered my month-long search for the original centre of Carlton, which was Carlton Square.
Today, Carlton Square is both a retail area and also a street, but originally was Carlton town’s centre, where the modern Cavendish Road, Burton Road, Station Road and Carlton Hill join. Like most towns, the square was originally faced with busy shops. Today, it is partly composed of brutalist concrete 1950s buildings, the side of a Tesco car-park & traffic, and most folks have completely forgotten it’s original place as the heart of Carlton.
Coda:
Wednesday 13 update:
I’ve moved the Carlton suburb node from it’s position at the top of the hill to the old town centre (the actual place, as detailed above). Is there an actual ‘official’ Carlton town area/boundary? (and where is it?). If so, then the node can be deleted & replaced with an area, which would be much more satisfactory.
I’ve noticed in the past that the Normans tended to place themselves on the top of hills, whereas Angles/Saxons tended to live in the valleys or, at the most, on the side of hills. In any case, that is where Carlton has always been (at that crossroads), so that is where the OSM map should show it.
Discussion
Comment from Warin61 on 13 July 2016 at 07:16
I have used man_made=survey_mark for similar things .. See http://www.lpi.nsw.gov.au/__data/assets/pdf_file/0020/208280/Protecting_survey_marks.pdf for some different kinds of survey marks.
See https://help.openstreetmap.org/questions/44030/how-should-we-tag-ordnance-survey-bench-marks for more comments..
Some of these have become tourist attractions! These have been mounted on concrete plinths … however some have been stolen, vandalized … the more popular ones have had ‘tourist marks’ placed a little way off the actual survey mark and the true survey mark hidden in some way.
Comment from andy mackey on 13 July 2016 at 08:21
For a few months in the summer of 1965 i laboured for the OS, I chiseled three of four BMs, one i remember was in blue railway brick which was/is as hard as concrete. I think you mentioned Staffordshire Bricks before. The Level Scope had three cross hairs and the 8 foot ?? staff was read to .01 foot about 3mm. The difference between top and bottom crosshairs was 1/100th the distance from it, this allowed the forward and back readings to be kept as similar as possible to cancel errors in the spirit level. I was supposed pace up to the instrument then pace onward the same amount, I often miscounted and was called in or out, but for many many years after leaving the OS I would still occasionally find myself counting paces! Keep up the good work.
Comment from alexkemp on 13 July 2016 at 12:16
Thanks https://www.openstreetmap.org/user/Warin61 & https://www.openstreetmap.org/user/andy mackey, useful as always. Since the Wiki advice is NOT to use type=benchmark NOR survey_point:type=benchmark (essentially, avoid type outside relations) I used:
Unfortunately, and as you can see from the photo, there is zero reference or altitude information, which reduces it’s utility a lot. Still, you always remember your first, do you not?
Re: Staffordshire Bricks (aka Tamworth Blue Brick):
see the brick porn within Nottingham Suburban Railway, Part 3
Comment from alexkemp on 13 July 2016 at 12:38
Just in case it may be significant or helpful, here is the GPS info extracted from the JPEG of that Benchmark (IIRC ImageMagick is required to get the identify utility under Linux):