What do the numbers mean on a Trig point up a mountain?

Question

Any websites that will show a pic indicating what each number means??

Answer 1

Here's a brief, clear explanation:
http://en.wikipedia.org/wiki/Trig_point

Here's an interesting UK site:
http://www.jeremyp.net/trigpoint/index.php

Answer 2

Ah! The good old days when surveyors were surveyors using Theodolites instead of Satellites.
All over the UK and at a height capable of being seen from the next trig point, a flat topped concrete platform is fixed in the ground.
The numbers you refer to is the height above sea level at that point. Somewhere on the horizon and in sight of it is another trig point. By this time you will have noticed that trig is short for trigonometry.
Using the Theodolite and the angle it makes you can work out the difference in height between the two and the distance if required.
When building, the datum the height above sea level, is referred back to these trig points eventually.
These points are essential in planning drainage and sewerage systems. The Theodolite has a second cousin called a Dumpy Level but it can't measure angles.

Answer 3

The brass plate attached near the base of a trig point consists of an arrow with a line above it, this line is the Bench Mark (BM) - the point at which the height is measured. In the UK all heights are measured relative to what's known as the Newlyn Datum, this is a point in Newlyn Harbour in Cornwall which represents 0 metres.

The metal plate will contain the letters OS which stands for Ordnance Survey - the UK's national mapping agency. There will also be the letters BM for Bench Mark and at the bottom of the plate a number such as S1234 this is the Flush Bracket or Levelling Plate Number (FBN or LPN) and all this is is the reference number of the trig point, nothing more interesting than that I'm afraid.

The FBN is important as it identifies the precise trig point in question and enables the land to be surveyed using a method of surveying known as geodetics and a system called triangulation (which is what trig is short for).

More about trig points and trig point database from the OS...
http://benchmarks.ordnancesurvey.co.uk/pls/htmldb/f?p=111:13:12782873437371231328::NO:13::

About trigpointing...
http://www.trigpointinguk.com/