Welcome to Hydons Ball and Heath, it was one of the earliest acquisitions for the National Trust and is a memorial to one of their co-founders, Octavia Hill, who died in 1912. It’s one of the highest points in Surrey and the steep, wooded, south-facing slope commands magnificent views across the surrounding countryside towards the Sussex border.
The trigpoint sits at the peak of Hydon's Ball which is 190 metres above sea level. The Trigpoint here (TP4093) has the Flush Bracket S5653.
Trigpoints are the common name for "triangulation pillars". These are concrete pillars, about 1.2 metres tall, which were used by the Ordnance Survey map the country. They are generally located on the highest ground in the area, so that there is a direct line of sight from one to the next. By sitting a theodolite (an accurate protractor built into a telescope) on the top of the pillar, accurate angles between pairs of nearby trigpoints could be measured. This process is called "triangulation".
A major project to map out the shape of Great Britain began in 1936. The network of triangulation pillars, with accurately known positions, led to the excellent OS maps which we can enjoy today.
The Cache
In order to find the cache, you need to note down some info from 2 stages first.
At the starting co-ordinates there is a large Green building, and on one of the doors, there is the suppliers label - What are the last two digits of the Order No.? 200AB
At stage 2 and just past the Trig Point, there is a National Trust Information Board which has a picture of the painting by John Singer Sargent - make a note of the missing numbers - 18CD - 19EF
Due to proximity with another cache, the cache can be found a little stroll away at: -
N51 08.(B*2+A) (C-A) (B+D-A) W000 36.(D/2) (F+A) (E*2+A)
You are looking for a Green PET Tube - make sure you sign the log book. Tweezers might be handy if the log book has been pushed in too far!
About Ye Ole Survey Monuments
Ye Ole Survey Monument (YOSM) is a captivating series of caches that pays homage to the remarkable legacy of OutForTheHunt's YSM series (GC45CC).
YOSM caches are strategically positioned at or near Trig Points. These triangulation stations have played a pivotal role as surveying landmarks, contributing to the mapping of expansive territories.
Some of these points, bearing historical significance, might now be situated on private land or have vanished with time. As a result, the caches are artfully placed in close proximity, reverently acknowledging the historical importance of these survey monuments.
More information, bookmarks and statistics can be found at the YOSM Website
If anybody would like to expand the Ye Ole Survey Monuments Series, please do.
I would ask that you request a number for your cache first at www.yosm.org.uk
so we can keep track of the numbers and names to avoid duplication.