Where do you start with a topic on Numbers? There are an infinite number of possible ways of approaching it. Including Infinity. Then I happened to look out of my front window and saw the milestone at the end of my road and on the top is an Ordnance Survey mark. Well, that’s as good a place to start as any other.
Why it was called Ordnance Survey (OS)? It seems it has its origins in 1747 when King George II commissioned a military survey of the Scottish highlands following the Jacobite revolt of 1745. William Roy was the engineer responsible for this pioneering work; one of the staff involved was noted artist Paul Sandby. The survey was produced at a scale of 1 inch to 1000 yards.
Roy’s surveying parties of about eight relied on simple surveying compasses to measure the angles, and chains up to 50 feet long to measure distance between important features. Much of the rest was sketched in by eye. Nevertheless, the map was a powerful tool as part of a broader strategy to open up access to the Highlands.
The fact that Roy was just 21 years old with no military commission when he started the survey makes his achievements even more extraordinary. His work paved the way for modern surveying and he understood the strategic importance of accurate maps. At the time of his death in 1790 his vision of a national survey for Britain was almost within reach.
It was not until 1790 that the Board of Ordnance (a predecessor of part of the modern Ministry of Defence) began a national military survey starting with the south coast of England in anticipation of a French invasion. So that’s where Ordnance came from.
By 1791, the Board had purchased the new Ramsden theodolite, and work began on mapping southern Great Britain using a baseline that Roy himself had previously measured and that crosses the present Heathrow Airport.
In 1801 the first one-inch-to-the-mile (1:63,360) map was published, detailing the county of Kent, with Essex following shortly after. The Kent map was published privately and stopped at the county border while the Essex maps were published by Ordnance Survey and ignore the county border setting the trend for future Ordnance Survey maps.
During the next twenty years roughly a third of England and Wales was mapped at the same scale. It was gruelling work: Major Thomas Colby, later the longest serving Director General of Ordnance Survey, walked 586 miles in 22 days on a reconnaissance in 1819. In 1824, Colby and most of his staff moved to Ireland to work on a six-inches-to-the-mile (1:10,560) valuation survey. The survey of Ireland was completed in 1846.
Colby designed specialist measuring equipment, established systematic collection of place names, and reorganised the map-making process to produce clear, accurate plans. But Colby the perfectionist also travelled with his men, helped to build camps, and arranged mountain-top feasts with huge plum puddings at the end of each surveying season.
One interesting fact is that the mean sea level at Newlyn in Cornwall ( calculated between 1915 and 1921 ) is the reference point for the height data on OS maps.
Here are a couple of numbers from OS today:
‘While the public still knows us for our comprehensive range of printed leisure maps, the digital side of the business accounts for more than 90% of turnover.
All 243,241 square kilometres of Great Britain are surveyed and up to 20,000 changes are put into the database daily.’
‘While the public still knows us for our comprehensive range of printed leisure maps, the digital side of the business accounts for more than 90% of turnover.
All 243,241 square kilometres of Great Britain are surveyed and up to 20,000 changes are put into the database daily.’
Reading the Map
with more creases than contours
from when I didn’t need glasses
for the red dot
of a branch line station
where the edge of my compass
would be a straight path
92 degrees true north
but as arrows aligned
latitude and longitude dissolved
and I was lost
in sounds of train doors slamming
sometimes just mine
the weight of a rucksack
blasts of wind and sun
and rain and green
my sort of heights
the smell of black coffee
from a flask
sweat
shadows on a track
back to the pub
too small to be marked
where they once knew my name
and those of friends
I haven’t seen in years.
First published in Reach, July 2025
with more creases than contours
from when I didn’t need glasses
for the red dot
of a branch line station
where the edge of my compass
would be a straight path
92 degrees true north
but as arrows aligned
latitude and longitude dissolved
and I was lost
in sounds of train doors slamming
sometimes just mine
the weight of a rucksack
blasts of wind and sun
and rain and green
my sort of heights
the smell of black coffee
from a flask
sweat
shadows on a track
back to the pub
too small to be marked
where they once knew my name
and those of friends
I haven’t seen in years.
First published in Reach, July 2025
Thanks for reading, Terry Q.























