William Mudge's Ordnance Survey Map Man

Mist, bogs,

no trees, no tracks, hardly a recognisable feature on the landscape.

This is Dartmoor, the most difficult place to navigate in the whole of Britain.

But imagine trying to cross this place without any maps.

A few hundred years ago, that was the challenge facing an intrepid team of

map makers who laid the foundations for today's Ordnance Survey maps.

One of their earliest surveys took place here in Devon, and the reason for it was war.

In 1793, France had declared war and invasion seemed imminent.

The Army desperately needed maps to plan for the nation's defence, so who would take on a that massive task?

Step into the breach, Lieutenant Colonel William Mudge,

the man who would lead the Ordnance Survey to greatness.

What I want to know is, are Mudge's maps truly accurate?

Was defence really their only purpose?

And can these classic maps be used to navigate across the modern British landscape?

The first edition of the Ordnance Survey

was the product of the most complete mapping exercise of Britain since the Tudors.

For the first time in our history, there were maps linking county to county which covered the entire land

based on a scale of one inch to the mile.

The OS as we know it was the creation of Devonian William Mudge,

who in 1791, was a 29 year-old lieutenant put in charge of this epic mapping survey.

The end of the 18th century was a bad time for Britain.

The American colonies had just been lost and Napoleon's forces were sweeping across Europe.

French spies had already surveyed southern England's vulnerable beaches

and harbours and Napoleon's fleet was on standby to attack Britain's red-coated troops.

One unlikely landing point - Ilfracombe, on Devon's north coast.

The story goes that the women of the town took matters into their own hands.

Removing their red petticoats, they draped them around their shoulders

and paraded on that hill over there and on the fields around the harbour.

These British femme fatale hoped that by creating cliffs of crimson,

the French Navy would think they were facing the British Redcoats. And it worked.

The French sank a couple of Ilfracombe boats.

But faced with what seemed to be the vanguard of the Redcoat Army,

they thought better of landing and sailed away.

Quite a force to be reckoned with, those Ilfracombe ladies!

This near miss was an alarming wake-up call and so, two centuries ago,

mapping Britain's invasion coasts became a top priority.

I'm going to make a journey all the way across Devon

from Ilfracombe on the north coast to Start Point on the south coast.

I'll be following in the footsteps of Mudge's surveyors, crossing treacherous sea channels, dealing

with a maze of lanes and confusing countryside and navigating my way across the bleak heights of Dartmoor.

And my journey's end, Devon's invasion beaches.

Responsibility for mapping the entire country fell to the Board of

Ordnance, set up to supply the Army and maintain national defences.

Their map survey began by accurately measuring a single line, then plotting two

more lines to make a triangle, then using these three lines to be the basis for three more triangles.

And so on. Once Mudge had created this network of huge interconnecting

triangles, the second and third surveys filled in the grid.

Then, after this third stage, the finer features like roads, rivers

and bays were mapped and added to the triangulated grid.

I'm going to follow in Mudge's footsteps by surveying the strategic Skerne Bay at Appledore.

I'll be assisted by the Royal Engineers, whose predecessors helped on the original survey.

We'll be using equipment from that era.

No modern gadgets like GPS or laser sights for us.

First, we need to establish where we are in the bigger picture in relation to one of Mudge's known trig points.

I'm going to conduct what's called a closed traverse survey and it works like this.

I'm standing at Appledore right here and I can see a bay curving around

roughly like this to a headland over here.

With the help of the Royal Engineers, I'm going to place a series of staffs

at intervals around the edge of the bay. I'm going to measure the distances between those staffs

and the angles between them until I get to the very end of the bay here where the headland is.

From there, I take a final angle reading back across the bay

to my first staff here and close the traverse. I can then draw my map.

Let's put this theodolite together.

Lance Corporal Anderson is dispatching his men.

First, staff bearer John, to move from position A, to position B.

Then, the measuring team to determine the distances between the sightingstaffs

with an antique set of precision chains.

If you walk along it every 10ft or so,

there will be a marker telling you the actual distance from the end.

But you've got to pull it tight first?

-Yes, it's got to be mega tight.

-I'm using a 200 year-old theodolite

and the first angle I'm taking is from north round to Mudge's trig point

at the telegraph pole on Fort Hill.

And the reading of that...

283.

Now, to take our second reading.

These first two positions are critical

to fix and lock all our readings to fit in with Mudge's original grid.

And that is 113.

We've got to move the theodolite to where the staff man is on point B.

But leaving the staff man here

-and then we'll move John further on.

-It sounds complicated, but it's dead simple really, isn't it?

If you're not completely accurate, then nothing will tie in.

So you've just got a load of maps that are just basically drawings. No use to man nor beast.

-So a map becomes a drawing if you've got a mistake in it?

-Yes, exactly.

The task facing Mudge's men on the detailed survey

to map every feature of the landscape, seems impossibly daunting.

Finally, to close the traverse across the other side of the bay.

This time, I turn around and measure back to where we started.

-Is John still there?

-Look at the left-hand side window

and just come down from the left-hand side edge of that window.

Got him.

Final reading, back to our very first staff is 75.

That's it. Closed a traverse.

We've now surveyed the entire bay, double-checked the first and last positions.

It's taken hours.

Just imagine what it was like doing the entire coast.

A nice cup of tea.

The scale of Mudge's surveying achievement is mind-boggling.

Once finished, Mudge's priority was to get the maps published and distributed as fast as possible.

This is not a pretty map.

It's undecorated, uncoloured and it doesn't even have a border on it.

It's entirely a practical and totally utilitarian, functional military map.

It's drawn to a scale of one inch to the mile.

It's the optimum scale for the human eye to absorb a vast expanse of landscape.

The most important thing a military man needs to know

is the relief - the hills, valleys and after that the communications.

The hills are very, very clearly shown by hashers.

These hashers might look like ordinary black lines but they're not.

They're thinner at each end and thicker in the middle. They're also wiggly.

It's to give an impression of a hill starting on a gentle gradient,

steepening and then flattening out on top of the hill.

The rivers between them are very clearly marked and the river valleys, so you get an immediate

impression of what bits of landscape are going to be easy to march across,

where you could set an ambush, where you might expect enemy troops to approach in from the coast.

This is primarily a road map.

The turnpike roads are shown with a thicker black line on one side of the other.

The ordinary country roads are shown as a pair of parallel lines, the same density of ink on both sides.

The smallest roads of all, the unfenced ones, are shown with a very thin pecked line along each side.

Although this is, of course, a military map, the surveyors

who made it couldn't resist including some non-military features.

Down here in the southern part of Dartmoor, we've got some Bronze Age hut circles here.

An ancient cross up here.

Down here, there's some Bronze Age barrows - it's a chink in the armour

of this relentlessly military survey - a hint at what this map would eventually become.

In the long run, the OS map would become the standard for military and civilian alike.

Tomorrow, I plan to test out just how accurate the surveying team were back

in the early 1800s, before I take on a really difficult challenge.

Crossing Dartmoor.

I'm climbing Codden Hill.

It's the most dramatic viewpoint in this part of North Devon.

It was also one of the triangulation points used by Mudge during his survey.

It's easy to see why.

I can see all the way south, over the Taw valley to the heights of Dartmoor, 25 miles away.

I'm going to try and stay as close as possible to this long red straight line on Mudge's map.

On the way, I'm going to try and locate a number of small and fairly obscure features.

It's going to be a real test of Mudge and a real test for me.

Before setting off, I've arranged to meet archaeologist Candy Hatherley

to help me look for clues in interpreting Mudge's map.

If I was going to make a journey across this map,

and I wanted to pick up particular features marked on it which may have disappeared over the last 200 years,

what are the kind of clues I'd be looking for?

For structures, for example, something like a mill.

If you went to the river, you may see a dam or a weir running to the mill.

When you've got to the structure itself, there would be a mill or farmhouse.

There may be stones left, the stone walls may be remaining.

If not, there may be a lump in the ground. A piece of raised ground.

So if you see an anomaly in the landscape, a path to nowhere, something like that,

then you know that there could be a feature there that's disappeared.

Potentially. Looking from the map, the map evidence shows something on site and then you go there

and there's nothing remaining, but you have these clues.

The evidence that's leading towards the structure that's actually no longer there on the ground.

Mudge's map was a snapshot of the landscape of the time.

But 200 years later, lots will have changed.

Buildings will have crumbled, forests expanded or contracted,

all conspiring to make my task more difficult.

But not as difficult as Mudge's men found their part in the surveying project.

Armed with the latest surveying equipment they stood out in the sleepy part of the country.

They were challenged and threatened by locals who mistook them for French spies.

Unfortunately, their outfitters had made their uniforms the same shade of blue as the French Army.

So the surveyors were obliged to carry warrants that explained who they were and what they were doing.

But my mission is to spot-check the features on the red line

which crosses a track running through a wood.

Inside the wood, the line meets a water mill which sits by a river.

First real test of this map, and I'm not sure whether it's going to pass or not,

is whether I can find the track running beside this small wood and field.

The field I think I'm in right now.

The trouble is this is a very large wood.

It might have got much bigger over the last two centuries and I can see

absolutely no sign whatsoever of a track.

I think I'm going to have to take a closer look.

Well, now I'm in this wood, things are starting to look up for the map.

These trees are youngish conifers

and they haven't been here for that many years.

The wood has clearly got much, much bigger since 1809.

This looks good.

This is what looks like

an old track and also the woods change.

This is a broadleaf wood and, look at this, there's a stump here of an old broadleaf tree.

So this is a very old wood. The trackway is very clear.

We've got an embankment on this side.

High bank on that side, and just over there, is the field that it should be running beside.

And a track, so that's right.

Now for that mill which should be near a river.

I've been in this wood for ages.

But I'm starting to think that I must have wandered off course.

What's this? Look at this.

There's a ford. This ford is on the map.

So now I know where I am.

So, having overshot and gone slightly off course,

I've turned around to head back up the valley.

If I go back up the valley and here's the mill leat,

the mill leat should be a channel full of water that fed the mill.

The key to finding the mill, which may not have withstood the ravages of time, is finding the leat.

A man-made channel which would have fed it with water.

Eureka, water.

This might look like a woodland stream, but it isn't, it's man-made.

It's an old canal running parallel with the contours along the hillside.

I'll eat my umbrella if there's not a mill up there.

I can't believe it. There's a wall crossing the mill leat here.

Look.

Why is that wall crossing the mill leat if it's not part of the mill?

This part of the leat's trebled in size, it's massive.

There's a huge pool here, or was.

This is the mill. You can't see much now.

It looks just like a boggy puddle, but this is definitely the mill. Just where the map said it would be.

It doesn't do to doubt Mudge, it really doesn't.

So, Mudge has delivered among the thickly wooded hills of North Devon.

But tomorrow is another day.

And a much more daunting and dangerous one for his map and for me.

I'll be facing the ultimate test - alone on the featureless and expansive wilderness of Dartmoor.

This is Dartmoor.

Yesterday was a successful day for my straight line test of the map, but Dartmoor is a bleak and testing

landscape, dotted by occasional granite outcrops called tors.

It's a notoriously unfriendly training ground for Britain's fighting forces.

So how well was it mapped by Mudge?

There's something gone wrong with the map up here.

The tor's in the right place but the moor each side doesn't correspond with the map.

I can't believe that much is wrong, but something's not right.

I'm going to have to go and take a closer look at the moor.

The problem on the map is that

it shows a stream that seems to circle the whole of High Willows, turning it into an island.

There's no such thing of a river that goes in a full circle ahead of a river that joins its own tail.

Well I've reached the bed of the river valley on the east side of the tor.

Not much water to be seen, but there is a line of reeds flowing down the valley in that direction.

You can clearly see the two slopes of the valley, just as the map says.

No sign of water.

I can hear water though.

Yes, down here.

There's water under the ground.

I can feel it. It's quite deep water.

Its fast-flowing. Look at that,

flowing that way.

So, if I follow the reeds in that direction against the flow of the water,

with a bit of luck, I'll find out what the problem is with this map.

I've followed the river bed for as far as I can.

But it's just run out.

Instead of a river, there's a great mountain of moorland in the way.

If that river really existed, there'd have to be a 100ft deep ravine right where I'm standing. But there isn't.

There's just this huge ridge of moorland.

I've never, ever seen such a huge mistake on an Ordnance Survey map.

Mudge's surveyors got it really badly wrong.

It was hardly surprising.

Dartmoor's landscape is riddled with bogs, peat swamps and false summits.

On top of that, the moor can play strange tricks on the relative

heights of large features, or where the horizon is, or even which way's up.

Oh, and then there's the weather.

Before I go any further, I've arranged to meet Colonel Tony Clark,

Commandant of Okehampton Camp here on Dartmoor.

He's trained forces personnel on the moor for over 20 years.

So if anyone can tell me what's going on up here, it should be him.

Why is it that Dartmoor has such a terrible reputation for navigation?

Well when they produced this map, the points on which they did

their surveying were quite a long distance apart.

I think there was one over here on Cosden Beacon

and the next one was right over here on the far side of the moor.

So in between, the room for mathematical area was quite great.

When they were doing the trigometrical surveys, if they found an error, they shoved it into a big

open space and Dartmoor is mapped at a lower scale than the surrounding area because there's nothing to see.

So this is to do with the lowest level of accuracy up here than there

-would be for the farmland around the edge of the moor.

-Absolutely right.

The town and country planning maps are of a greater accuracy than the

ones you get here or indeed in the Highlands of Scotland.

How do you recommend I travel using this old map?

Use a compass because at least if you're using a compass, you're going to be roughly on the right bearing.

But, that's also going to give you probably the worst route.

So, you're going to want to have your compass as a back-up and follow around the shape of the land.

That way, you will find it by far the easiest way to get through.

You can get into some difficulties here - the bogs, the mires as we call them.

If your first footstep goes up to your ankle

and your second footstep's up to your knee, then make sure your third step's backwards.

Right. I'll remember that.

Colonel, thank you very much. I feel cautiously optimistic.

Any final word of advice before I set off into the murk?

Pray.

Thank you very much. Colonel Clarke is sure that we can

trust the accuracy of the high points on the map.

So I'm going to use the hilltops as markers on a route across this wasteland.

From the summit of Dartmoor, High Willows to Lints Tor to Great Nieset

and thence to Cranmere Pool.

Cranmere Pool is the most remote point on Dartmoor.

The isolation of Cranmere Pool has given it almost mythical status and as it means,

the pool frequented by cranes, I feel particularly drawn to it.

Let's hope that I can frequent it myself well before nightfall.

Now, the distance from where I am now to Lints Tor is...

..one-and-a-quarter inches,

so at this scale of map, that makes it one-and-a-quarter miles.

The direction is pretty much due south. So if I use my antique compass

I can find that

Lints Tor

must be that black outcrop sticking up on the crest of the hill down there.

You're not just timing yourself over a measured distance to make sure you don't overshoot, but you're also

trying not to deviate from your bearing which means going straight through bogs like this one here.

If the bog's too deep or wide, you can make a detour around the outside of it.

But then you've got to somehow regain your bearing on the far side

and the risk is that you miss your landmark at the far end.

This is Great Niset.

I've got nine-tenths of a mile to go to get to Cranmere Pool across

the huge undulating, boggy plateau. Cranmere Pool's just a tiny puddle.

My navigation's going to have to be spot on if I'm not going to get lost.

It's going to take about 28 minutes.

The weather's closing in, it's cold, windy and it'll be dark soon.

I really don't want to spend a night out.

I'm continually being

thrown off course and so as I'm walking along, I'm trying to compute

how many minutes to add on

to my...the 28 minutes I'd estimated to cover the...

nine-tenths of a mile.

Well, my watch says...

two and a half minutes. Well, that's so close now that I ought to start looking

around here for Cranmere Pool.

I think I can see a little glint of light.

I'm hoping this might be it.

It is.

This, believe it or not, is Cranmere Pool.

The pool frequented by cranes.

It's not a lake,

it's not even a pool.

You couldn't even have a bath in it.

That's Cranmere Pool.

What an amazing place!

Mudge's map brought me safely across this desolate landscape here to Cranmere Pool.

Wilderness like this is almost unknown in England.

But let's not forget that Mudge's main mission was a military one and that included our vulnerable

invasion beaches so that we could defend ourselves from the French.

Made it! Start Point!

There's the English Channel, France is over there and that

great sweeping arc of sheltered water is Start Bay, the soft underbelly of South West England.

Start Bay has a series of the most perfect invasion beaches in the South West.

Mudge's pioneering work meant that the British could at last

face the threat of foreign invasion from a position of strength.

Secure in the knowledge of finally knowing their own backyard.

And it was only by knowing every nook and cranny of the land, that England could be defended. Thanks to Mudge.

The French never did invade.

Mudge's military maps went on to open up the countryside for the people.

Our modern Ordnance Survey maps are direct descendants of Mudge's vision.

Britain mapped in its entirety - a legacy to the nation.

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