Everything Awesome

While out with a few clients working on night nav one of them was really struggling, his pacing and timing were very accurate. Accurate, but it appeared that he was unable to reliably follow a bearing across moorland in the dark.

His compass had a couple of bubbles in it so I gave him one of my spares which I knew was accurate and we tried again, this time I walk next to him. Encouraged small sections, encourage rechecking his bearing, etc. He was doing everything right but consistently 20, /30 m away from his destination..

I checked with him, are you carrying your mobile phone close to your compass that will have an effect with the magnetism he reassured me. No, he wasn’t

His eyes then lit up. He was carrying small battery-powered hand warmers which also had quite powerful batteries inside of them. He had them in his chest pocket but when his hands were cold he was sliding them in his gloves and of course he was holding his compass with those same gloves.

Removing those hand warmers and putting them in his bag resolved all the problems and with that one action that man can now navigate accurately.

I learnt a lesson last night.

I had never imagined I needed to check for hand warmers!

Click the Book Now link to contact us about booking one of our awesome night nav sessions

Syllabus: Navigation in a Day

Course Philosophy: Observation first, tools second. We learn to see the landscape before we learn to measure it.

09:30 – 10:00 | The Blind Walk & Observation

• The “No-Map” Start: We begin walking immediately. No maps are opened yet.
• Introductions: Building group rapport while moving.
• Active Observation: Students are prompted to describe every detail of the environment:
  • Underfoot: Heather, marsh, gravel, or rock?
  • Gradient: Are we climbing, descending, or “contouring” (staying level)?
  • Linear Features: Fences, walls, woodland edges, or tracks.
  • The “Micro” View: Distinct rocks or specific types of vegetation.

10:00 – 10:30 | Translating Sight to Paper

• The Chronological Reveal: We open the map at our current location.
• Mapping the Memory: Using the instructor’s observation notes, students match their physical journey to the symbols on the map.
• Symbology: Learning to identify roads, tracks, marshes, and water features based on what we just walked through.

10:30 – 11:00 | Distance & Movement

• The Human Yardstick: Introduction to Pacing (counting steps) and Timing (estimating time based on speed).
• Practical Calibration: Estimating and then measuring the distance to a visible feature.

11:00 – 11:30 | Tools of the Trade

• The Compass: Identifying parts (baseplate, housing, needle) and its primary purpose.
• Map-to-Ground: Using the compass to “orient” the map so it matches the real world.
• Scales: Understanding how 1:25,000 differs from $1:50,000 and how that affects our perception of distance.

11:30 – 12:00 | Interpreting the Shape of the Land

• Introduction to Contours: Understanding height and steepness through line density.
• Identifying Landforms: Visualizing and locating spurs (shoulders) and re-entrants (small valleys/gullies) in the surrounding terrain.

12:00 – 12:30 | Lunch

12:30 – 1:30 | Walking the Needle

• Taking a Bearing: Transitioning from “looking” to “measuring.” How to take a bearing from the map.
• Off-Path Navigation: Following a bearing into open terrain to reach a specific, non-obvious location.
• Group Navigation: Working collectively to stay on a line.

1:30 – 2:30 | Advanced Strategy: “The Navigator’s Toolkit”

• Handrailing: Using linear features (fences, streams) to move quickly and safely.
• Aiming Off: Deliberately aiming to one side of a target to ensure you know which way to turn when you hit a “handrail.”
• Collecting & Catching Features: Identifying “markers” to look for along the way and “stop signs” (catching features) that tell us if we’ve gone too far.

2:30 – 4:00 | Consolidation, Relocation & Journey Back

• The “Lead” Rotation: Students take turns leading legs of the journey back to the start.
• Synthesizing Skills: Combining pacing, observation, and bearings into one fluid process.
• 4:00 PM: Course Finished.

Every mountain height in the UK traces back to a small harbour in Cornwall

That is a fascinating bit of British cartographic history! It sounds like a tall tale, but it’s 100% true. When you see a map that says Ben Nevis is 1,345 metres above sea level, that “level” isn’t an average of the whole coast—it refers to one specific spot in Cornwall.

The Newlyn Datum

The “small harbour” you’re thinking of is Newlyn, near Penzance. Since 1921, Newlyn has been the home of the Ordnance Survey’s Mean Sea Level (MSL) datum.

Before this, the UK used a reference point in Liverpool, but it was found to be inaccurate due to the massive tidal range of the River Mersey. Newlyn was chosen because it sits on stable granite rock and faces the open Atlantic, making its tides more representative of the “true” sea level.

How It Works: The Great Levelling

Between 1915 and 1921, scientists took hourly measurements of the tide at Newlyn. They averaged these readings over six years to find the “mean” (average) sea level.

• The Brass Bolt: Inside a small stone hut at the end of the Newlyn pier, there is a brass bolt. This bolt represents Ordnance Datum Newlyn (ODN).
• The Chain Reaction: From that single bolt, the Ordnance Survey used “levelling” (a process of manual measurement using telescopic sights and rods) to map height across the entire country.
• The Benchmarks: They created a web of roughly 750,000 benchmarks (those little horizontal lines with an arrow ↑ˉ​ carved into old stone buildings and bridges) that all link back, link by link, to that one bolt in Cornwall.

Is it still accurate?

Technically, sea levels have risen by about 20 centimeters since the Newlyn datum was set in 1921. However, the Ordnance Survey continues to use the 1921 Newlyn mark as the “zero” point to maintain consistency. If they changed the starting point now, every map in the country would become “wrong” overnight, and every mountain height would have to be recalculated!

Fun Fact: The “Island” Exception

While every mountain in Great Britain (England, Scotland, and Wales) uses Newlyn, the islands often have their own:

• Northern Ireland uses a datum in Belfast.
• The Scilly Isles use a datum at St Mary’s.
• The Outer Hebrides have their own reference point at Stornoway.

How to Tell the Weather from Clouds

High-Level Clouds (Above 20,000 ft)

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• Cirrus: Thin, wispy “mare’s tails.” Fair now, but rain likely in 24–48 hours.

• Cirrocumulus: “Mackerel scales.” Change in weather coming.

• Cirrostratus: Thin veil, creates a halo around sun/moon. Rain/snow in 12–24 hours.

Mid Level Clouds (6,500 – 20,000 ft)

• Altostratus: Gray sheet. Steady rain/snow arriving in a few hours.

• Altocumulus: Fluffy balls. On warm mornings, signals afternoon thunderstorms.

Low-Level Clouds (Below 6,500 ft)

• Cumulus: “Cotton balls.” Small means fair; vertical growth means storms.

• Stratus: Flat gray blanket. Gloomy with drizzle or mist.

• Stratocumulus: Lumpy and dark. Storm brewing or front passing.

Dan’ger Clouds

• Nimbostratus: Dark and thick. Steady, prolonged rain.

• Cumulonimbus: Towering with anvil top. Heavy rain, lightning, and thunder.

• Wall/Shelf Clouds: Wedge-shaped. Severe winds and potential tornadoes.

Quick Tips

• Vertical Growth: Atmosphere is unstable; expect a storm.

• Dark Color: Cloud is heavy with water; rain is imminent.

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