Uploaded September 2026 | Updated September 2026, 1 week ago
How did the SAS navigate hundreds of miles across the featureless Sahara Desert during WW2 — without GPS, accurate maps or a reliable magnetic compass?
In this video I look at the ingenious method developed by Major Ralph Bagnold and used by the British Army, the Long Range Desert Group (LRDG) and the SAS to navigate across the Libyan Desert with remarkable accuracy.
The answer was the Bagnold Sun Compass — an ingenious non-magnetic navigation instrument that used the position of the Sun and the shadow cast by a gnomon to maintain a direction of travel.
I explain how Ralph Bagnold developed his adjustable sun compass, how Mike Sadler became an expert desert navigator, and how the LRDG and SAS worked together to carry out long-range operations deep behind enemy lines.
I also make my own working Bagnold Sun Compass from cardboard, paper and a pencil and demonstrate how it works.
The video covers:
• How the Bagnold Sun Compass works
• How to use the Sun's azimuth to set the compass
• The unusual 0–180–0 scale used on the original compass
• Why the scale runs in the opposite direction to a normal compass
• How to navigate before GPS
• Dead reckoning navigation in the desert
• The Long Range Desert Group (LRDG)
• Ralph Bagnold and Mike Sadler
• The SAS in North Africa during WW2
• How the SAS reached enemy airfields deep in the Libyan Desert
• Why magnetic compasses were unreliable in desert vehicles
• How sand dunes and detours affected dead reckoning
• Why a vehicle's normal odometer could give a misleading distance
• Bagnold's ingenious odometer wheel
The Bagnold Sun Compass was designed to allow a vehicle to maintain its direction of travel while moving, without relying on a magnetic needle. This made it particularly useful in the vast desert areas of North Africa where magnetic interference from vehicles and iron ore deposits could make conventional compasses unreliable.
I also demonstrate the important difference between the original Bagnold system and modern 0–360° azimuth readings, including how to set the compass in the morning and afternoon.
The result is a fascinating piece of forgotten WW2 navigation technology — and an example of how a simple mechanical device could allow small groups of soldiers to travel enormous distances across a seemingly featureless desert.
00:00 Intro
23:46 How to use a Bagnold Sun Compass
How did the SAS navigate hundreds of miles across the featureless Sahara Desert during WW2 — without GPS, accurate maps or a reliable magnetic compass?
In this video I look at the ingenious method developed by Major Ralph Bagnold and used by the British Army, the Long Range Desert Group (LRDG) and the SAS to navigate across the Libyan Desert with remarkable accuracy.
The answer was the Bagnold Sun Compass — an ingenious non-magnetic navigation instrument that used the position of the Sun and the shadow cast by a gnomon to maintain a direction of travel.
I explain how Ralph Bagnold developed his adjustable sun compass, how Mike Sadler became an expert desert navigator, and how the LRDG and SAS worked together to carry out long-range operations deep behind enemy lines.
I also make my own working Bagnold Sun Compass from cardboard, paper and a pencil and demonstrate how it works.
The video covers:
• How the Bagnold Sun Compass works
• How to use the Sun's azimuth to set the compass
• The unusual 0–180–0 scale used on the original compass
• Why the scale runs in the opposite direction to a normal compass
• How to navigate before GPS
• Dead reckoning navigation in the desert
• The Long Range Desert Group (LRDG)
• Ralph Bagnold and Mike Sadler
• The SAS in North Africa during WW2
• How the SAS reached enemy airfields deep in the Libyan Desert
• Why magnetic compasses were unreliable in desert vehicles
• How sand dunes and detours affected dead reckoning
• Why a vehicle's normal odometer could give a misleading distance
• Bagnold's ingenious odometer wheel
The Bagnold Sun Compass was designed to allow a vehicle to maintain its direction of travel while moving, without relying on a magnetic needle. This made it particularly useful in the vast desert areas of North Africa where magnetic interference from vehicles and iron ore deposits could make conventional compasses unreliable.
I also demonstrate the important difference between the original Bagnold system and modern 0–360° azimuth readings, including how to set the compass in the morning and afternoon.
The result is a fascinating piece of forgotten WW2 navigation technology — and an example of how a simple mechanical device could allow small groups of soldiers to travel enormous distances across a seemingly featureless desert.
00:00 Intro
23:46 How to use a Bagnold Sun Compass
