ancient Chinese south-pointing chariot

**Jon** · Oct 18, 2016, 01:50 PM

The south-pointing chariot was an ancient navigational tool invented in China. They were created centuries before magnetic compasses were used for navigation.

How did they work? They don't automatically point south, like a magnetic compass automatically points in a specific direction. First, the operator manually initialized the chariot by aiming its pointer southward by hand. Then, the chariot rolls along roads. As the chariot turns, it turns its southward pointer relative to its body. Let's say you're heading north, and the chariot is pointing south, behind you. You turn 90 degrees to your right, and are now heading east. The chariot pointer turns too, so that it's still pointing south. This is essentially mechanized dead reckoning.

A south-pointing chariot image from 1609:

It is believed, but not known, that south-pointing chariots generally worked by using differential gears. When the chariot moved in a straight line, both wheels turned at equal speeds, and the south-pointing figure atop the chariot did not move. When the chariot turned, the wheels rotated at different speeds, so the differential caused the south-pointing figure to rotate. There is great contention over the historical origin of the differential gear, but the south-pointing chariot offers a reasonable claim to an early use.

There are significant accuracy problems with using a south-pointing chariot as a means of navigation. First of all, irregularity of the traveled ground surface would introduce errors. Second, even a minuscule variation in the manufacture of the two wheels would introduce compounding errors in the south-pointing figure's orientation. Manufacturing processes in ancient China were not capable of producing the precision necessary to reduce this error. In addition, they could not compensate for the wear and tear of the wheels as they traveled over the ground surface. One option is that the chariot could have only been lowered to the ground when the vehicle towing it was turning.

However, as a cultural amusement, and something that may have been considered "magic" at the time, the south-pointing chariot is a fascinating part of history.

Related: Antikythera Mechanism

**Toolmaker51** · Sep 1, 2021, 08:01 PM

If I know anything, it's a bit about navigation, especially oceanic and littoral.
Nobody sensible would venture far out to sea pointing to what direction they left from. May be what limited their colonization attempts until more recently.
Dead Reckoning [DR] (from deduced) uses simple calculations, to monitor progress at regular intervals. USN DR's at half hour intervals. You are lost if electronics go down, even worse without functioning chronometer. NO matter what evolves electronically, the sextant, pelorus, stopwatch, parallel rule, plotting arm, lead pencil remain at hand. And plenty of erasers.
Great Circle plots [rhumb lines] are DR'ed weeks in advance, right down to 'intersections' where they'll schedule UNREP transfers of fuel and stores.

**mklotz** · Sep 2, 2021, 09:18 AM

I don't think it could be used at sea. It senses turns through its wheels. A turn made by the ship on which the device sits would not be registered by the wheels.

Muslims might appreciate this device since it could be used to show the Qiblah direction (effectively a mobile mihrab) as they travel about. The Chinese revere the south - the most auspicious house direction in feng shui is south-facing - so the device may have been used in a manner similar to that of the Muslims, long before Mohammed.

**Toolmaker51** · Sep 2, 2021, 11:49 AM

OOOhhh no...don't get me started on feng-shui.
We toured 27 (yes twenty-seven) homes in three business days Nov 2004, orchestrating move from SoCal to Midwest. Mrs. Toolmaker was in charge of that, I willingly appointed her as such. She scored 10-10 on entry ways, orientation, floor plans, even addresses, the whole shooting match.

Some dispute we could have done so; au' contraire! She had that feng-biz wired. Many rejected immediately, with mere opening of front door, to a sharp "NO WAY" "Pfui Teufel!" in a distinct high German accent.
Still laughing about it today, 15 years hence.

Understood that not well suited to navigation; thought was they tried to plan or record coastal headway manually or connected to helm. Even some guy towing it about like a pull toy.

**DIYSwede** · Sep 2, 2021, 12:31 PM

Originally Posted by mklotz

I don't think it could be used at sea. It senses turns through its wheels. A turn made by the ship on which the device sits would not be registered by the wheels.

Practical tip for Maritime DIY:ers:
-Unless you have the Chariot straddling the vessel amidships, its axles connected to (preferably big) paddle-wheels:
one on starboard and the other on port side, Marv!

On its precision and accuracy: YBMV! (Your Bearings May Vary),
the further its axles and paddlewheels sticks out, the better precision you'll get!

**Toolmaker51** · Sep 2, 2021, 02:25 PM

Originally Posted by DIYSwede

Practical tip for Maritime DIY:ers:
-Unless you have the Chariot straddling the vessel amidships, its axles connected to (preferably big) paddle-wheels:
one on starboard and the other on port side, Marv!

On its precision and accuracy: YBMV! (Your Bearings May Vary),
the further its axles and paddlewheels sticks out, the better precision you'll get!

Though, I perceive the limitation of accuracy would be real long axles versus curvature of Earth?

**mklotz** · Sep 2, 2021, 04:37 PM

Weld the chariot to a turntable and spin it up to 10Krpm; then you'll have something that really stays pointing in the right direction. In honor of middle Eastern fast food you can call it a gyroscope.