# How accurate is the method of finding north with a watch?

There is a method of finding north with a watch described here

So you point the hour hand of your watch at the sun. Halfway between your hour hand and the noon mark is south.

How accurate is this method of finding north?

TLDR: Its accurate at solar noon which probably won't correspond to noon on a watch and is inaccurate otherwise without more information.

Reasons for it not corresponding to noon on your watch.

• Failing to account for Daylight Savings Time
• The difference between solar time and the time zone.
• Going east or west within a timezone (solar noon is 16 minutes later on the western border of Wyoming compared to the east)

• The sun's speed across the sky is not constant, its faster at solar noon and slower at dawn/dusk.
• Equation of time, depends on the time of the year.

With all of that said, it is possible to find north using the sun with a solar compass and can be more accurate in areas with lots of iron, but in order to use one you need to know,

• Set the sun's declination for that day, obtained by means of tables, on a scale attached perpendicular to the time dial.

• Set the latitude on a scale in the alidade.

• Set the approximate local time on a dial that rotates on a polar axis.

Solar Compass

These inaccuracies are also why it is difficult to tell time other than solar noon with a compass, the direction of the sun's shadow can't directly be correlated to a time without more information.

• While finding the true north from the sun, with a watch or just from knowing the time and judging the shadows is hard to impossible, it is quite easy to learn to judge which way to go on a road or path where there are but two options.
– Willeke
Jun 28, 2018 at 14:48
• @Willeke I think you are underestimating the pedantry that goes on around here :) Yes just the sun will be useful, but its not very precised Jun 28, 2018 at 14:50
• Do you have any estimate on how inaccurate this method could be (worst case scenario etc.)? Jun 28, 2018 at 14:52
• @JeroendeK It depends on the latitude, but around 15 &deg; / 1 hour at certain times assuming you knew the correct solar time Jun 28, 2018 at 15:16
• @CharlieBrumbaugh wow that's quite a lot. Thanks! Jun 28, 2018 at 16:16

In short:
Not completely reliable but good enough for emergencies. It may give you north-east or north-west, but it will not give you south instead of north if you do it right. A compass used by an inexperienced person might send you 180 degrees off. See the last bit of this answer.

While the watch method is not good enough to find the north in an area where there are many options, like in an open field or in a forest with many roads that might go north, it has its uses and it is worth learning for emergency use.

The 'watch' method or just learning to read the shadows will help you when you are out in the wilds without a proper compass and you want to walk roughly one direction or when you are in a place where you know that the road you are on runs north-south or east-west.

The watch will work with any watch with a twelve hours system, an hours hand an a reliable 'twelve' spot.