Finding True North for Solar Panel Placement: A Simple Method

[Baluncore]

Three other ways.
1. Mark your exact location on a map. Look for a distant visible feature that is also marked on the map. Draw a line on the map between the two. Rotate the map so the line points at the distant feature. The map is then correctly orientated, so the map grid will be N–S at your location.

2. Use a GPS to read Lat–Long on site and somewhere that can be seen from site. Travel back and forth to check the readings are reliable. The bearing of the line between the two sites can be found from the equations for a great circle passing through those two points.

3. If you read GPS Longitude, then find a place North or South with exactly the same longitude, the line between the two will be true North–South. The further apart the points, and the more times you check the numbers, the more accurate the N–S line.

 

[Tom.G]

If you want perfection near the solstice, you can get a good west-east line by marking the shadow any time before noon, marking intervals as you observe the shadow get shorter, and then stop marking when the shadow is the same length as the original mark. The shadow traces a hyperbolic path with the apex pointing at your stick, so you just go for symmetry of the hyperbola to get your west-east line.

That's almost the simplest way. As @Anachronist stated, the apex of the hyperbola will point at the stick at local Noon. This is the same as saying that the shadow will be shortest at Noon. The shortest shadow of stick is your North-South line, and it occurs at local Noon. No need to spend the time creating the other half of the hyperbola.