The earth’s relationship to the sun can help you to determine direction on earth. The sun always rises in the east and sets in the west, but not exactly due east or due west. There is also some seasonal variation. In fact, depending on the season and where you are, the sun could rise and set up to 50 degrees off of true east and west.
Shadows will move in the opposite direction of the sun. In the Northern Hemisphere, they will move from west to east, and will point north at noon. In the Southern Hemisphere, shadows will indicate south at noon. With practice, you can use shadows to determine both direction and time of day.
Local Apparent Noon.
Exactly half-way along its daily journey, the sun will be directly south of an observer (or north if the observer is in the Southern Hemisphere).
It is at this point that shadows will appear their shortest.
The time at which this occurs is referred to as “local apparent noon.”
Exactly half-way along its daily journey, the sun will be directly south of an observer; it is at this point that shadows will appear their shortest; known as “local apparent noon.”
NOTE: This rule may not apply to observers in the tropics (between 23.5 degrees north and south latitude) or in the polar regions (60 degrees latitude).
Whenever using any type of shadow casting device to determine direction, “local apparent noon” (or the sun’s highest point during the day) must be known. Local apparent noon can be determined by the following methods.
Knowing sunrise and sunset from times.
If sunrise is 0630 and sunset is 1930, take the total amount of daylight (13 hours), divide by 2 (6 hours 30 minutes), and add to sunrise. Based on this example, local apparent noon would be, 0630 + 6 hours 30 minutes = 1300.
Using the string method.
The string method is used to find two equidistant marks before and after estimated solar noon. The center point between these two marks represents local apparent noon. (see the String Method and Pocket Navigator section below)
This technique will achieve a cardinal direction within 10 degrees of accuracy if done within two hours of local apparent noon. This technique may be impractical near the polar regions as shadows tend to be very long; similarly, in the tropics shadows are generally very small. This technique can also work at night using lunar illumination.
Shadow Stick Method of direction finding
Push a stick vertically into the ground.
Place a marker (stone/stick/etc) at the end of the shadow. This first shadow mark is always west—
After 10-15 minutes place another marker at the end of the shadow. This mark will represent East.
A line drawn from the first marker through the second will be a approximate west-east line.
Place your toes on the west-east line. Stand with the first mark (west) to your left and the second mark (east) to your right — you are now facing north. This is true
This method is more accurate when taken over a hour by adding markers at the shadow tip every 10-15 minutes.
Shadow Stick method
An alternate method using the shadow stick is more accurate but requires more time. Set up your shadow stick and mark the first shadow in the morning. Use a piece of string to draw a clean arc through this mark and around the stick. At midday, the shadow will shrink and disappear. In the afternoon, it will lengthen again and at the point where it touches the arc, make a second mark. Draw a line through the two marks to get an accurate east-west line.
You can also determine direction using a common or analog watch—one that has hands. The direction will be accurate within 5-8 degrees if you are using true local time, without any changes for daylight savings time. Remember, the further you are from the equator, the more accurate this method will be.
Using a watch to get a North/South line
If you only have a digital watch, draw a clock face circle on paper, or ground, with the correct time on it and use it to determine your direction at that time.
To find north-south line using your watch:
In the Northern Hemisphere, hold the watch horizontal and
point the hour hand
at the sun. In the Southern Hemisphere,
point the 12-o’clock mark
at the sun.
Bisect the angle between the hour hand and the 12-o’clock mark to get the north-south line.
If there is any doubt as to which end of the line is north, remember that the sun is in the east before noon and in the west after noon.
If your watch is set on daylight savings time, use the midway point between the hour hand and 1 o’clock to determine the north-south line.
during the period of the midsummer equinox for your area.
The 24-hour clock method.
Another method is called the 24-hour clock method. Take the local military time and divide it by two. Imagine this result to now represent the hour hand. In the Northern Hemisphere, point this resulting hour hand at the sun, and the 12 will point north. For example, it is 1400 hours. Divide 1400 by two and the answer is 700, which will represent the hour. Holding the watch horizontal, point the 7 at the sun and 12 will point north. In the Southern Hemisphere, point the 12 at the sun, and the resulting “hour” from the division will point south.
Hand Span Method
The sun crosses the meridian (imaginary north/south line) every day at noon (local apparent noon). During this time, the earth has revolved 360° over 24 hours. Therefore, the sun travels from east to west at a speed of 15° per hour (360° / 24 hours = 15°). To find north, note the current time and plot the sun from its present position backward or forward, as the case may be, to its noon position.
For example, if it is 3pm, north will be found at noon, so (15° x 3 hours = 45°) from the sun’s current position, which would require two hand spans to locate (22° + 22° = ~45°).
The diagram below will give you a general indication of measuring degrees using your hand span. You can experiment with this method and increase accuracy by measuring sun movement with your hand and then measuring it with a compass for comparison.
Hand-span method of measuring sun movement by degrees
The only material required is a small piece of cardboard or other flat-surface material, a watch, a pen or pencil, and a 1 to 2 inch pin or nail.
Set this tiny rod upright on your flat piece of material so that the sun will cause it to cast a shadow. Mark the position where the base of the rod sits so it can be returned to the same spot for later readings. Place the navigator flat on level ground. Secure the navigator from wind by placing rocks on it. Write the date and mark the tip of the shadow.
As the sun moves the shadow-tip moves. Make repeated shadow-tip markings every 15 minutes. As you make the marks on the tip of the shadow ensure that you write down the time.
At the end of the day, connect the shadow-tip markings. The result will normally be a curved line. The arch will be less pronounced closer to the vernal or autumnal equinoxes (March 20 and September 23). If it is not convenient or the situation does not permit to take a full day’s shadow-tip readings, your observation can be continued on the following day by orienting the pocket navigator on the ground so that the shadow-tip is aligned with a previously plotted points.
The markings made at the sun’s highest point during the day, or solar noon, is the north—south line. The direction of north should be indicated with an arrow on the navigator as soon as it is determined. This north-south line is drawn from the base of the rod to the mark made at solar noon. This line is the shortest line that can be drawn from the base of the pin to the shadow-tip curve.
To use your pocket navigator, hold it so that with the shadow-tip is aligned with a plotted point at the specified point. i.e.; if it is now 0900 the shadow-tip must be aligned with that point. This will ensure that your pocket navigator is level. The drawn arrow is now oriented to true north, from which you can orient yourself to any desired direction of travel.
The pocket navigator will work all day and will not be out of date for approximately one week.
A quick note about the reviews on this site: I am an affiliate for every product I review. The vendors of these products give me them without charge in order for me to test them. However all my reviews are done as honestly as possible and I make no promises to the vendor prior to writing my review. Should you click a link on this site that takes you to a paid product this link will be an affiliate link and I will be paid a percentage of the sales price should you decide to purchase that product.