Time of Day

Excerpts from Finding Directions without a Map or a Compass,
from the U.S. Armed Forces Survival Manual, Edited by John Boswell,
published by Rawson, Wade Publishers, Inc., New York, 1980.

Time of Day Using the Shadow Tip Method

 

Being able to establish time of day is important for such purposes as keeping a rendezvous, carrying out prearranged concerted action by separated persons or groups, estimating the remaining duration of daylight, and so forth. Shadow-clock time is closest to conventional clock time at midday, and the spacing of the other hours, compared to conventional time, varies somewhat with the locality and the date.

To find the time of day, move the stick to the intersection of the east-west line and the north-south line, and set it vertically in the ground. The west part of the east-west line indicates 6 a.m., and the east part is 6 p.m., anywhere on earth.

 

The north-south line now becomes the noon line. The shadow of the stick is an hour hand in the shadow-clock, and with it you can estimate time using the noon line and the 6 o'clock line as your guides. Depending on your location and the season, the shadow may move clockwise or counterclockwise, but this does not alter your manner of reading the shadow-clock.

 

The shadow-clock is not a timepiece in the ordinary sense. It makes every day twelve unequal "hours" long, and always reads 6 a.m. at sunrise and 6 p.m. at sunset. However, it does provide a satisfactory means of telling time in the absence of properly set watches.

 

If you have a watch, the shadow-clock can be used to "store up" the direction you obtained by using the shadow-tip method. Merely set your watch to shadow-clock time and then use the "watch method" described below. This avoids the ten to fifteen minute wait required to complete a shadow-tip reading for true direction, and thereby permits you to take as many instantaneous readings as are necessary to avoid "circling." After traveling for an hour or so, take a check shadow-clock reading and reset your watch if necessary. The direction obtained by this modified watch method is the same as that obtained by the regular shadow-tip method using a stick. That is, the degree of accuracy of each method is identical.

 

Direction, Using a Watch

 

A watch can be used to determine approximate true north or south. In the north temperate zone only, the hour hand is pointed toward the sun. A south line can be found midway between the hour hand and 12 o'clock. If on daylight saving time, the north-south line is found midway between the hour hand and one o'clock. 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 in the afternoon.

 

The watch may also be used to determine direction in the south temperate zone; however, the method is different. The 12 o'clock hour dial is point4ed toward the sun, and halfway between the "12" and the hour hand will be a north line. If on daylight saving time, the north line lies midway between the hour hand and "1." The temperate zones extend from latitudes 23.5 degrees to 66.5 degrees in both hemispheres.

The watch method can be in error, especially in the lower latitudes, and may cause "circling." To avoid this, make a shadow-clock and set your watch to the time indicated. After traveling for an hour take another shadow-clock reading. Reset your watch if necessary.