Despite the century of high technology and the availability for purchase of almost any GPS navigator with a wide variety of capabilities, the need for a good, reliable and serviceable compass still exists in any more or less serious and lengthy trip.
Checking the health of the compass in the field and determining the local time from the compass in the absence of hours.
If you are in your pocket or backpack for a long time, any compass will inevitably come into contact with some metal objects. A mobile phone, a knife, a flashlight, a bowler hat or some other equipment. Such a neighborhood can adversely affect the compass’s performance, therefore, before using the compass, it is advisable to check for proper operation and accuracy.
Field compass test for accuracy.
Checking any compass for accuracy is pretty straightforward. It is easily carried out in the field and does not require much time. To carry it out, you need a compass, a watch set for local time, a plumb line (for example, a tree branch, the thinner the better) and a little patience. The error of a working compass should be within 15-20 minutes of local time.
Having stuck a plumb line or a twig in the ground, we put a checked compass nearby and determine the azimuth on the Sun using a shadow. The resulting value, in our case, is divided by 196 degrees by 15. Figure 15 is the magnitude of the rotation of the Earth or the apparent displacement of the Sun for 1 hour in degrees. Then add 1. This is a seasonal adjustment. Photographing time is April, summer time is valid in Ukraine, that is +1 to the existing standard UTC + 2.
Using simple calculations, we get the following figure: (196: 15) + 1 = 07/14. We translate the received minutes (0.07) into the time format knowing that 1 degree = 1.7 minutes of time. Therefore, we multiply 0.07 x 1.7 = 0.12. Total 14 hours 12 minutes local time. And on the watch, look at the photo above shows 14.10 minutes. General conclusion: this liquid compass is fully operational and suitable for use. In this case, we checked the compass for serviceability by determining the local time from it and using the clock as a control device.
And another, already negative example with a different compass. After the measurement procedure described above, it turned out that the compass shown in the photo below is faulty. He showed a measurement error close to 20 degrees. Accordingly, its intended use, use for orientation or movement in azimuth, can lead to completely unpredictable consequences..