Ho trovato questo metodo per calcolare la declinazione magnetica a partire da una semplice osservazione del sole.
Chiedo ai più esperti se si tratta di un metodo valido o meno, efficace o impreciso.
Wood Trekker: Using the Sun to Find the Magnetic Declination in Your Area
Chiedo ai più esperti se si tratta di un metodo valido o meno, efficace o impreciso.
Wood Trekker: Using the Sun to Find the Magnetic Declination in Your Area
Se fosse una applicazione fondata e non empirica sarebbe estremamente utile appuntarla, fermo restando che in contesti difficili come le montagne è praticamente impossibile avere una precisa idea del punto di orizzonte di alba e tramonto...So, how do you calculate the magnetic declination in a particular area using the sun:
Well, this is a trick I learnt from a member (Wolfy) on Blades and Bushcraft. Ready? Here it is:
Add together the azimuths of the rising and setting sun (or of the setting and rising sun) as observed during the same day (or night) at the same location. Find the difference between this sum and 360 degrees. One half of that difference will equal the amount of local declination of the compass needle.
So, what does that mean? Well, in the same day, align your compass to the North and take a measurement of the number of degrees off of North where the sun raises. Then when the sun sets, take a similar measurement by aligning the compass North and then seeing how many degrees off of North the sun sets. Add the two numbers, subtract 360 from them, and divide the result by two. That should give you the magnetic declination in the particular area.
Here is an example:
Sun rises at magnetic azimuth 65 degrees as taken with your compass.
Sun sets at magnetic azimuth 305 degrees as taken with your compass.
That equals 370 degrees. Take away the sum of the true azimuths which we know to be 360 degrees. That gives us us 10 degrees which we divide by 2, giving us the answer of 5 degrees.
If the sum of the taken azimuths is more than 360 degrees (as in the above example) the declination is to the east; if less it is to the west.