How do smartphones work out what direction they are pointing?

A typical smart phone has three magnetic field sensors, fixed perpendicular to each other, which are used to work out the local direction of Magnetic North.

In addition, they have three accelerometers which sense gravity to give tilt information and to help work out which way is down.

Three steps to your true path

1. Magnetic and gravity field sensors located within your phone measure the direction of Magnetic North and the downward direction at the phone's location (Figure 1).

2. Using the GPS coordinates of the phone location and a global map of declination angle (the angle between true north and magnetic north) the application software computes the required correction angle for True North (Figure 2).

3. The map or image shown to the user can now be correctly orientated to True North, which is what most people expect (Figure 3).

The application software uses the location of the phone from the mobile phone’s nearest base-station or from a GPS reading along with a map of the declination of the magnetic field (produced by BGS and NOAA in the USA) to work out the direction of True North at the user's location.

Why is it important?

The declination angle is small in the UK (< 2°) but can be much larger in California (~15°) or in Brazil (> 20°). Users in these areas would quickly become lost if the application software didn’t correct for declination.

Pour être informé des derniers articles, inscrivez vous :

Mélina 07/11/2017 15:39

Bonjour. très bel article. très intéressant. un beau blog. n'hésitez pas à visiter mon univers. lien sur pseudo. à bientôt. bises

Angeline 06/11/2017 16:15

j'aime me promener sur votre blog. un bel univers. vous pouvez visiter mon blog (cliquez sur pseudo) à bientôt.

Angelilie 08/09/2017 18:59

beau blog. un plaisir de venir flâner sur vos pages. une belle découverte et un enchantement.N'hésitez pas à venir visiter mon blog (lien sur pseudo)
au plaisir

Angelilie 10/06/2017 16:10

toujours un plaisir de flâner sur vos pages. au plaisir de revenir. N"hésitez pas à visiter mon blog. lien sur mon pseudo. à bientôt.