Pi and More

06.05.10

Using the Sun as a Natural Compass

With the help of my application, the Advanced Geocaching Tool, the Nokia N900 becomes a near perfect geocaching device. However, there are three things lacking:
  • The built-in gps is not as accurate as a standalone receiver.
  • You have to protect the device from water, dirt and drops.
  • It doesn't have an electronic magnetic compass.
The first thing is said to improve somewhat with the coming firmware update.

The second point can be compensated with a good protective case. I use this arm strap from rungps.net. This way I always have my hands free and the N900 is protected from dirt and rain.

There's little we can do about the third point, the lack of a magnetic compass. When you're standing still, the device can not know in which direction you are moving. Even when you're moving, it can only guess the current viewing direction. Hence, when you're standing somewhere and want to know where to go next, you first have to move in any direction. That doesn't sound too bad, but wait until you're standing somewhere in a steep hillside.

To compensate for the lack of the magnetic compass, AGTL now includes a "sun compass" feature. Whenever the sun should be visible (i.e. during daytime), AGTL shows a small round sun in the compass view - see image. The sun's position is calculated using the current time and the position (both from the last GPS fix).

Geocaching on the N900 using the sun as a natural compass

When you align the sun's direction with the icon's position, the other directions (north direction and geocache location) are guaranteed to be correct.

Unfortunately, it can't help you when clouds are blocking the sunlight... but who goes geocaching then anyways?
Kommentar schreiben
  • Bugs in AGTL bitte hier melden.
    Please report any bugs in AGTL here.
  • Wer eine Antwort erwartet, sollte eine echte E-Mail-Adresse angeben.
    If you expect a reply from me, please provide a working e-mail address.
  • Ich kann keine individuelle Problemlösung zu Websicherheit oder regulären Ausdrücken geben!
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