Brainstorm

electronic compass

Posted on 2010-01-31 09:34 UTC by Sascha Riedinger. Status: Under consideration, Categories: Location & Navigation, Programming, Devices.

As we all know the N900 has no electronic compass, but for some applications like astronomy apps and augmented reality it could be very useful to have the possibility to determine in which direction the device is facing.

Especially for astronomy programs like stellarium it would be advantageous that the compass also works if the device isn't in line with the horizontal level (or if it's possible the accelerometer data has to be used to calculate the right data)

An additional device must have a clamp etc to fixate on the N900. A electronic compass needs to be calibrated, with a clamp that asserts same alignment every time it is used the calibration process must be done only once.

Thread in the forum

Solutions for this brainstorm

Solution #1: using GPS

Posted on 2010-01-31 09:34 UTC by Sascha Riedinger.

the user has to walk in one direction until with the data drom GPS the facing direction could be determined.

this is more a workaround, not a real solution.

After the initialisation process the accelerometers should be used to calculate the angle of torsion. Because at slow movement there is nearly no acceleration it could be difficult to implement this azimuth direction angle, the altitude angle should be possible.

Solution #2: electronic compass via USB

Posted on 2010-01-31 09:45 UTC by Sascha Riedinger.

it should be possible to build a extension for a electronic compass that can be plugged into the USB port.

A possible device for that would be the CMPS03 electronic compass from Devantech and a USB-I2C adapter.

How interference-prone is such a device? It uses Hall-Sensors, so any magnetic or metall in the proximitry can influence the data?
What happens if the device isn't in an angle parallel to the ground? (Maybe the accelerometer data can be used to calculate the rigth values if the CMPS03 can't do that by itself)

Solution #3: using a 3d compass via USB

Posted on 2010-01-31 10:36 UTC by Sascha Riedinger.

instead of using a CMPS03 (which only measures two axis) a 3D-compass can be used. A possible device is the MK3Mag which is also used in the MikroKopter (a flying a quadrotor helicopter)

Solution #4: 3D compass mounted in the battery cover talking via the SD port

Posted on 2010-08-30 21:56 UTC by Tiago Estill de Noronha.

as described in http://talk.maemo.org/showthread.php?t=60387

(lemme know if i need to write the details here instead of just linking to the thread)

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