Allow map rotation by compass

[rinigus]

Suggested in view and followMe modes

See http://talk.maemo.org/showpost.php?p=1557461&postcount=705

[sbridger]

adding a few more:
compass on bike
tristate button
calibration
Mentions compass current drain. Magnetic sensor chips are very low power sensors, so would need to test real current drain before assuming that this is true.
[Tested with Chargemon and OrienteeringCompass in Flight Mode, location=off, with both apps showing live tiles. Current drain does not appear to change with orienteeringcompass app paused or closed i.e. I don't think compass adds current drain.]

Magnetic compass calibration also needs to consider magnetic declination (20degrees here now). I can't see one in Sailfish->location->settings. How is the magnetic compass supposed to work?
Seems you would need to know local declination to show correct bearing. As an alternative / automation to a setting, this site seems to calculate and return json or other data formats
https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#declination

[rinigus]

Looking into how to implement it and already first simple tests are very encouraging. Would have to include https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml? into Pure Maps, as we have location data available as well.

[rinigus]

Limiting the issue to compass support, no orientation by hand. If there is an interest in hand-based orientation of the map, open issue separately.

[rinigus]

Now just need to add magnetic declination calculations. Looks like have to get some extra lib for it as Qt Position supports it from 5.4

[rinigus]

Implemented rotation by compass, closing.

[sbridger]

Entering compass declination manually is also OK.
I will test as soon as there is a release for me to test.

Sadly the XA2 sfos gps and compass performance is practically unusable.

The major issue for me is that the GPS will get a lock under clear sky, unreliably in a car, and simply cannot get a lock at all under moderate tree cover (over a 1/2 hour period -zero positions. It does get enough signal to get ephemeris or maybe its using network, as it shows satellite plot). (sfos3.3)

By comparison my winphone 640 locks in 5 seconds with no network in the same positions.

A secondary issue is that the compass drifts terribly (3.2, haven't tried with 3.3 yet), and was unusable. I added declination to the compass app, but didn't do more with it when I found how much it drifted.

[rinigus]

On my device, lock may take some time, but when locked it seems to work fine. Compass works quite well too. Note that for compass, I have developed new hardware adaptations which are submitted for review and, hopefully, will be merged in the near future. I hope it will help XA2 as well