Author Topic: Magnetic declination model  (Read 1426 times)

Offline alf

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Magnetic declination model
« on: December 10, 2015, 10:38:58 »
Hello

Please, what is the origin of the magnetic declination shown by Locus in the compass window?
Does Locus uses (for example) the latest World Magnetic Model (WMM2015) to establish the declination?
Is the magnetic declination data stored on the phone for offline use ?
Does it update the model automatically (for example in 2020 with WMM 2020) when the Android device is online ?


Thanks for your help and best regards

Alf
 

Offline menion

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Re: Magnetic declination model
« Reply #1 on: December 10, 2015, 10:45:43 »
Good day Alf,

Locus use internal system build-in inside Locus, so on most devices it will be mentioned WMM 2010!

You may read about used method here: http://developer.android.com/reference/android/hardware/GeomagneticField.html . In description is information that model may be updated, but which one is currently used in your device, is not known.
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Offline poutnikl

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Re: Magnetic declination model
« Reply #2 on: December 10, 2015, 17:47:38 »
I remember a manual for a compass bought some 30 years ago, with declination table for various places. It was within -1..+1 degree range across the former Czechoslovakia, as the magnetic pole was for this region just behind the North pole.

Now it makes 4 degrees for this region, according to Locus.
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Offline menion

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Re: Magnetic declination model
« Reply #3 on: December 10, 2015, 18:20:12 »
yep, declination is changing over time. On some places faster, on some slower. I'm anyway not sure (can't remember now some knowledges from school), how exactly is declination computed from these models, so it's question if it's just simple interpolation, or model contain some time-based parameters. Anyway let's hope, that Google keep latest available model in latest versions of Android ;).
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Offline poutnikl

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Re: Magnetic declination model
« Reply #4 on: December 10, 2015, 20:33:54 »
Note that I am well aware of declination is changing, I have not wanted to imply Locus computes it wrong.. :-)
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Offline menion

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Re: Magnetic declination model
« Reply #5 on: December 10, 2015, 21:02:39 »
I understand, no worry :). If there will be an bigger changes than speed of Android (Google) updates, I may write this system manually, but I believe it won't be necessary.
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Offline alf

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Re: Magnetic declination model
« Reply #6 on: December 22, 2015, 15:53:43 »
Many thanks for your reply.

I understand that Locus uses the magnetic declination model integrated in the Android version of the device.

Suggestion for future Locus versions:
Give the possibility to the user to load in Locus the latest model data file (by just copying the coefficient file to some subdirectory of the Locus directory).
The coefficient file is tiny (5 KB) and can be downloaded by the user from "http://www.ngdc.noaa.gov/geomag/WMM/wmm_ddownload.shtml"
In this way, even old devices with old versions of Android will be able to be up to date concerning the magnetic declination.

Merry Xmas and happy new year
 

Offline menion

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Re: Magnetic declination model
« Reply #7 on: December 23, 2015, 07:41:44 »
Good day Alf, thanks for suggestion and nice end of year to You too.
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