[composer] Allow syncing pictures to true north (fixes #192) #3618
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Previously pictures could only be synced to grid north, which can be totally wrong for many CRSes (especially in polar areas) Users now are given a choice of grid or true north, and can also enter an optional offset to apply if eg magnetic north is instead desired. When synced to true north the bearing is calculated using the centre point of the linked map item. Fix qgis#192, qgis#4711 This fix was sponsored by the Norwegian Polar Institute's Quantarctica project (http://quantarctica.npolar.no) and coordinated by Faunalia.
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I also should note that this fixes a bug where synced north arrows are not connected to the correct slot when a project is restored, causing different rotation behaviour with restored projects vs newly created composer pictures items. |
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@nyalldawson , nice; any plans to add true-north to the north arrow canvas decorator? |
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@nirvn it's out of spec for this work, but should be quite straightforward to adapt the composer north arrow stuff to suit.... |
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Maybe we could use https://www.ngdc.noaa.gov/geomag/calculators/help/declinationHelp.html to get the declination |
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Previously pictures could only be synced to grid north, which can be totally wrong for many CRSes (especially in polar areas). To fix this users are now given a choice of grid or true north, and can also
enter an optional offset to apply if eg magnetic north is instead desired.
When synced to true north the bearing is calculated using the centre point of the linked map item.
This fix was sponsored by the Norwegian Polar Institute's Quantarctica project (http://quantarctica.npolar.no) and coordinated by Faunalia.