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I'm working with QGIS 3.10 under FreeBSD 12.1 and trying to use a North direction SVG arrow symbol which is controlled by an atlas. The atlas is driven by a set of map sheets arranged along a winding corridor.

example1

Each sheet has a fixed size and scale as well as the map is turned into a axis parallel chart by the sheet (atlas driven). For each sheet I defined a North arrow rotation parameter corresponding to map rotation ("Composer -> Item Properties -> North Arrow -> Image rotation").

example2

Unfortunately the size of the North arrow is automatically adopted for each rotation due to the corresponding rotated angular dependent bounding box ("Main Properties -> Resize Mode").

Example North Direction

example3

Example North-East Direction

example4

If I use of main "Properties -> Clip" (which I guess is the right parameter for a circular symbol which is centered an cannot be clipped), the rotation by the atlas is turned off.

Which parameter do I've to use get a rotated equal sized atlas controlled symbol under the "Composer -> Item Properties -> North Arrow" dialog.

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  • Which is the parameter that you are using to change the orientation of the maps in the Atlas?
    – Val P
    Commented Mar 13, 2020 at 8:42
  • I've calculated a turn angle (with angular range control to prevent upside-down flipping) held in the attribute table for each sheet (SHEET.ANGLE_B). The ATLAS is controlled and sorted by the SHEET.ID. And the map is turned "Item Properties->Main Properties"->"Map Rotation" -> Expression(ANGLE_B) of the coverage layer (SHEET).
    – huckfinn
    Commented Mar 13, 2020 at 13:53
  • Ok. Try removing the sinc with the map in the Image orientation of the north arrow and use the same parameter in the Rotation as a variable. I tried to replicate your issue and seems to me that using this second way the arrow doesn't change in size. You can use in the expression the variable * @atlas_featureid * to recall the page.
    – Val P
    Commented Mar 13, 2020 at 13:57
  • Thanks VAL P that works fine for me. As you supposed I the removed "Image rotation -> sync" and use ( "North Arrow" -> "Item Properties -> "Rotation" -> EXPRESSION( ANGLE_B ) to get proper result. Could you provide an answer so I can mark "solve" for the question and upvote your answer?
    – huckfinn
    Commented Mar 13, 2020 at 14:20
  • Happy that works.
    – Val P
    Commented Mar 13, 2020 at 14:51

1 Answer 1

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To solve your problem you can change the way to orientate the North arrow.

Considering that you are using a parameter to change the orientation of the pages of your Atlas, in the Item Proprieties of the north arrow, instead using the option Image Rotation > Sinc with map, try to use the option Rotation.

With the Sync with map option off, go in Rotation and here use as a variable the same parameter used for orientate the Atlas pages.

enter image description here

In the expression you can use the variable * @atlas_featureid * to recall the Atlas pages (and them ID).

In this way the north arrow change the orientation according with the page orientation without change in size.

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