[Qgis-user] QGIS Atlas gymnastics

[Zoltan]

Sounds promising.
Thanks Alexandre and Roland

Now where did I put my 'do not disturb' sign.....?

Regards,
Zoltan

On 2021-10-15 11:13, Alexandre Neto wrote:
> Ah! good to see that video put to good use :-)
>
> Yes, Zoltan, all you ask seems possible to me. The secret is in the 
> way you prepare your coverage layer to iterate over the items. Check 
> the video comment as I forgot to explain one step in the video.
>
> I also have this old blog post that covers dynamic size pages. The 
> expressions are a bit outdated. that is, there are now functions that 
> make the expressions easier:
>
> https://gisunchained.wordpress.com/tag/atlas/
>
> Alexandre Neto
> QGIS Support
> www.qcooperative.net <http://www.qcooperative.net>
>
> On Fri, Oct 15, 2021 at 9:53 AM Roland Spielhofer <rspiel at gmx.net> wrote:
>
>     Hi Zoltan,
>     I guess your first item is covered here:
>     https://www.youtube.com/watch?v=NCsnTt6uxXo
>     I call the video "Atlas on steroids" ;-)
>     Regards,
>     Roland
>     *Gesendet:* Freitag, 15. Oktober 2021 um 10:39 Uhr
>     *Von:* "Zoltan" <zoltans at geograph.co.za>
>     *An:* "qgis-user" <qgis-user at lists.osgeo.org>
>     *Betreff:* [Qgis-user] QGIS Atlas gymnastics
>     Hi,
>     I wonder if someone can confirm if below is possible or not, using
>     the Atlas facilities  QGIS 3.20.3 in WIndows 10.
>
>     Two issues, the second relying on the first.
>     *#1 Variable size Map Item.*
>     I would like to vary the size of the Map Item window, depending on
>     the zoom window of the Atlas page.
>     I can set the "Position and Size" using an Expression or an
>     attribute Field, but this seems to be fixed rather than dynamic
>     ie: Is it possible to have Expression and/or Field values dynamic
>     per Atlas coverage page?
>
>     *#2 Multiple Sub-maps per MapSheet.*
>     Is it possible to have an Atlas page layout such that (say) in the
>     top half of the page you have your zoomed map (as in #1 above) and
>     in the bottom half of that sheet-page you place n-mapboxes  as
>     insets predefined as n-AOI rectangles inside the zoom-window in
>     the top of this MapPage?
>
>     *A practical example/use would be:*
>     Say you are doing an aerial analysis of a stretch of river and you
>     have identified areas of interest by placing oriented rectangles
>     around them.
>     You now want to show an overview of segments of the river, and
>     then a zoom-in to each identified AOI rectangle to show larger
>     scale prints below this river segment.
>
>     *Method could/would be to:*
>
>         Using the width of your intended page size, calculate the
>         length of river you can fit across 1 page of your Atlas. Let's
>         assume 1Km
>         Now a river meanders so you cannot run down the polyline
>         depicting the river, you need to rotate and cut the river to
>         the width of your atlas page.
>         This means your atlas Map-Item width will be constant, but the
>         height, due to curvatures in the river, will vary.
>         Once you have your oriented MBRs calculated along the river,
>         you can use these as your Atlas Coverage layer.
>         To show this with optimal page-area usage, you would need the
>         Atlas facility I describe in *#1 above*.
>
>         Now, along the river you will have pre-placed your oriented
>         AOI rectangles.
>         These will be much smaller rectangles than the 1Km
>         river-length Atlas Coverage rectangles.
>         Now, for each AOI rectangle inside the current 1Km coverage
>         rectangle, I want to show a larger scale image below the
>         current coverage rectangle.
>         If*#2 above* was possible and flexible, one could use the
>         calculated (current) bottom left paper coord of the coverage
>         rectangle to calculate the top-left position of the first AOI
>         area.
>         And so on across then down the remaining Atlas page for
>         subsequent AOI boxes, which will likely be of varying size.
>
>     I suppose this is rather like wanting an Atlas page-set within and
>     Atlas page.
>
>     Anyone achieved something like this?
>     Does this sound useful?
>
>     I guess, unless I've missed some facility in Atlas, I will be
>     doing this by using the Atlas facility to spit out carefully named
>     jpeg images, and then assembling the pages using Python and
>     LibreOffice (or something).
>
>     All thoughts/directions welcome.
>
>     Kind regards,
>     Zoltan
>
>     --
>
>     =============================================
>     Zoltan Szecsei GPrGISc 0031
>     Geograph (Pty) Ltd.
>     GIS and Photogrammetric Services
>
>     Cape Town, South Africa.
>
>     Mobile: +27-83-6004028 (Signal, not WhatsApp)
>     www.geograph.co.za  <http://www.geograph.co.za>
>     =============================================
>
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-- 

=============================================
Zoltan Szecsei GPrGISc 0031
Geograph (Pty) Ltd.
GIS and Photogrammetric Services

Cape Town, South Africa.

Mobile: +27-83-6004028 (Signal, not WhatsApp)
www.geograph.co.za
=============================================
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