[Qgis-user] Visualising crossfall in trajectory

[Charles Dixon-Paver]

I stand corrected, there is a backgrounds/background_square.svg included in
the default svgs, so you can probably just use that and adjust the width to
height ratio to get the desired effect.

On Mon, 2 Nov 2020 at 18:57, Charles Dixon-Paver <charles at kartoza.com>
wrote:

> I would suggest using an embedded SVG marker, for which you can set data
> defined properties for width and height.
>
> I don't think there is a straight line/ block marker, but you can
> probably find one somewhere using the resource sharing plugin.
>
> Alternatively, you can make a custom SVG in inkscape and get it "qgis
> ready" using the script at
> https://github.com/zacharlie/fonts4gis/blob/master/parameterise.py
>
> I have one that's semi-suitable online ready, but with rounded edges, at
> https://github.com/zacharlie/svg4qgis/blob/master/svg/TN.svg
>
> Perhaps test with that and see if you have any luck. Otherwise, I can help
> make one for you if you have trouble with inkscape or the processing
> script, but more information of what you want it to look like would help.
>
> As for your expression, from what I can gather you are looking for a
> nested if statement or case expression:
>
> ```
> CASE
> WHEN ("crossfall"<0) THEN "heading"-90
> WHEN ("crossfall">0) THEN "heading"+90
> ELSE 0 END
> ```
>
> Or:
>
> ```
> if("crossfall"<0,"heading"-90,
> if("crossfall">0,"heading"+90,0
> ))
> ```
>
> This is assuming your fields are using the correct datatypes, although
> there are expressions for changing them.
>
> Hope that helps
>
> On Mon, 2 Nov 2020 at 18:27, Roland Spielhofer <rspiel at gmx.net> wrote:
>
>> Hi,
>> I have a trajectory of a vehicle (= a list of points including heading,
>> crossfall, slope, curvature, radius, ...) and would like to visualise the
>> crossfall. Per point there should be a line pointing left or right
>> (transverse to driving direction) with the line having a length according
>> to the quantity of the crossfall and pointing to left if negative, to right
>> if positive.
>>
>> I have tried font marker - an arrow to visualize heading which works
>> well. But with the crossfall I struggle.
>>
>> The font marker may be not the right joice, as it makes the lines not
>> only longer, but also thicker.
>> What type of marker would right for this? Should just be a simple line
>> that alters in length according to crossfall
>>
>> How would the expression look like to handle the case crossfall<0 ->
>> heading-90; crossfall>0 -> heading+90
>>
>> Any help appreciated!
>> TIA
>> Roland
>>
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