The built-in $length function will only get you the 'horizontal' length along the line, not the true length allowing for the slope. To calculate this:
Take your vector layer you created using 'Points to path' and use 'Explode lines'. This will split your single line into multiple lines with breaks located at every vertex.
On this new layer, open field ...
I think the rule would be to use vector that are digitized for the specific scale you will use, for exemple Natural Earth dataset is available at 1:10m, 1:50m, and 1:110 million scales with varying level of detail, you would choose the one that is closest to your intended scale use.
By looking at your picture I would said your first picture is at a too ...
Did you consider this: Natural Earth II is a raster map dataset that portrays the world environment in an idealized manner with little human influence? Can be combined with the regular vector data form Natural Earth.
How about something like:
array_contains(string_to_array("Class", ','), '2')
This splits the string in the field "Class" into an array and returns true if the array contains the given value ('2'). This will give you all the features that contain the class/integer 2 (and leave out 12).
With the release of QGIS 3.8 there is new feature to generate raster MBTiles layers. Once the layer you want to convert is setup, you can open up the Toolbox by either selecting the gear icon or by going into the processing tab on the menu bar and selecting toolbox. Then in the Processing Toolbox, drill-down into the Raster Tools section. Within this ...
For QGIS 3 go to the Layers Properties => Attributes Form => choose your field with geometry values (in example, area) => type $area in the Defaults value box and check Apply default value on update.
This also could be usefull: $perimeter, $y, $x, $id
This should work:
you create a line (make_line), starting at the point with your fixed coordinates (created with the command make_point(25.906543, -80.546800)) and ending at the second point, defined with $geometry as the current point of your layer. You then measure the length with the ...
After you defined symbol, just add the following line immediately after to create a gradient brush style:
So it looks like:
# Create symbolfiller from properties
symbol = QgsFillSymbol.createSimple(props)