QGIS Calculate angle between two lines

Question

I am currently trying to calculate the angle between two lines or rather vectors (which are not touching) like in the picture shown below:

In order to calculate the angle α, I think I will have to lengthen v1 somehow, so I get an intersection point of both vectors, like this:

Is there a way to do this within a python script (and how?) or can I do this with the field calculator of QGIS?

As I have two vector layers, I need this calculation more than one time and I will have to store the result into an attribute.

Answer 1

Possible first step will be azimuth calculation by the Field calculator.

degrees(azimuth(start_point($geometry), end_point($geometry)))

To obtain the angle between them, there would be several options, for instance:

• Save the attribute table as csv and calculate (v1.azimuth - v2.azimuth) by a spreadsheet software (Excel, Calc).
• SQL syntax using JOIN by Virtual layer