I am trying to determine the angle between two intersecting lines. However, I need the angle to be from the start point of line1 to the start- or end-point of line2 - whichever is the next point going in a counter-clockwise direction around the circle's perimeter (see diagram at bottom of question).
My steps so far have been:
1) I found the intersection points and saved them to a point file
2) I created a 10cm buffer around the points (0.1 metres)
3) I clipped line1 and line2 to the buffer
4) I calculated the start- and end-points of line1 and line2 as:
with arcpy.da.UpdateCursor("line", ('X0a','Y0a','X1a','Y1a', "SHAPE@")) as cursor:
for row in cursor:
row = row.firstPoint.X
row = row.firstPoint.Y
row = row.lastPoint.X
row = row.lastPoint.Y
5) I created separate fields and calculated their values as:
dx = !X1a!-!X0a!
dy = !Y1a!-!Y0a!
r = math.sqrt(math.pow(!dx!, 2) + math.pow(!dy!, 2))
ra = math.sqrt(math.pow(!dxa!, 2) + math.pow(!dya!, 2))
c = math.asin(abs((dxdya - dydxa))/(r*ra)) / math.pi * 180
c is the angle between the points, however, it is not always the angle I need. I need the angle from a point on line1 to the nearest point on line2 going counter-clockwise around the circle's perimeter.
There is probably a really easy solution for this, but, I just haven't been able to figure it out. Any help is greatly appreciated.
I am using ArcGIS 10.2.