3

I have this function to get the intersection point of line and a polygon. How to find the vertices of the polygon(red dots marked in the image) edge where the line intersects using shapely? I have managed to find the nearest point using shapely nearestPoint function.

enter image description here

# get the intersection point.
def checkIntersection2(polyX, polyY, linePtX, linePtY):
    poly = LineString([(x, y) for x, y in zip(polyX, polyY)])
    line = LineString([(x, y) for x, y in zip(linePtX, linePtY)])
    intPoints = poly.intersection(line)
    return intPoints
4

You need to iterate through the edges of the LinearRing of the polygon

from shapely.wkt import loads
lin = loads('LineString (289.63171806167395061 -200.22555066079294761, 380.69030837004402201 -65.28898678414094547)')
pol = loads('Polygon ((112.23259911894263041 -229.94933920704846742, 178.75726872246687549 -113.4132158590308137, 309.44757709251092592 -114.35682819383258391, 376.44405286343607031 -230.42114537444933831, 305.67312775330390195 -344.59823788546259493, 176.39823788546246419 -345.07004405286346582, 112.23259911894263041 -229.94933920704846742))')
# the LinearRing
from shapely.geometry import LineString
polin = LineString(list(pol.exterior.coords))
# intersection 
pt = polin.intersection(lin)
print(pt.wkt)
POINT (327.0268317294637 -144.8110298888352)

Now using Determine if Shapely point is within a LineString/MultiLineString (using the answer of Mike T using the distance with an appropriate threshold because there are floating point precision errors when finding a point on a line)

# iterate through the edges to determine if Shapely point is within
points = list(polin.coords)
for i,j in zip(points, points[1:]):
   if LineString((i,j)).distance(pt) < 1e-8:
       print(i,j)
(309.4475770925109, -114.35682819383258) (376.44405286343607, -230.42114537444934)

Control

enter image description here

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.