Cfrtjryk

I need to find distance in eastward direction from each point to the closest polygon edge:

I can find shortest distance in any direction with:

pointlayer = QgsProject.instance().mapLayersByName('points_inter_squares')[0]

points = [[f.geometry(),f['Ruta_100km']] for f in pointlayer.getFeatures()]



squarelayer = QgsProject.instance().mapLayersByName('squares')[0]

squares = [[f.geometry(),f['Ruta_100km']] for f in squarelayer.getFeatures()]



for point in points:

    print(min([QgsGeometry.distance(point[0],square[0]) for square in squares if point[1]!=square[1]]))



>>12639.380321901293

>>3320.150455611874

>>6650.862023710273

>>2452.079442886869

'Ruta_100km' is the Squares IDs, so I measure distance to all Squares but the one intersecting the Points.

Is there a method where I can specify direction when measuring distance?

A general solution: Provided a grid described by its origin (x0, y0) and a grid spacing d_grid (100km in your example), the problem reduces to calculate the difference between the test points p = (x, y) x-coordinate and the x-coordinate of the N-S grid line lying next to p, x_square, so the question is, what is x_square:

The following does not need a grid layer, but only the description of the grid as described above:

for p in points:

    # assumption: grid origin (x0, y0), spacing d_grid

    # metric coordinate system

    y = p.geometry().asPoint().x()

    # calculate y-distance to origin

    dx0 = x - x0

    # calculate number of square in which p(x, y) lies (2 in the example)

    square_count = int(dx0 / d_grid) + 1

    # calculate x-coordinate of N-S grid line next to p

    x_square = x0 + d_grid * square_count

    # calculate the desired distance

    dp = x_square - x

    print(dp)

Based on the comment from @Michael Stimson I managed to solve this by creating a line extending east, intersecting this with the polygons, finding min x coord of the resulting line(s) and subtracting this minx-startx. It should also work with irregular shaped polygons. It requires having polygon ids on the points (for example by intersecting them) to exclude any polygon directly intersecting the point.

pointlayer = QgsProject.instance().mapLayersByName('points_inter_squares')[0]

points = [[f.geometry(),f['Ruta_100km']] for f in pointlayer.getFeatures()]



squarelayer = QgsProject.instance().mapLayersByName('squares')[0]

squares = [[f.geometry(),f['Ruta_100km']] for f in squarelayer.getFeatures()]



max_search_distance = 200000



for geom, pointid in points:

    startx, starty = geom.asMultiPoint()[0]

    endx = startx+max_search_distance

    line = QgsGeometry.fromPolyline([QgsPoint(startx,starty), QgsPoint(startx+max_search_distance,starty)])

    intersections = [QgsGeometry.intersection(line,square[0]) for square in squares if (pointid!=square[1] and QgsGeometry.intersects(line,square[0]))]

    minx = min([l.asPolyline()[0][0] for l in intersections], default=startx) #If no feature is found, set minx to startx which will give 0 distance when subtracting

    print(minx-startx)