Published Date: Sept. 26, 2024, 4:57 a.m. || Abin Prajapti 61 views

from qgis.core import (

    QgsProject,

    QgsPointXY,

    QgsPoint,

    QgsGeometry,

    QgsFeature,

    QgsVectorLayer,

    QgsWkbTypes,

    QgsDistanceArea

)

def get_start_end_points(layer, sn_value):

    start_point = None

    end_point = None

    # Filter the layer to select features with the specified sn_value

    layer.setSubsetString(f'"sn" = {sn_value}')

    for feature in layer.getFeatures():

        geom = feature.geometry()

        if geom.isEmpty():

            continue

        geom_type = geom.wkbType()

        if geom_type == QgsWkbTypes.LineString:

            points = geom.asPolyline()

            if points:

                start_point = QgsPointXY(points[0])

                end_point = QgsPointXY(points[-1])

        elif geom_type == QgsWkbTypes.MultiLineString:

            lines = geom.asMultiPolyline()

            if lines:

                start_point = QgsPointXY(lines[0][0])

                end_point = QgsPointXY(lines[-1][-1])

        elif geom_type == QgsWkbTypes.Polygon:

            rings = geom.asPolygon()

            if rings and rings[0]:

                start_point = QgsPointXY(rings[0][0])

                end_point = QgsPointXY(rings[0][-1])

    if start_point is None or end_point is None:

        print("Error: Could not determine start or end points.")

        return None, None

    return start_point, end_point

def calculate_distance_along_route(layer, sn_value):

    start_point, end_point = get_start_end_points(layer, sn_value)

    if start_point is None or end_point is None:

        return 0

    distance_calculator = QgsDistanceArea()

    total_distance = 0

    # Filter the layer to select features with the specified sn_value

    layer.setSubsetString(f'"sn" = {sn_value}')

    for feature in layer.getFeatures():

        geom = feature.geometry()

        if geom.isEmpty():

            continue

        geom_type = geom.wkbType()

        if geom_type == QgsWkbTypes.LineString:

            points = geom.asPolyline()

            if points:

                try:

                    start_index = points.index(QgsPoint(start_point))

                    end_index = points.index(QgsPoint(end_point))

                except ValueError:

                    print("Start or End point not found in the polyline.")

                    return 0

                if start_index <= end_index:

                    # Convert points to QgsPointXY

                    segment = [QgsPointXY(p) for p in points[start_index:end_index+1]]

                    total_distance = distance_calculator.measureLine(segment)

                else:

                    print("Start point is after the end point in the polyline.")

                    return 0

        elif geom_type == QgsWkbTypes.MultiLineString:

            lines = geom.asMultiPolyline()

            found_start = False

            for line in lines:

                if found_start:

                    total_distance += distance_calculator.measureLine([QgsPointXY(p) for p in line])

                    if end_point in line:

                        end_index = line.index(QgsPointXY(end_point))

                        segment = [QgsPointXY(p) for p in line[:end_index+1]]

                        total_distance += distance_calculator.measureLine(segment)

                        break

                else:

                    if start_point in line:

                        start_index = line.index(QgsPointXY(start_point))

                        segment = [QgsPointXY(p) for p in line[start_index:]]

                        total_distance += distance_calculator.measureLine(segment)

                        found_start = True

        elif geom_type == QgsWkbTypes.Polygon:

            # Handle polygon distances if needed

            pass

    return total_distance

# Load the road layer using the file path

layer_path = 'E:/Personal File/abin/pyqgis/data/BLOCK/road_sample.shp'

road_layer = QgsVectorLayer(layer_path, 'road_sample', 'ogr')

if not road_layer.isValid():

    print(f"Failed to load the road layer from: {layer_path}")

else:

    QgsProject.instance().addMapLayer(road_layer)

    # Define the sn_value to select

    sn_value = 1

    # Calculate the distance along the route

    distance = calculate_distance_along_route(road_layer, sn_value)

    print(f"Distance along the route: {distance:.2f} meters")