Source code for turf.along._along

from turf.helpers import point
from turf.bearing import bearing
from turf.destination import destination
from turf.distance import distance
from turf.invariant import get_coords_from_geometry, get_coords_from_features
from turf.utils.exceptions import InvalidInput
from turf.utils.error_codes import error_code_messages
from turf.utils.helpers import truncate

[docs]def along(line, dist, options=None): """ Takes a LineString and returns a Point at a specified distance along the line :param line: input LineString :param dist: distance along the line :param options: optional parameters [options["units"]="kilometers"] can be degrees, radians, miles, or kilometers :return: Point `dist` `units` along the line """ if not options or not isinstance(options, dict): options = {} if not isinstance(dist, (float, int)) or dist < 0: raise InvalidInput(error_code_messages["InvalidDistance"]) coords = get_coords_from_features(line, ["LineString"]) travelled = 0 for i in range(len(coords)): if dist >= travelled and i == len(coords) - 1: break elif travelled >= dist: overshot = dist - travelled if not overshot: return point([truncate(coord, 6) for coord in coords[i]]) else: direction = bearing(coords[i], coords[i - 1]) - 180 interpolated = destination(coords[i], overshot, direction, options) return interpolated else: travelled += distance(coords[i], coords[i + 1]) return point([truncate(coord, 6) for coord in coords[-1]])