Along

This function is used identify a Point at a specified distance along a LineString.

Example

import json
from turfpy.measurement import along
from geojson import LineString
ls = LineString([(-83, 30), (-84, 36), (-78, 41)])
print(json.dumps(along(ls,200,'mi'), indent=2, sort_keys=True))

{
  "geometry": {
    "coordinates": [
      -83.460865,
      32.86781
    ],
    "type": "Point"
  },
  "properties": {},
  "type": "Feature"
}

Interactive Example

from turfpy.measurement import along, length
from geojson import LineString, Feature
from ipyleaflet import Map, GeoJSON, WidgetControl, Marker
from ipywidgets import FloatSlider

ls = LineString([(-83, 30), (-84, 36), (-78, 41)])


m = Map(center=[35.47241402319959, -80.11693954467775], zoom=5)
marker = Marker(location=[30, -83])
m.add_layer(marker)


def on_value_change(change):
    global marker
    new_point = along(ls, change["new"], "mi")
    marker.location = new_point["geometry"]["coordinates"][::-1]


style = {"description_width": "initial"}
slider = FloatSlider(
    description="Marker position:",
    min=0,
    max=length(ls, units="mi"),
    value=0,
    style=style,
)
slider.observe(on_value_change, names="value")

widget_control1 = WidgetControl(widget=slider, position="topright")
m.add_control(widget_control1)


geo_json = GeoJSON(name="Geojson", data=Feature(geometry=ls))

m.add_layer(geo_json)

m