Leaflet和TurfJS:无法使用目标和方向角绘制垂直线

var map = L.map('map').setView([51.505, -0.09], 13);
L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
  attribution: 'Map data &copy; <a href="https://www.openstreetmap.org/">OpenStreetMap</a> contributors',
  maxZoom: 18,
}).addTo(map);

var targetPoint = L.marker([51.5, -0.09]).addTo(map);
var directionLine = L.polyline([[51.5, -0.09], [51.51, -0.1]], {color: 'red'}).addTo(map);

var targetCoord = targetPoint.getLatLng();
var directionCoord = directionLine.getLatLngs()[1];

var perpendicularLine = turf.lineString([[targetCoord.lng, targetCoord.lat], [directionCoord.lng, directionCoord.lat]]);
var perpendicularLineWithLength = turf.lineOffset(perpendicularLine, 0.01, {units: 'kilometers'});

var perpendicularLineLatLngs = perpendicularLineWithLength.geometry.coordinates.map(function(coord) {
  return [coord[1], coord[0]];
});

var perpendicularLineLeaflet = L.polyline(perpendicularLineLatLngs, {color: 'blue'}).addTo(map);