如何计算Leaflet中折线的距离，如geojson.io？ [英] How to calculate the distance of a polyline in Leaflet like geojson.io?

问题描述

我正在使用Mapbox和Leaflet处理地图，我应该让用户绘制多边形并计算并显示该多边形的数量，我还需要让用户绘制折线并显示折线的距离。

I am working on a map with Mapbox and Leaflet and I am supposed to let the user draw polygons and calculate and show the are of that polygon and I also need to let the user draw a polyline and show the distance of the polyline.

我已经找到了多边形区域功能，但我无法弄清楚如何计算折线的距离。

I have figured out the polygon area feature but I cannot figure out how to calculate the distance of a polyline.

我的代码如下：

loadScript('https://api.tiles.mapbox.com/mapbox.js/plugins/leaflet-draw/v0.2.2/leaflet.draw.js', function(){
    loadScript('https://api.tiles.mapbox.com/mapbox.js/plugins/leaflet-geodesy/v0.1.0/leaflet-geodesy.js', function(){
        var featureGroup = L.featureGroup().addTo(map);

        var drawControl = new L.Control.Draw({
        edit: {
            featureGroup: featureGroup
        },
        draw: {
            polygon: true,
            polyline: true,
            rectangle: false,
            circle: false,
            marker: false
        }
    }).addTo(map);

    map.on('draw:created', showPolygonArea);
    map.on('draw:edited', showPolygonAreaEdited);

    function showPolygonAreaEdited(e) {
        e.layers.eachLayer(function(layer) {
            showPolygonArea({ layer: layer });
        });
    }
    function showPolygonArea(e) {
        var type = e.layerType,
        layer = e.layer;

        if (type === 'polygon') {
            featureGroup.clearLayers();
            featureGroup.addLayer(e.layer);
            e.layer.bindPopup(((LGeo.area(e.layer) / 1000000) * 0.62137).toFixed(2) + ' mi<sup>2</sup>');
            e.layer.openPopup();
        }

        if (type === 'polyline') {
            featureGroup.clearLayers();
            featureGroup.addLayer(e.layer);
            // What do I do different here to calculate the distance of the polyline?
            // Is there a method in the LGeo lib itself?
            // e.layer.bindPopup(((LGeo.area(e.layer) / 1000000) * 0.62137).toFixed(2) + ' mi<sup>2</sup>');
            e.layer.openPopup();
        }

    }
    });
});

LGeo lib本身有一个方法可以帮我计算折线的距离吗？ geogson.io 上的开发人员也有办法计算距离，但我似乎无法弄清楚他们的代码。我不是一个经验丰富的Javascript开发人员。欢迎任何帮助。 ：）

Is there a method in the LGeo lib itself which will help me calculate the distance of the polyline? The devs at geogson.io also have a way to calculate the distance but I cannot seem to figure it out looking at their code. I am not a seasoned Javascript developer. Any help is welcome. :)

推荐答案

所以我终于想出了一个算法。我基本上找到了折线的属性，它保存了折线的所有 latlngs ，然后我让它经历一个循环，我用 distanceTo 来自Leaflet的方法来计算点之间的距离，并继续将它们添加到 totalDistance 变量。

So I finally came up with an algorithm myself. I basically found the property of the polyline which holds all the latlngs of the polyline and then I made it go through a loop and I used the distanceTo method from Leaflet to calculate distance between points and kept on adding them to a totalDistance variable.

if (type === 'polyline') {
    featureGroup.clearLayers();
    featureGroup.addLayer(e.layer);

    // Calculating the distance of the polyline
    var tempLatLng = null;
    var totalDistance = 0.00000;
    $.each(e.layer._latlngs, function(i, latlng){
        if(tempLatLng == null){
            tempLatLng = latlng;
            return;
        }

        totalDistance += tempLatLng.distanceTo(latlng);
        tempLatLng = latlng;
    });
    e.layer.bindPopup((totalDistance).toFixed(2) + ' meters');
    e.layer.openPopup();
}

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