用turf.js求多个点的外包多边形

Posted 2022-11-10 牛老师讲GIS

概述

最近有个需求就是求多个点的外包多边形，看了下turf.js可以实现，在此记录分享一下。

实现后效果

实现

可以通过两种方式实现：turf.convex和turf.tin，turf.convex可直接计算结果，turf.tin稍微麻烦一点，先创建不规则三角网，再通过turf.union合并得到结果。下面通过ol做一示例。

// 通过geojson获取features
function getFeatures(geojson) 
    let features = (new ol.format.GeoJSON()).readFeatures(geojson);
    features.forEach(f => 
      f.setGeometry(f.getGeometry().transform('EPSG:4326', "EPSG:3857"))
    )
    return features

// turf.convex
 fetch('./data/college.geojson').then(res => res.json()).then(res => 
    let features = [...getFeatures(res)]
    res = turf.convex(res);
    features = [...features, ...getFeatures(res)]
    vectorSource.addFeatures(features)
  )

// turf.tin
 fetch('./data/college.geojson').then(res => res.json()).then(res => 
    let features = [...getFeatures(res)]
    res = turf.tin(res)
    res = res.features
    let _res = res.shift()
    while (res.length > 0) 
      const r = res.shift()
      _res = turf.union(_res, r)
    
    features = [...features, ...getFeatures(_res)]
    vectorSource.addFeatures(features)
  )