turf.js绘制的自交多边形的OpenLayers3相交误差

Question

我使用OpenLayers3 ol.interaction.Draw让用户在地图上绘制一个形状，或者单击顶点，或者通过Shift+Drag绘制一个自由形状的多边形(这对我的应用程序很重要)。绘制完形状后，我使用turf.js将绘制的形状与客户端中的WFS层进行比较，运行intersect()以查看WFS功能是否与绘制的形状相交。但是，如果手绘形状具有最小的自交，则turf.js intersect()函数将发生以下错误(第326行是我调用intersect()的地方)。

turf.min.js:9隐身物体 getResultGeometry @ turf.min.js:9 si.overlayOp @ turf.min.js:9 交集@ turf.min.js:15 e.exports @ turf.min.js:16 (匿名函数)@ main.js:326

下面是我的代码草图。

var features = new ol.Collection();

var vs = new ol.source.Vector({
  format: new ol.format.GeoJSON(),
  url: function(extent) {
    return XXXXXX;
  },
  strategy: ol.loadingstrategy.bbox
});

features.on('add', function() {
  vs.forEachFeatureIntersectingExtent(extent, function(feature) {
    // use to turf.js to intersect each feature with drawn feature
    var bt = gjformat.writeFeatureObject(feature, {rightHanded: false});
    var dt = gjformat.writeFeatureObject(features.item(0), {rightHanded: false} );

    var intersection = turf.intersect(bt, dt);
  }
});

我试图同时使用turf.js simplify()和ol.geom.Geometry.simplify()，但都没有效果。有没有人建议让turf.js intersect()来处理手绘的自交多边形？还是一种在运行交叉口之前删除自交点的方法？

Answer 1

受Using JSTS buffer to identify a self-intersecting polygon答案的启发(感谢领导，@ahocevar)，我将解决方案移植到了turf.js上。使用自交0缓冲绘制的特性，移除较小的、自相交的多边形，并为您留下一个干净的特性，以便在intersect()中运行。

    features.on('add', function() {
      vs.forEachFeatureIntersectingExtent(extent, function(feature) {
        // create geojson of wfs features and drawn feature
        var bt = gjformat.writeFeatureObject(feature, {rightHanded: false});
        var dt = gjformat.writeFeatureObject(features.item(0), {rightHanded: false} );

        // check for kinks in the drawn feature
        var kinks = turf.kinks(dt);
        var dtf;

        if(kinks.features.length > 0) {
          // if there are self-intersections, buffer by 0 to get rid of them
          dtf = turf.buffer(dt, 0, 'meters');
        } else {
          // if there are no self-intersection, intersect by unbuffered features
          dtf = dt; 
        }

        var intersection = turf.intersect(bt, dtf);
      }
    });

Answer 2

您至少可以提醒用户注意自交。这些都可以用JSTS检测到。见Google Maps Polygons self intersecting detection。删除自交比较困难，但是使用JSTS：Using JSTS buffer to identify a self-intersecting polygon也应该是可能的。