Method signedArea

src/common/mapping/WebMapV2.js:3222–3230

(ring)

    }

    signedArea(ring) {
      let sum = 0;
      for (let i = 0, len = ring.length, j = len - 1, p1, p2; i < len; j = i++) {
        p1 = ring[i];
        p2 = ring[j];
        sum += (p2[0] - p1[0]) * (p1[1] + p2[1]);
      }
      return sum;
    }

    _getTdtLabelLayerName(layerId) {
      return `${layerId}-tdt-label`;