diff --git a/js/rtree/rbush-knn.js b/js/rtree/rbush-knn.js
new file mode 100644
index 0000000..f3803fc
--- /dev/null
+++ b/js/rtree/rbush-knn.js
@@ -0,0 +1,156 @@
+/* https://github.com/mourner/rbush-knn */
+
+(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.knn = f()}})(function(){var define,module,exports;return (function(){function r(e,n,t){function o(i,f){if(!n[i]){if(!e[i]){var c="function"==typeof require&&require;if(!f&&c)return c(i,!0);if(u)return u(i,!0);var a=new Error("Cannot find module '"+i+"'");throw a.code="MODULE_NOT_FOUND",a}var p=n[i]={exports:{}};e[i][0].call(p.exports,function(r){var n=e[i][1][r];return o(n||r)},p,p.exports,r,e,n,t)}return n[i].exports}for(var u="function"==typeof require&&require,i=0;i<t.length;i++)o(t[i]);return o}return r})()({1:[function(require,module,exports){
+'use strict';
+
+var Queue = require('tinyqueue');
+
+module.exports = knn;
+module.exports.default = knn;
+
+function knn(tree, x, y, n, predicate, maxDistance) {
+    var node = tree.data,
+        result = [],
+        toBBox = tree.toBBox,
+        i, child, dist, candidate;
+
+    var queue = new Queue(undefined, compareDist);
+
+    while (node) {
+        for (i = 0; i < node.children.length; i++) {
+            child = node.children[i];
+            dist = boxDist(x, y, node.leaf ? toBBox(child) : child);
+            if (!maxDistance || dist <= maxDistance * maxDistance) {
+                queue.push({
+                    node: child,
+                    isItem: node.leaf,
+                    dist: dist
+                });
+            }
+        }
+
+        while (queue.length && queue.peek().isItem) {
+            candidate = queue.pop().node;
+            if (!predicate || predicate(candidate))
+                result.push(candidate);
+            if (n && result.length === n) return result;
+        }
+
+        node = queue.pop();
+        if (node) node = node.node;
+    }
+
+    return result;
+}
+
+function compareDist(a, b) {
+    return a.dist - b.dist;
+}
+
+function boxDist(x, y, box) {
+    var dx = axisDist(x, box.minX, box.maxX),
+        dy = axisDist(y, box.minY, box.maxY);
+    return dx * dx + dy * dy;
+}
+
+function axisDist(k, min, max) {
+    return k < min ? min - k : k <= max ? 0 : k - max;
+}
+
+},{"tinyqueue":2}],2:[function(require,module,exports){
+(function (global, factory) {
+typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
+typeof define === 'function' && define.amd ? define(factory) :
+(global = global || self, global.TinyQueue = factory());
+}(this, function () { 'use strict';
+
+var TinyQueue = function TinyQueue(data, compare) {
+    if ( data === void 0 ) data = [];
+    if ( compare === void 0 ) compare = defaultCompare;
+
+    this.data = data;
+    this.length = this.data.length;
+    this.compare = compare;
+
+    if (this.length > 0) {
+        for (var i = (this.length >> 1) - 1; i >= 0; i--) { this._down(i); }
+    }
+};
+
+TinyQueue.prototype.push = function push (item) {
+    this.data.push(item);
+    this.length++;
+    this._up(this.length - 1);
+};
+
+TinyQueue.prototype.pop = function pop () {
+    if (this.length === 0) { return undefined; }
+
+    var top = this.data[0];
+    var bottom = this.data.pop();
+    this.length--;
+
+    if (this.length > 0) {
+        this.data[0] = bottom;
+        this._down(0);
+    }
+
+    return top;
+};
+
+TinyQueue.prototype.peek = function peek () {
+    return this.data[0];
+};
+
+TinyQueue.prototype._up = function _up (pos) {
+    var ref = this;
+        var data = ref.data;
+        var compare = ref.compare;
+    var item = data[pos];
+
+    while (pos > 0) {
+        var parent = (pos - 1) >> 1;
+        var current = data[parent];
+        if (compare(item, current) >= 0) { break; }
+        data[pos] = current;
+        pos = parent;
+    }
+
+    data[pos] = item;
+};
+
+TinyQueue.prototype._down = function _down (pos) {
+    var ref = this;
+        var data = ref.data;
+        var compare = ref.compare;
+    var halfLength = this.length >> 1;
+    var item = data[pos];
+
+    while (pos < halfLength) {
+        var left = (pos << 1) + 1;
+        var best = data[left];
+        var right = left + 1;
+
+        if (right < this.length && compare(data[right], best) < 0) {
+            left = right;
+            best = data[right];
+        }
+        if (compare(best, item) >= 0) { break; }
+
+        data[pos] = best;
+        pos = left;
+    }
+
+    data[pos] = item;
+};
+
+function defaultCompare(a, b) {
+    return a < b ? -1 : a > b ? 1 : 0;
+}
+
+return TinyQueue;
+
+}));
+
+},{}]},{},[1])(1)
+});