流星：用两点搜索最近的游乐设施

Question

我正在构建一个汽车共享应用程序并设置游乐设施，我的数据库中有这种插入：

    {
        "_id": "YyPpkCDhTKStGw6CL",
        "authorId": "W6zvbcqit4Mw6a2iK",
        "stages": [
            {
                "caption": "Paris, France",
                "type": "Point",
                "coordinates": [
                    2.3522219000000177,
                    48.856614
                ]
            },
            {
                "caption": "Lyon, France",
                "type": "Point",
                "coordinates": [
                    4.835659,
                    45.764043
                ]
            },
            {
                "caption": "Toulouse, France",
                "type": "Point",
                "coordinates": [
                    1.4442090000000007,
                    43.604652
                ]
            }
        ],
    }

阶段按要求的顺序列出（巴黎 -> 里昂 -> 图卢兹）。然后我有一个带有两个输入的简单表单（start 和 end）。我的问题是：如何找到最近的乘车点？

看来我必须做那样的事情:

在以下位置查找游乐设施：

stages.X 附近开始
stages.Y 接近结束
X < Y

你知道如何进行这样的查询吗？

Answer 1

我发现了一个奇怪的方法来完成这项工作，这里是：

// Set up of arguments and scope
var from =  [2.3522219000000177, 48.856614];
var to =    [4.835659, 45.764043];
var maxDistance = 2000; // in meters

// First, find ids where rides are near my "from" point
var ids = Rides.find({
    stages: {
        $near: {
            $geometry: {
                type: 'Point',
                coordinates: from,
            },
            $maxDistance: maxDistance,
        }
    }
}, {
    fields:{
        _id:1
    }
}).map(function(item){return item._id;});

// Then, find rows which are near my "to" point BUT restricting it to my ids found above
var results = Rides.find({
    _id: {$in: ids},
    stages: {
        $near: {
            $geometry: {
                type: 'Point',
                coordinates: to,
            },
            $maxDistance: maxDistance,
        }
    }
});

// Foreach the rows to filter the case where I match the points in the wrong order
var filtered = [];
results.forEach(function(row){
    var distFrom = [];
    var distTo = [];
    _(row.stages).each(function(stage){
        distFrom.push(calcDistance(stage.coordinates, from));
        distTo.push(calcDistance(stage.coordinates, to));
    });

    var nearestFrom = _.indexOf(distFrom, _.min(distFrom));
    var nearestTo = _.indexOf(distTo, _.min(distTo));

    if(nearestFrom < nearestTo)
        filtered.push(row);
});

// My final results!
console.log(filtered);

以及计算两点间距离的函数：

calcDistance = function(p1, p2){
    var R = 6378137; // Earth’s mean radius in meter
    var dLat = rad(p2[0] - p1[0]);
    var dLong = rad(p2[1] - p1[1]);
    var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
        Math.cos(rad(p1[0])) * Math.cos(rad(p2[0])) *
        Math.sin(dLong / 2) * Math.sin(dLong / 2);
    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    var d = R * c;
    return Math.round(d); // returns the distance in meter
}

流星：用两点搜索最近的游乐设施

Meteor: Search the nearest ride with two points

javascript

mongodb

geojson

meteor