根据对数和距离计算最近位置(从数据库中)的算法.纬度 [英] Algorithm to calculate the nearest location (from the database) based on logitude & latitude

问题描述

我想做的是开发一种算法来计算哪些已知位置最接近所选位置. 假设我在数据库中有7个位置，当用户选择一个位置时，他应该可以选择查看(从数据库中)最近的3个位置.在数据库中，每个位置均按纬度和经度保存.

What i want to do is develop an algorithm to calculate which known locations are closest to the selected location. Let's say i have 7 locations in the database and when the user selects one, he should have the option to see the, let's say, first 3 closest locations (from the database). In the database, each location is saved with latitude and longitude.

关于我该怎么做的任何想法?

Any idea on how i can do that?

示例:说该列表包含100个自行车站点位置.我在5号车站，我想找出列表中其他哪些车站在附近.不是距离，而是它们的位置.

Example: Say the list contains 100 locations of bike stations. I am at station 5, and I want to find out what other stations in the list lies nearby. Not the distance, but their location.

推荐答案

好问题，我们认为在数据库中有以下三个值:

Good question, Let's think we have following three value in DB:

var dataFromDb = [{
    "location": "First location",
    "lat": "1.28210155945393",
    "lng": "103.81722480263163",

}, {
    "location": "Second location",
    "lat": "1.2777380589964",
    "lng": "103.83749709165197",
    "location": "Stop 2"
}, {
    "location": "Third Location",
    "lat": "1.27832046633393",
    "lng": "103.83762574759974",
}];

为两个位置之间的距离创建一个函数:

Create a function for the distance between two places:

function distanceBetweenTwoPlace(firstLat, firstLon, secondLat, secondLon, unit) {
        var firstRadlat = Math.PI * firstLat/180
        var secondRadlat = Math.PI * secondLat/180
        var theta = firstLon-secondLon;
        var radtheta = Math.PI * theta/180
        var distance = Math.sin(firstRadlat) * Math.sin(secondRadlat) + Math.cos(firstRadlat) * Math.cos(secondRadlat) * Math.cos(radtheta);
        if (distance > 1) {
            distance = 1;
        }
        distance = Math.acos(distance)
        distance = distance * 180/Math.PI
        distance = distance * 60 * 1.1515
        if (unit=="K") { distance = distance * 1.609344 }
        if (unit=="N") { distance = distance * 0.8684 }
        return distance
}

定义当前地点:

var currentLat = 1.28210155945393;
var currentLng = 103.81722480263163;

查找1公里内的记录:

for (var i = 0; i < data.length; i++) {
    if (distance(currentLat, currentLng, data[i].lat, data[i].lng, "K") <= 1) {
        console.log(data[i].location);
    }
}

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