Question

鉴于我有一张包含机场列表及其相关纬度和长坐标的表格，我如何获取距离另一个坐标100英里范围内的机场列表？我的最终目标是让用户按城市搜索，并找到距离该城市经度和纬度100英里范围内的机场。我所有的数据都不知道从哪里开始。

我的数据在SQL Server中。

Answer 1

create function dbo.F_GREAT_CIRCLE_DISTANCE
(
    @Latitude1  float,
    @Longitude1 float,
    @Latitude2  float,
    @Longitude2 float
)
returns float as
begin
    declare @radius float

    declare @lon1  float
    declare @lon2  float
    declare @lat1  float
    declare @lat2  float

    declare @a float
    declare @distance float

    -- Sets average radius of Earth in Miles
    set @radius = 3956

    -- Convert degrees to radians
    set @lon1 = radians( @Longitude1 )
    set @lon2 = radians( @Longitude2 )
    set @lat1 = radians( @Latitude1 )
    set @lat2 = radians( @Latitude2 )

    set @a = sqrt(square(sin((@lat2-@lat1)/2.0E)) + (cos(@lat1) * cos(@lat2) * square(sin((@lon2-@lon1)/2.0E))) )
    set @distance = @radius * ( 2.0E *asin(case when 1.0E < @a then 1.0E else @a end ))

    return @distance
end

Answer 2

您可以使用System.Device.Location.GeoCoordinate类

GeoCoordinate city = ....;
double distance = .......;
List<GeoCoordinate> airports = .......; //load from db.

var found = airports.Where(c=>c.GetDistanceTo(city) < distance);

修改

对于那些可能对实际工作代码感兴趣的人

var airports1 = Airports.Search(51, 0, 100).ToList(); //~London var airports2 = Airports.Search(40.714623, -74.006605,100).ToList(); //~NY

public class Airports { public class Airport { public string Name; public GeoCoordinate Location; public override string ToString() { return Name; } } static Lazy<List<Airport>> _Airports = new Lazy<List<Airport>>(() => { using (var wc = new WebClient()) { var json = wc.DownloadString("http://www.flightradar24.com/AirportDataService2.php"); var jObj = new JavaScriptSerializer().Deserialize<Dictionary<string,string[]>>(json); return jObj.Values .Select(j => new Airport { Name = (string)j[2], Location = new GeoCoordinate(double.Parse(j[3].ToString(), CultureInfo.InvariantCulture),double.Parse(j[4].ToString(), CultureInfo.InvariantCulture)) }) .ToList(); } }, true); public static IEnumerable<Airport> Search(double lat,double lon, double distInMiles) { var loc = new GeoCoordinate(lat, lon); return _Airports.Value.Where(c => c.Location.GetDistanceTo(loc) < distInMiles * 1609.344); } }

Answer 3

你可以这样做：

 --SELECT Points closer than @radius
select * from #Points p
WHERE power(p.x - @locX, 2) + POWER(p.y - @locY, 2) < POWER(@radius,2)

（这是通过Google搜索SQL + Pyhtagoras找到的http://www.sqlservercentral.com/Forums/Topic1228111-8-1.aspx#bm1229043无耻地撕掉的。

Answer 4

如果您的机场位于0,0点， 30英里半径范围内的所有机场都应在一个圆圈内。要测试点是否在圆内，您需要测试每个方程： sqrt（X * X + Y * Y）＆lt; R，其中X，Y - 每个城市的位置，R = 100英里

Answer 5

以下是'当乌鸦飞过两点之间的距离时的公式：半正矢

formula:     a = sin²(Δφ/2) + cos(φ1).cos(φ2).sin²(Δλ/2)
c = 2.atan2(√a, √(1−a))
d = R.c

其中φ是纬度，λ是经度，R是地球半径（平均半径= 6,371km）请注意，角度需要以弧度为单位才能传递给trig函数！

您可以将此代码翻译成SQL

JavaScript: 
var R = 6371; // km
var dLat = (lat2-lat1).toRad();
var dLon = (lon2-lon1).toRad();
var lat1 = lat1.toRad();
var lat2 = lat2.toRad();

var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
        Math.sin(dLon/2) * Math.sin(dLon/2) * Math.cos(lat1) * Math.cos(lat2); 
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a)); 
var d = R * c;

以下是数学函数的T-SQL页面的链接： http://msdn.microsoft.com/en-us/library/ms188919.aspx

在半径内计算100英里

5 个答案: