Sql server 从GPS坐标组获取最大距离
所以我有一个包含多行GPS坐标的数据库。我知道如何计算从给定lat/lng到数据库中任意一行的距离,但我想做的基本上是查看一组行的坐标,并得到相距最远的两行。如果我能在SQL中做到这一点,我会很高兴,但如果我必须在我的应用程序代码中做到这一点,这将非常有用。下面是我计算两点之间距离的步骤:Sql server 从GPS坐标组获取最大距离,sql-server,coldfusion,gps,Sql Server,Coldfusion,Gps,所以我有一个包含多行GPS坐标的数据库。我知道如何计算从给定lat/lng到数据库中任意一行的距离,但我想做的基本上是查看一组行的坐标,并得到相距最远的两行。如果我能在SQL中做到这一点,我会很高兴,但如果我必须在我的应用程序代码中做到这一点,这将非常有用。下面是我计算两点之间距离的步骤: ROUND(( 3960 * acos( cos( radians( :lat ) ) * cos( radians( p.latitude ) ) * cos( radians( p.longitude
ROUND(( 3960 * acos( cos( radians( :lat ) ) *
cos( radians( p.latitude ) ) * cos( radians( p.longitude ) - radians( :lng ) ) +
sin( radians( :lat ) ) * sin( radians( p.latitude ) ) ) ),1) AS distance
我们试图做的是,查看特定用户的GPS数据,确保它们不会在全国范围内疯狂移动。用户的所有坐标最多应在几英里以内。如果坐标遍布全国,则表明我们的系统中存在恶意活动。因此,我希望能够快速浏览SPCIC用户的数据,并了解他们的最大距离
我考虑在lat和lng上分别运行Max/Min,并设置一个可接受的内部阈值。也许这更容易,但如果我在第一部分中所问的是可能的,那将是最好的。如果您有SQL Server 2008或更高版本,那么您可以使用地理位置来计算距离,例如:
DECLARE @lat1 DECIMAL(19,6) = 44.968046;
DECLARE @lon1 DECIMAL(19,6) = -94.420307;
DECLARE @lat2 DECIMAL(19,6) = 44.33328;
DECLARE @lon2 DECIMAL(19,6) = -89.132008;
SELECT GEOGRAPHY::Point(@lat1, @lon1, 4326).STDistance(GEOGRAPHY::Point(@lat2, @lon2, 4326));
这使得这个问题变得非常简单
对于用户的一组lat/long,您需要计算每组之间的距离,然后返回最大距离。综上所述,您可能可以这样做:
DECLARE @UserGPS TABLE (
UserId INT, --the user
GPSId INT, --the incrementing unique id associated with this GPS reading (could link to a table with more details, e.g. time, date)
Lat DECIMAL(19,6), --lattitude
Lon DECIMAL(19,6)); --longitude
INSERT INTO @UserGPS SELECT 1, 1, 44.968046, -94.420307; --User #1 goes on a very long journey
INSERT INTO @UserGPS SELECT 1, 2, 44.33328, -89.132008;
INSERT INTO @UserGPS SELECT 1, 3, 34.12345, -92.21369;
INSERT INTO @UserGPS SELECT 1, 4, 44.978046, -94.430307;
INSERT INTO @UserGPS SELECT 2, 1, 44.968046, -94.420307; --User #2 doesn't get far
INSERT INTO @UserGPS SELECT 2, 2, 44.978046, -94.430307;
--Make a working table to store the distances between each set of co-ordinates
--This isn't strictly necessary; we could change this into a common-table expression
DECLARE @WorkTable TABLE (
UserId INT, --the user
GPSIdFrom INT, --the id of the first set of co-ordinates
GPSIdTo INT, --the id of the second set of co-ordinates being compared
Distance NUMERIC(19,6)); --the distance
--Get the distance between each and every combination of co-ordinates for each user
INSERT INTO
@WorkTable
SELECT
c1.UserId,
c1.GPSId,
c2.GPSId,
GEOGRAPHY::Point(c1.Lat, c1.Lon, 4326).STDistance(GEOGRAPHY::Point(c2.Lat, c2.Lon, 4326))
FROM
@UserGPS c1
INNER JOIN @UserGPS c2 ON c2.UserId = c1.UserId AND c2.GPSId > c1.GPSId;
--Note this is a self-join, but single-tailed. So we compare each set of co-ordinates to each other set of co-ordinates for a user
--This is handled by the "c2.GPSID > c1.GPSId" in the JOIN clause
--As an example, say we have three sets of co-ordinates for a user
--We would compare set #1 to set #2
--We would compare set #1 to set #3
--We would compare set #2 to set #3
--We wouldn't compare set #3 to anything (as we already did this)
--Determine the maximum distance between all the GPS co-ordinates per user
WITH MaxDistance AS (
SELECT
UserId,
MAX(Distance) AS Distance
FROM
@WorkTable
GROUP BY
UserId)
--Report the results
SELECT
w.UserId,
g1.GPSId,
g1.Lat,
g1.Lon,
g2.GPSId,
g2.Lat,
g2.Lon,
md.Distance AS MaxDistance
FROM
MaxDistance md
INNER JOIN @WorkTable w ON w.UserId = md.UserId AND w.Distance = md.Distance
INNER JOIN @UserGPS g1 ON g1.UserId = md.UserId AND g1.GPSId = w.GPSIdFrom
INNER JOIN @UserGPS g2 ON g2.UserId = md.UserId AND g2.GPSId = w.GPSIdTo;
结果如下:
UserId GPSId Lat Lon GPSId Lat Lon MaxDistance
1 3 34.123450 -92.213690 4 44.978046 -94.430307 1219979.460185
2 1 44.968046 -94.420307 2 44.978046 -94.430307 1362.820895
现在我对你持有的数据做了很多假设,因为在你的问题中没有关于这个细节的信息。您可能需要在某种程度上对其进行调整?因此它看起来只比较了两行。如果我有50行,每行都有不同的lat/lng值呢。是否有一种方法可以将它们相互比较,并返回两行之间的最大距离。不,这将为用户比较所有行,它使用单尾方法,因此如果有三行,它将比较第1行、第2行和第3行,然后从第2排到第3排,然后返回距离最高的比赛。在我的示例中,第一个用户有四组坐标,它计算的最大距离为值3和值4之间。我希望我能理解它是如何做到的。我在我的答案中添加了一些注释,试图解释它是如何工作的。感谢您的帮助。现在就开始测试。