我们需要找到一种快速且相当准确的方法,用于谷歌地图上纬度/经度值和多边形的多边形点。经过一些研究 - 发现了一些关于mysql几何扩展的帖子,并且也实现了 -
SELECT id, Contains( PolyFromText( 'POLYGON(".$polygonpath.")' ) , PointFromText( concat( \"POINT(\", latitude, \" \", longitude, \")\" ) ) ) AS
CONTAINS
FROM tbl_points
然而,这并不适用于由大量要点组成的多边形:(
经过一些更多的研究 - 遇到了一种称为Ray-casting算法的标准算法,但是在尝试在MySQL中开发查询之前,想要抓住机会,如果有人已经通过了这个或者遇到了一个有用的链接,如何在MySQL / SQL-server中实现该算法。
所以,简而言之 - 问题是:
任何人都可以提供Ray Cast算法的MySQL / SQL服务器实现吗?
其他细节:
答案 0 :(得分:18)
以下功能(MYSQL版本的Raycasting算法)震撼了我的世界:
CREATE FUNCTION myWithin(p POINT, poly POLYGON) RETURNS INT(1) DETERMINISTIC
BEGIN
DECLARE n INT DEFAULT 0;
DECLARE pX DECIMAL(9,6);
DECLARE pY DECIMAL(9,6);
DECLARE ls LINESTRING;
DECLARE poly1 POINT;
DECLARE poly1X DECIMAL(9,6);
DECLARE poly1Y DECIMAL(9,6);
DECLARE poly2 POINT;
DECLARE poly2X DECIMAL(9,6);
DECLARE poly2Y DECIMAL(9,6);
DECLARE i INT DEFAULT 0;
DECLARE result INT(1) DEFAULT 0;
SET pX = X(p);
SET pY = Y(p);
SET ls = ExteriorRing(poly);
SET poly2 = EndPoint(ls);
SET poly2X = X(poly2);
SET poly2Y = Y(poly2);
SET n = NumPoints(ls);
WHILE i<n DO
SET poly1 = PointN(ls, (i+1));
SET poly1X = X(poly1);
SET poly1Y = Y(poly1);
IF ( ( ( ( poly1X <= pX ) && ( pX < poly2X ) ) || ( ( poly2X <= pX ) && ( pX < poly1X ) ) ) && ( pY > ( poly2Y - poly1Y ) * ( pX - poly1X ) / ( poly2X - poly1X ) + poly1Y ) ) THEN
SET result = !result;
END IF;
SET poly2X = poly1X;
SET poly2Y = poly1Y;
SET i = i + 1;
END WHILE;
RETURN result;
End;
添加
DELIMITER ;;
在函数之前根据需要。 该功能的用法是:
SELECT myWithin(point, polygon) as result;
,其中
point = Point(lat,lng)
polygon = Polygon(lat1 lng1, lat2 lng2, lat3 lng3, .... latn lngn, lat1 lng1)
请注意,多边形应该关闭(通常情况下,如果您正在检索标准kml或googlemap数据,但只是确保它是 - 请注意lat1 lng1设置在最后重复)
我的数据库中没有点和多边形作为几何字段,因此我必须执行以下操作:
Select myWithin(PointFromText( concat( "POINT(", latitude, " ", longitude, ")" ) ),PolyFromText( 'POLYGON((lat1 lng1, ..... latn lngn, lat1 lng1))' ) ) as result
我希望这可以帮助某人。
答案 1 :(得分:5)
我会编写一个自定义UDF,用C或Delphi或您使用的任何高级工具实现光线投射算法:
编写UDF的链接
这是MySQL gis实现的源代码,它查找球体上的点(使用它作为模板来查看如何与MySQL中的空间数据类型进行交互)。
http://www.lenzg.net/archives/220-New-UDF-for-MySQL-5.1-provides-GIS-functions-distance_sphere-and-distance_spheroid.html
从MySQL手册:
http://dev.mysql.com/doc/refman/5.0/en/adding-functions.html
MS Visual C ++的UDF教程
http://rpbouman.blogspot.com/2007/09/creating-mysql-udfs-with-microsoft.html
Delphi中的UDF教程:
Creating a UDF for MySQL in Delphi
有关光线投射算法的源代码
伪代码:http://rosettacode.org/wiki/Ray-casting_algorithm
drDobbs中的文章(请注意文章顶部代码的链接):http://drdobbs.com/cpp/184409586
Delphi(实际上是FreePascal):http://www.cabiatl.com/mricro/raycast/
答案 2 :(得分:2)
以防万一,一个接受MULTIPOLYGON作为输入的MySQL函数:http://forums.mysql.com/read.php?23,286574,286574
DELIMITER $$
CREATE DEFINER=`root`@`localhost` FUNCTION `GISWithin`(pt POINT, mp MULTIPOLYGON) RETURNS int(1)
DETERMINISTIC
BEGIN
DECLARE str, xy TEXT;
DECLARE x, y, p1x, p1y, p2x, p2y, m, xinters DECIMAL(16, 13) DEFAULT 0;
DECLARE counter INT DEFAULT 0;
DECLARE p, pb, pe INT DEFAULT 0;
SELECT MBRWithin(pt, mp) INTO p;
IF p != 1 OR ISNULL(p) THEN
RETURN p;
END IF;
SELECT X(pt), Y(pt), ASTEXT(mp) INTO x, y, str;
SET str = REPLACE(str, 'POLYGON((','');
SET str = REPLACE(str, '))', '');
SET str = CONCAT(str, ',');
SET pb = 1;
SET pe = LOCATE(',', str);
SET xy = SUBSTRING(str, pb, pe - pb);
SET p = INSTR(xy, ' ');
SET p1x = SUBSTRING(xy, 1, p - 1);
SET p1y = SUBSTRING(xy, p + 1);
SET str = CONCAT(str, xy, ',');
WHILE pe > 0 DO
SET xy = SUBSTRING(str, pb, pe - pb);
SET p = INSTR(xy, ' ');
SET p2x = SUBSTRING(xy, 1, p - 1);
SET p2y = SUBSTRING(xy, p + 1);
IF p1y < p2y THEN SET m = p1y; ELSE SET m = p2y; END IF;
IF y > m THEN
IF p1y > p2y THEN SET m = p1y; ELSE SET m = p2y; END IF;
IF y <= m THEN
IF p1x > p2x THEN SET m = p1x; ELSE SET m = p2x; END IF;
IF x <= m THEN
IF p1y != p2y THEN
SET xinters = (y - p1y) * (p2x - p1x) / (p2y - p1y) + p1x;
END IF;
IF p1x = p2x OR x <= xinters THEN
SET counter = counter + 1;
END IF;
END IF;
END IF;
END IF;
SET p1x = p2x;
SET p1y = p2y;
SET pb = pe + 1;
SET pe = LOCATE(',', str, pb);
END WHILE;
RETURN counter % 2;
END
答案 3 :(得分:1)
我想在多边形表上使用上面的mywithin存储过程,所以这里是执行此操作的命令。
使用ogr2ogr将包含多边形的shapefile导入mysql后,如下所示
ogr2ogr -f "mysql" MYSQL:"mydbname,host=localhost,user=root,password=mypassword,port=3306" -nln "mytablename" -a_srs "EPSG:4326" /path/to/shapefile.shp
然后你可以使用MBRwithin预过滤你的桌子和mywithin完成如下
DROP TEMPORARY TABLE IF EXISTS POSSIBLE_POLYS;
CREATE TEMPORARY TABLE POSSIBLE_POLYS(OGR_FID INT,SHAPE POLYGON);
INSERT INTO POSSIBLE_POLYS (OGR_FID, SHAPE) SELECT mytablename.OGR_FID,mytablename.SHAPE FROM mytablename WHERE MBRwithin(@testpoint,mytablename.SHAPE);
DROP TEMPORARY TABLE IF EXISTS DEFINITE_POLY;
CREATE TEMPORARY TABLE DEFINITE_POLY(OGR_FID INT,SHAPE POLYGON);
INSERT INTO DEFINITE_POLY (OGR_FID, SHAPE) SELECT POSSIBLE_POLYS.OGR_FID,POSSIBLE_POLYS.SHAPE FROM POSSIBLE_POLYS WHERE mywithin(@testpoint,POSSIBLE_POLYS.SHAPE);
创建@testpoint,例如,从
创建SET @longitude=120;
SET @latitude=-30;
SET @testpoint =(PointFromText( concat( "POINT(", @longitude, " ", @latitude, ")" ) ));
答案 4 :(得分:1)
现在是 MySQL5.6.1 及以上的空间扩展。请参阅function_st-contains上的Docs。
答案 5 :(得分:1)
回复zarun函数,在多边形内找到lat / long。
我有一个属性表,有lat / long信息。所以我必须得到其lat / long位于polygon lats / longs(我从Google API获得)中的记录。起初我很愚蠢如何使用Zarun功能。所以这是解决方案查询。
SELECT id
FROM properties
WHERE myWithin(
PointFromText(concat( "POINT(", latitude, " ", longitude, ")")),
PolyFromText('POLYGON((37.628134 -77.458334,37.629867 -77.449021,37.62324 -77.445416,37.622424 -77.457819,37.628134 -77.458334))' )
) = 1 limit 0,50;
希望能为像我这样的傻瓜节省时间;)
答案 6 :(得分:1)
这是一个适用于MULTIPOLYGONS的版本(Zarun的改编版仅适用于POLYGONS)。
CREATE FUNCTION GISWithin(p POINT, multipoly MULTIPOLYGON) RETURNS INT(1) DETERMINISTIC
BEGIN
DECLARE n,i,m,x INT DEFAULT 0;
DECLARE pX,pY,poly1X,poly1Y,poly2X,poly2Y DECIMAL(13,10);
DECLARE ls LINESTRING;
DECLARE poly MULTIPOLYGON;
DECLARE poly1,poly2 POINT;
DECLARE result INT(1) DEFAULT 0;
SET pX = X(p);
SET pY = Y(p);
SET m = NumGeometries(multipoly);
WHILE x<m DO
SET poly = GeometryN(multipoly,x);
SET ls = ExteriorRing(poly);
SET poly2 = EndPoint(ls);
SET poly2X = X(poly2);
SET poly2Y = Y(poly2);
SET n = NumPoints(ls);
WHILE i<n DO
SET poly1 = PointN(ls, (i+1));
SET poly1X = X(poly1);
SET poly1Y = Y(poly1);
IF ( ( ( ( poly1X <= pX ) && ( pX < poly2X ) ) || ( ( poly2X <= pX ) && ( pX < poly1X ) ) ) && ( pY > ( poly2Y - poly1Y ) * ( pX - poly1X ) / ( poly2X - poly1X ) + poly1Y ) ) THEN
SET result = !result;
END IF;
SET poly2X = poly1X;
SET poly2Y = poly1Y;
SET i = i + 1;
END WHILE;
SET x = x + 1;
END WHILE;
RETURN result;
End;