一、背景:
如何判断一个指定的经纬度点是否落在一个多边形区域内？
二、实现代码(delphi)
<!--<br /> <br /> Code highlighting produced by Actipro CodeHighlighter (freeware)<br /> http://www.CodeHighlighter.com/<br /> <br /> --> Type
TMyPoint = packed record
X:double;
Y:double;
end ;
{ *------------------------------------------------------------------------------
判断指定的经纬度坐标点是否落在指定的多边形区域内
@paramALon指定点的经度
@paramALat指定点的纬度
@paramAPoints指定多边形区域各个节点坐标
@returnTrue落在范围内False不在范围内
------------------------------------------------------------------------------* }
function IsPtInPoly(ALon,ALat:double;APoints: array of TMyPoint):Boolean;
var
iSum,iCount,iIndex:Integer;
dLon1,dLon2,dLat1,dLat2,dLon:double;
begin
Result: = False;
if (Length(APoints) < 3 ) then
begin
Result: = False;
Exit;
end ;
iSum: = 0 ;
iCount: = Length(APoints);
for iIndex: = 0 to iCount - 1 do
begin
if (iIndex = iCount - 1 ) then
begin
dLon1: = APoints[iIndex].X;
dLat1: = APoints[iIndex].Y;
dLon2: = APoints[ 0 ].X;
dLat2: = APoints[ 0 ].Y;
end
else
begin
dLon1: = APoints[iIndex].X;
dLat1: = APoints[iIndex].Y;
dLon2: = APoints[iIndex + 1 ].X;
dLat2: = APoints[iIndex + 1 ].Y;
end ;
if ((ALat >= dLat1) and (ALat < dLat2)) or ((ALat >= dLat2) and (ALat < dLat1)) then
begin
if (abs(dLat1 - dLat2) > 0 ) then
begin
dLon: = dLon1 - ((dLon1 - dLon2) * (dLat1 - ALat)) / (dLat1 - dLat2);
if (dLon < ALon) then
Inc(iSum);
end ;
end ;
end ;
if (iSum mod 2 <> 0 ) then
Result: = True;
end ;
