多边形中的孔 [英] Holes in a Polygon
问题描述
首先给那些想对我的低接受率评论的人... im new，让我休息一下。
我添加了这个多边形代码本网站：
http://www.geocodezip.com/v3_polygon_example_donut.html
虽然有一个问题，但半径不准确。所以如果我测量两个城市之间的距离，那么画出这个圆圈，它就会离开，并且圆圈越大越差。
有什么想法吗？
< script type =text / javascript>
函数drawCircle（point，radius，dir）{
var d2r = Math.PI / 180; //度数为弧度
var r2d = 180 / Math.PI; //弧度度数
var earthsradius = 3959; // 3959是SM
var points = 1000中地球的半径;
//找到lat / lon中的raidus
var rlat =（radius / earthsradius）* r2d;
var rlng = rlat / Math.cos（point.lat（）* d2r）;
var extp = new Array（）;
if（dir == 1）{var start = 0; var end = points + 1} //另外一个确保我们连接
else {var start = points + 1; var end = 0}
for（var i = start;（dir == 1？i< end：i> end）; i = i + dir）
{
var theta = Math。 PI *（i /（points / 2））;
ey = point.lng（）+（rlng * Math.cos（theta））; //中心a +半径x * cos（theta）
ex = point.lat（）+（rlat * Math.sin（theta））; // center b + radius y * sin（theta）
extp.push（new google.maps.LatLng（ex，ey））;
bounds.extend（extp [extp.length-1]）;
}
// alert（extp.length）;
返回extp;
}
var map = null;
var bounds = null;
函数initialize（）{
var myOptions = {
zoom：10，
center：new google.maps.LatLng（29.10860062，-95.46209717），
mapTypeControl：true，
mapTypeControlOptions：{style：google.maps.MapTypeControlStyle.DROPDOWN_MENU}，
navigationControl：true，
mapTypeId：google.maps.MapTypeId.TERRAIN
}
map = new google.maps.Map（document.getElementById（map_canvas），
myOptions）;
bounds = new google.maps.LatLngBounds（）;
var donut = new google.maps.Polygon（{
paths：[triangleCoords = [
new google.maps.LatLng（-87，120），
new google.maps.LatLng（-87，-87），
new google.maps.LatLng（-87，0）]，
drawCircle（new google.maps.LatLng（29.10860062，-95.46209717） ，2000，-1）]，;
strokeColor：＃000000，
strokeOpacity：0.6，
strokeWeight：2，
fillColor：＃999999 ，
fillOpacity：0.6
））;
donut.setMap（map）;
map.fitBounds（bounds）;
< / script>
圆形绘图程序可以通过使用计算中的轴承点计算找到http://www.movable-type.co.uk/scripts/latlong.html#destPoint
θ是方位（以弧度表示，从北方顺时针）;
d / R是角距离（以弧度为单位），其中d是行驶的距离，R是地球的半径b
$ b
Math2 ）;
var lon2 = lon1 + Math.atan2（Math.sin（brng）* Math.sin（d / R）* Math.cos（lat1），
Math.cos（d / R）-Math .sin（LAT1）* Math.sin（LAT2））;
将所有内容转换为弧度并确保d和R都以相同的单位表示，一个像这样的圆圈绘制例程
$ p $
函数drawCircle（point，radius，dir，addtoBounds）{
var d2r = Math.PI / 180; //度数为弧度
var r2d = 180 / Math.PI; //弧度度数
var earthsradius = 6371000; // 3959是SM
var points = 1000中地球的半径;
//找到lat / lon中的raidus
var rlat =（radius / earthsradius）* r2d;
var rlng = rlat / Math.cos（point.lat（）* d2r）;
var extp = new Array（）;
if（dir == 1）{var start = 0; var end = points + 1} //另外一个确保我们连接
else {var start = points + 1; var end = 0}
for（var i = start;（dir == 1？i< end：i> end）; i = i + dir）
{
var theta = Math。 PI *（i /（points / 2））;
var lat1 = point.lat（）* d2r;
var lon1 = point.lng（）* d2r;
var d = radius;
var R = earthsradius;
var ex = Math.asin（Math.sin（lat1）* Math.cos（d / R）+
Math.cos（lat1）* Math.sin（d / R） * Math.cos（theta））;
var ey = lon1 + Math.atan2（Math.sin（theta）* Math.sin（d / R）* Math.cos（lat1），
Math.cos（d / R）-Math .sin（LAT1）* Math.sin（EX））;
extp.push（new google.maps.LatLng（ex * r2d，ey * r2d））;
if（addtoBounds）bounds.extend（extp [extp.length-1]）;
}
// alert（extp.length）;
返回extp;
}
我在 http://www.acleach.me.uk/gmaps/v3/mapsearch.htm 中心位于CYQX和EINN还有另一个标记和一圈1715NM的半径（表示为3176180米）。其他圈子以500,1000,1500,2000和2500NM的半径被添加。
我还在这两点之间增加了测地线。这与预期的直角相交，这是检查圆圈计算的准确性。
First off to those that want to make a comment about my low acceptance rating...im new, give me a break.
I added this polygon code from this website: http://www.geocodezip.com/v3_polygon_example_donut.html
There is an issue though, the radius is not accurate. So if I measure the distance between 2 cities, then draw this circle, it is way off, and gets worse the larger the circle.
Any ideas?
<script type="text/javascript">
function drawCircle(point, radius, dir) {
var d2r = Math.PI / 180; // degrees to radians
var r2d = 180 / Math.PI; // radians to degrees
var earthsradius = 3959; // 3959 is the radius of the earth in SM
var points = 1000;
// find the raidus in lat/lon
var rlat = (radius / earthsradius) * r2d;
var rlng = rlat / Math.cos(point.lat() * d2r);
var extp = new Array();
if (dir==1) {var start=0;var end=points+1} // one extra here makes sure we connect the
else {var start=points+1;var end=0}
for (var i=start; (dir==1 ? i < end : i > end); i=i+dir)
{
var theta = Math.PI * (i / (points/2));
ey = point.lng() + (rlng * Math.cos(theta)); // center a + radius x * cos(theta)
ex = point.lat() + (rlat * Math.sin(theta)); // center b + radius y * sin(theta)
extp.push(new google.maps.LatLng(ex, ey));
bounds.extend(extp[extp.length-1]);
}
// alert(extp.length);
return extp;
}
var map = null;
var bounds = null;
function initialize() {
var myOptions = {
zoom: 10,
center: new google.maps.LatLng(29.10860062, -95.46209717),
mapTypeControl: true,
mapTypeControlOptions: {style: google.maps.MapTypeControlStyle.DROPDOWN_MENU},
navigationControl: true,
mapTypeId: google.maps.MapTypeId.TERRAIN
}
map = new google.maps.Map(document.getElementById("map_canvas"),
myOptions);
bounds = new google.maps.LatLngBounds();
var donut = new google.maps.Polygon({
paths: [triangleCoords = [
new google.maps.LatLng(-87, 120),
new google.maps.LatLng(-87, -87),
new google.maps.LatLng(-87, 0)],
drawCircle(new google.maps.LatLng(29.10860062, -95.46209717), 2000, -1)],";
strokeColor: "#000000",
strokeOpacity: 0.6,
strokeWeight: 2,
fillColor: "#999999",
fillOpacity: 0.6
});
donut.setMap(map);
map.fitBounds(bounds);
</script>
A better circle-drawing routine may be found by using the "point from bearing" calculations at http://www.movable-type.co.uk/scripts/latlong.html#destPoint
θ is the bearing (in radians, clockwise from north); d/R is the angular distance (in radians), where d is the distance travelled and R is the earth’s radius
var lat2 = Math.asin( Math.sin(lat1)*Math.cos(d/R) +
Math.cos(lat1)*Math.sin(d/R)*Math.cos(brng) );
var lon2 = lon1 + Math.atan2(Math.sin(brng)*Math.sin(d/R)*Math.cos(lat1),
Math.cos(d/R)-Math.sin(lat1)*Math.sin(lat2));
Converting everything to radians and making sure that d and R are both expressed in the same units, we get a circle-drawing routine like this
function drawCircle(point, radius, dir, addtoBounds) {
var d2r = Math.PI / 180; // degrees to radians
var r2d = 180 / Math.PI; // radians to degrees
var earthsradius = 6371000; // 3959 is the radius of the earth in SM
var points = 1000;
// find the raidus in lat/lon
var rlat = (radius / earthsradius) * r2d;
var rlng = rlat / Math.cos(point.lat() * d2r);
var extp = new Array();
if (dir==1) {var start=0;var end=points+1} // one extra here makes sure we connect the
else {var start=points+1;var end=0}
for (var i=start; (dir==1 ? i < end : i > end); i=i+dir)
{
var theta = Math.PI * (i / (points/2));
var lat1=point.lat()*d2r;
var lon1=point.lng()*d2r;
var d=radius;
var R=earthsradius;
var ex = Math.asin( Math.sin(lat1)*Math.cos(d/R) +
Math.cos(lat1)*Math.sin(d/R)*Math.cos(theta) );
var ey = lon1 + Math.atan2(Math.sin(theta)*Math.sin(d/R)*Math.cos(lat1),
Math.cos(d/R)-Math.sin(lat1)*Math.sin(ex));
extp.push(new google.maps.LatLng(ex*r2d, ey*r2d));
if (addtoBounds) bounds.extend(extp[extp.length-1]);
}
// alert(extp.length);
return extp;
}
I have an example at http://www.acleach.me.uk/gmaps/v3/mapsearch.htm where the centre is at CYQX and there's another marker at EINN and a circle of 1715NM radius (expressed as 3176180m). Other circles have been added at radii of 500, 1000, 1500, 2000 and 2500NM.
I've also added a geodesic line between the two points. This crosses the circles at right-angles as expected, which is a check on the accuracy of the circle calculation.
这篇关于多边形中的孔的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
