<script type="text/javascript">
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/*
* Use Haversine formula to Calculate distance (in km) between two points specified by
* latitude/longitude (in numeric degrees)
*
* from: Haversine formula - R. W. Sinnott, "Virtues of the Haversine",
* Sky and Telescope, vol 68, no 2, 1984
* http://www.census.gov/cgi-bin/geo/gisfaq?Q5.1
*
* example usage from form:
* result.value = LatLon.distHaversine(lat1.value.parseDeg(), long1.value.parseDeg(),
* lat2.value.parseDeg(), long2.value.parseDeg());
* where lat1, long1, lat2, long2, and result are form fields
*/
LatLon.distHaversine = function(lat1, lon1, lat2, lon2) {
var R = 6371; // earth's mean radius in km
var dLat = (lat2-lat1).toRad();
var dLon = (lon2-lon1).toRad();
lat1 = lat1.toRad(), lat2 = lat2.toRad();
var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(lat1) * Math.cos(lat2) *
Math.sin(dLon/2) * Math.sin(dLon/2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c;
return d;
}
/*
* Use Law of Cosines to calculate distance (in km) between two points specified by latitude/longitude
* (in numeric degrees).
*/
LatLon.distCosineLaw = function(lat1, lon1, lat2, lon2) {
var R = 6371; // earth's mean radius in km
var d = Math.acos(Math.sin(lat1.toRad())*Math.sin(lat2.toRad()) +
Math.cos(lat1.toRad())*Math.cos(lat2.toRad())*Math.cos((lon2-lon1).toRad())) * R;
return d;
}
/*
* calculate (initial) bearing between two points
*
* from: Ed Williams' Aviation Formulary, http://williams.best.vwh.net/avform.htm#Crs
*/
LatLon.bearing = function(lat1, lon1, lat2, lon2) {
lat1 = lat1.toRad(); lat2 = lat2.toRad();
var dLon = (lon2-lon1).toRad();
var y = Math.sin(dLon) * Math.cos(lat2);
var x = Math.cos(lat1)*Math.sin(lat2) -
Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon);
return Math.atan2(y, x).toBrng();
}
/*
* calculate midpoint of great circle line between p1 & p2.
* see http://mathforum.org/library/drmath/view/51822.html for derivation
*/
LatLon.midPoint = function(lat1, lon1, lat2, lon2) {
lat1 = lat1.toRad();
lat2 = lat2.toRad();
var dLon = (lon2-lon1).toRad();
var Bx = Math.cos(lat2) * Math.cos(dLon);
var By = Math.cos(lat2) * Math.sin(dLon);
lat3 = Math.atan2(Math.sin(lat1)+Math.sin(lat2),
Math.sqrt((Math.cos(lat1)+Bx)*(Math.cos(lat1)+Bx) + By*By ) );
lon3 = lon1.toRad() + Math.atan2(By, Math.cos(lat1) + Bx);
if (isNaN(lat3) || isNaN(lon3)) return null;
return new LatLon(lat3.toDeg(), lon3.toDeg());
}
/*
* calculate destination point given start point, initial bearing (deg) and distance (km)
* see http://williams.best.vwh.net/avform.htm#LL
*/
LatLon.prototype.destPoint = function(brng, d) {
var R = 6371; // earth's mean radius in km
var lat1 = this.lat.toRad(), lon1 = this.lon.toRad();
brng = brng.toRad();
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));
if (isNaN(lat2) || isNaN(lon2)) return null;
return new LatLon(lat2.toDeg(), lon2.toDeg());
}
/*
* calculate final bearing arriving at destination point given start point, initial bearing and distance
*/
LatLon.prototype.finalBrng = function(brng, d) {
var p1 = this, p2 = p1.destPoint(brng, d);
// get reverse bearing point 2 to point 1
var rev = LatLon.bearing(p2.lat, p2.lon, p1.lat, p1.lon);
// & reverse it by adding 180º
var rev = (rev + 180) % 360;
return rev;
}
/*
* calculate distance, bearing, destination point on rhumb line
* see http://williams.best.vwh.net/avform.htm#Rhumb
*/
LatLon.distRhumb = function(lat1, lon1, lat2, lon2) {
var R = 6371; // earth's mean radius in km
var dLat = (lat2-lat1).toRad(), dLon = Math.abs(lon2-lon1).toRad();
var dPhi = Math.log(Math.tan(lat2.toRad()/2+Math.PI/4)/Math.tan(lat1.toRad()/2+Math.PI/4));
var q = dLat/dPhi;
if (!isFinite(q)) q = Math.cos(lat1.toRad());
// if dLon over 180° take shorter rhumb across 180° meridian:
if (dLon > Math.PI) dLon = 2*Math.PI - dLon;
var d = Math.sqrt(dLat*dLat + q*q*dLon*dLon);
return d * R;
}
LatLon.brngRhumb = function(lat1, lon1, lat2, lon2) {
var dLon = (lon2-lon1).toRad();
var dPhi = Math.log(Math.tan(lat2.toRad()/2+Math.PI/4)/Math.tan(lat1.toRad()/2+Math.PI/4));
if (Math.abs(dLon) > Math.PI) dLon = dLon>0 ? -(2*Math.PI-dLon) : (2*Math.PI+dLon);
return Math.atan2(dLon, dPhi).toBrng();
}
LatLon.prototype.destPointRhumb = function(brng, dist) {
var R = 6371; // earth's mean radius in km
var d = parseFloat(dist)/R; // d = angular distance covered on earth's surface
var lat1 = this.lat.toRad(), lon1 = this.lon.toRad();
brng = brng.toRad();
lat2 = lat1 + d*Math.cos(brng);
var dPhi = Math.log(Math.tan(lat2/2+Math.PI/4)/Math.tan(lat1/2+Math.PI/4));
var q = (lat2-lat1)/dPhi;
if (!isFinite(q)) q = Math.cos(lat1);
var dLon = d*Math.sin(brng)/q;
// check for some daft bugger going past the pole
if (Math.abs(lat2) > Math.PI/2) lat2 = lat2>0 ? Math.PI-lat2 : -Math.PI-lat2;
lon2 = (lon1+dLon+Math.PI)%(2*Math.PI) - Math.PI;
if (isNaN(lat2) || isNaN(lon2)) return null;
return new LatLon(lat2.toDeg(), lon2.toDeg());
}
/*
* construct a LatLon object: arguments in numeric degrees
*
* note all LatLong methods expect & return numeric degrees (for lat/long & for bearings)
*/
function LatLon(lat, lon) {
this.lat = lat;
this.lon = lon;
}
/*
* represent point {lat, lon} in standard representation
*/
LatLon.prototype.toString = function() {
return this.lat.toLat() + ', ' + this.lon.toLon();
}
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
// extend String object with method for parsing degrees or lat/long values to numeric degrees
//
// this is very flexible on formats, allowing signed decimal degrees, or deg-min-sec suffixed by
// compass direction (NSEW). A variety of separators are accepted (eg 3º 37' 09"W) or fixed-width
// format without separators (eg 0033709W). Seconds and minutes may be omitted. (Minimal validation
// is done).
String.prototype.parseDeg = function() {
if (!isNaN(this)) return Number(this); // signed decimal degrees without NSEW
var degLL = this.replace(/^-/,'').replace(/[NSEW]/i,''); // strip off any sign or compass dir'n
var dms = degLL.split(/[^0-9.,]+/); // split out separate d/m/s
for (var i in dms) if (dms[i]=='') dms.splice(i,1); // remove empty elements (see note below)
switch (dms.length) { // convert to decimal degrees...
case 3: // interpret 3-part result as d/m/s
var deg = dms[0]/1 + dms[1]/60 + dms[2]/3600; break;
case 2: // interpret 2-part result as d/m
var deg = dms[0]/1 + dms[1]/60; break;
case 1: // decimal or non-separated dddmmss
if (/[NS]/i.test(this)) degLL = '0' + degLL; // - normalise N/S to 3-digit degrees
var deg = dms[0].slice(0,3)/1 + dms[0].slice(3,5)/60 + dms[0].slice(5)/3600; break;
default: return NaN;
}
if (/^-/.test(this) || /[WS]/i.test(this)) deg = -deg; // take '-', west and south as -ve
return deg;
}
// note: whitespace at start/end will split() into empty elements (except in IE)
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// extend Number object with methods for converting degrees/radians
Number.prototype.toRad = function() { // convert degrees to radians
return this * Math.PI / 180;
}
Number.prototype.toDeg = function() { // convert radians to degrees (signed)
return this * 180 / Math.PI;
}
Number.prototype.toBrng = function() { // convert radians to degrees (as bearing: 0...360)
return (this.toDeg()+360) % 360;
}
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
// extend Number object with methods for presenting bearings & lat/longs
Number.prototype.toDMS = function() { // convert numeric degrees to deg/min/sec
var d = Math.abs(this); // (unsigned result ready for appending compass dir'n)
d += 1/7200; // add ½ second for rounding
var deg = Math.floor(d);
var min = Math.floor((d-deg)*60);
var sec = Math.floor((d-deg-min/60)*3600);
// add leading zeros if required
if (deg<100) deg = '0' + deg; if (deg<10) deg = '0' + deg;
if (min<10) min = '0' + min;
if (sec<10) sec = '0' + sec;
return deg + '\u00B0' + min + '\u2032' + sec + '\u2033';
}
Number.prototype.toLat = function() { // convert numeric degrees to deg/min/sec latitude
return this.toDMS().slice(1) + (this<0 ? 'S' : 'N'); // knock off initial '0' for lat!
}
Number.prototype.toLon = function() { // convert numeric degrees to deg/min/sec longitude
return this.toDMS() + (this>0 ? 'E' : 'W');
}
Number.prototype.toPrecision = function(fig) { // override toPrecision method with one which displays
if (this == 0) return 0; // trailing zeros in place of exponential notation
var scale = Math.ceil(Math.log(this)*Math.LOG10E);
var mult = Math.pow(10, fig-scale);
return Math.round(this*mult)/mult;
}
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</script>
摘之：http://www.movable-type.co.uk/scripts/latlong.html