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GeoLocation.js
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GeoLocation.js
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/**
* <p>Represents a point on the surface of a sphere. (The Earth is almost
* spherical.)</p>
*
* <p>To create an instance, call one of the static methods fromDegrees() or
* fromRadians().</p>
*
* <p>This code was originally published at
* <a href="http://JanMatuschek.de/LatitudeLongitudeBoundingCoordinates#Java">
* http://JanMatuschek.de/LatitudeLongitudeBoundingCoordinates#Java</a>.</p>
*
* @author Jan Philip Matuschek
* @version 22 September 2010
*/
function GeoLocation () {
this._MIN_LAT = this._toRad(-90)
this._MAX_LAT = this._toRad(90)
this._MIN_LON = this._toRad(-180)
this._MAX_LON = this._toRad(180)
}
GeoLocation.prototype.getLatitudeInDegrees = function () {
return this._degLat
}
GeoLocation.prototype.getLongitudeInDegrees = function () {
return this._degLon
}
GeoLocation.prototype.getLatitudeInRadians = function () {
return this._radLat
}
GeoLocation.prototype.getLongitudeInRadians = function () {
return this._radLon
}
GeoLocation.prototype.toString = function () {
return '(' + this._degLat + '\u00B0, ' + this._degLon + '\u00B0) = (' +
this._radLat + ' rad, ' + this._radLon + ' rad)'
}
/**
* Computes the great circle distance between this GeoLocation instance
* and the location argument.
* @param {object} location second location
* @param {double} radius the radius of the sphere, e.g. the average radius for a
* spherical approximation of the figure of the Earth is approximately
* 6371.01 kilometers.
* @return the distance, measured in the same unit as the radius
* argument.
*/
GeoLocation.prototype.distanceTo = function (location, radius) {
return Math.acos(
Math.sin(this._radLat) * Math.sin(location.getLatitudeInRadians()) +
Math.cos(this._radLat) * Math.cos(location.getLatitudeInRadians()) *
Math.cos(this._radLon - location.getLongitudeInRadians())
) * radius
}
/**
* <p>Computes the bounding coordinates of all points on the surface
* of a sphere that have a great circle distance to the point represented
* by this GeoLocation instance that is less or equal to the distance
* argument.</p>
* <p>For more information about the formulae used in this method visit
* <a href="http://JanMatuschek.de/LatitudeLongitudeBoundingCoordinates">
* http://JanMatuschek.de/LatitudeLongitudeBoundingCoordinates</a>.</p>
* @param {double} distance the distance from the point represented by this
* GeoLocation instance. Must me measured in the same unit as the radius
* argument.
* @param {double} radius the radius of the sphere, e.g. the average radius for a
* spherical approximation of the figure of the Earth is approximately
* 6371.01 kilometers.
* @return {array} an array of two GeoLocation objects such that:<ul>
* <li>The latitude of any point within the specified distance is greater
* or equal to the latitude of the first array element and smaller or
* equal to the latitude of the second array element.</li>
* <li>If the longitude of the first array element is smaller or equal to
* the longitude of the second element, then
* the longitude of any point within the specified distance is greater
* or equal to the longitude of the first array element and smaller or
* equal to the longitude of the second array element.</li>
* <li>If the longitude of the first array element is greater than the
* longitude of the second element (this is the case if the 180th
* meridian is within the distance), then
* the longitude of any point within the specified distance is greater
* or equal to the longitude of the first array element
* <strong>or</strong> smaller or equal to the longitude of the second
* array element.</li>
* </ul>
*/
GeoLocation.prototype.boundingCoordinates = function (distance, radius) {
if (radius < 0 || isNaN(radius)) throw new Error('Wrong radius')
if (distance < 0 || isNaN(distance)) throw new Error('Wrong distance')
var radDis = distance / radius
var minLat = this._radLat - radDis
var maxLat = this._radLat + radDis
var minLon
var maxLon
var boundingBox = []
if (minLat > this._MIN_LAT && maxLat < this._MAX_LAT) {
var deltaLon = Math.asin(Math.sin(radDis) / Math.cos(this._radLat))
minLon = this._radLon - deltaLon
if (minLon < this._MIN_LON) minLon += 2 * Math.PI
maxLon = this._radLon + deltaLon
if (maxLon > this._MAX_LON) maxLon -= 2 * Math.PI
} else {
// a pole is within the distance
minLat = Math.max(minLat, this._MIN_LAT)
maxLat = Math.min(maxLat, this._MAX_LAT)
minLon = this._MIN_LON
maxLon = this._MAX_LON
}
boundingBox.push(fromRadians(minLat, minLon))
boundingBox.push(fromRadians(maxLat, maxLon))
return boundingBox
}
GeoLocation.prototype._checkBounds = function () {
if (this._radLat < this._MIN_LAT || this._radLat > this._MAX_LAT ||
this._radLon < this._MIN_LON || this._radLon > this._MAX_LON) {
throw new Error('Wrong latitude or longitude')
};
}
GeoLocation.prototype._toRad = function (degrees) {
return degrees * Math.PI / 180
}
GeoLocation.prototype._toDregrees = function (radians) {
return radians * 180 / Math.PI
}
/**
*
* @param {double} latitude in degrees
* @param {double} longitude in degrees
* @return {Object} GeoLocation
*/
function fromDegrees (latitude, longitude) {
var geoLoc = new GeoLocation()
geoLoc._radLat = geoLoc._toRad(latitude)
geoLoc._radLon = geoLoc._toRad(longitude)
geoLoc._degLat = latitude
geoLoc._degLon = longitude
geoLoc._checkBounds()
return geoLoc
}
/**
*
* @param {double} latitude in radians
* @param {double} longitude in radians
* @return {Object} GeoLocation
*/
function fromRadians (latitude, longitude) {
var geoLoc = new GeoLocation()
geoLoc._radLat = latitude
geoLoc._radLon = longitude
geoLoc._degLat = geoLoc._toDregrees(latitude)
geoLoc._degLon = geoLoc._toDregrees(longitude)
geoLoc._checkBounds()
return geoLoc
}
exports.fromDegrees = fromDegrees
exports.fromRadians = fromRadians