Class: LatLonNvectorSpherical

latlon-nvector-spherical~LatLonNvectorSpherical

Latitude/longitude points on an spherical model earth, and methods for calculating distances, bearings, destinations, etc on great circle paths.

Constructor

new LatLonNvectorSpherical(lat, lon)

Creates a LatLon point on spherical model earth.
Parameters:
Name Type Description
lat number Latitude in degrees.
lon number Longitude in degrees.
Source:

Methods

(static) intersection(path1start, path1brngEnd, path2start, path2brngEnd) → {LatLon}

Returns the point of intersection of two paths each defined by point pairs or start point and bearing.
Parameters:
Name Type Description
path1start LatLon Start point of first path.
path1brngEnd LatLon | number End point of first path or initial bearing from first start point.
path2start LatLon Start point of second path.
path2brngEnd LatLon | number End point of second path or initial bearing from second start point.
Source:
Returns:
Destination point (null if no unique intersection defined)
Type
LatLon
Example
var p1 = new LatLon(51.8853, 0.2545), brng1 = 108.55;
  var p2 = new LatLon(49.0034, 2.5735), brng2 =  32.44;
  var pInt = LatLon.intersection(p1, brng1, p2, brng2); // 50.9076°N, 004.5086°E

(static) meanOf(points) → {LatLon}

Returns point representing geographic mean of supplied points.
Parameters:
Name Type Description
points Array.<LatLon> Array of points to be averaged.
Source:
Returns:
Point at the geographic mean of the supplied points.
Type
LatLon

bearingTo(point) → {number}

Returns the (initial) bearing from ‘this’ point to the specified point, in compass degrees.
Parameters:
Name Type Description
point LatLon Latitude/longitude of destination point.
Source:
Returns:
Initial bearing in degrees from North (0°..360°).
Type
number
Example
var p1 = new LatLon(52.205, 0.119);
  var p2 = new LatLon(48.857, 2.351);
  var b1 = p1.bearingTo(p2); // 156.2°

crossTrackDistanceTo(pathStart, pathBrngEnd, radiusopt) → {number}

Returns (signed) distance from ‘this’ point to great circle defined by start-point and end-point/bearing.
Parameters:
Name Type Attributes Default Description
pathStart LatLon Start point of great circle path.
pathBrngEnd LatLon | number End point of great circle path or initial bearing from great circle start point.
radius number <optional>
 6371e3 (Mean) radius of earth (defaults to radius in metres).
Source:
Returns:
Distance to great circle (-ve if to left, +ve if to right of path).
Type
number
Example
var pCurrent = new LatLon(53.2611, -0.7972);

  var p1 = new LatLon(53.3206, -1.7297), brng = 96.0;
  var d = pCurrent.crossTrackDistanceTo(p1, brng); // Number(d.toPrecision(4)): -305.7

  var p1 = new LatLon(53.3206, -1.7297), p2 = new LatLon(53.1887, 0.1334);
  var d = pCurrent.crossTrackDistanceTo(p1, p2);   // Number(d.toPrecision(4)): -307.5

destinationPoint(distance, bearing, radiusopt) → {LatLon}

Returns the destination point from ‘this’ point having travelled the given distance on the given initial bearing (bearing will normally vary before destination is reached).
Parameters:
Name Type Attributes Default Description
distance number Distance travelled, in same units as earth radius (default: metres).
bearing number Initial bearing in degrees from north.
radius number <optional>
 6371e3 (Mean) radius of earth (defaults to radius in metres).
Source:
Returns:
Destination point.
Type
LatLon
Example
var p1 = new LatLon(51.4778, -0.0015);
  var p2 = p1.destinationPoint(7794, 300.7); // 51.5135°N, 000.0983°W

distanceTo(point, radiusopt) → {number}

Returns the distance from ‘this’ point to the specified point.
Parameters:
Name Type Attributes Default Description
point LatLon Latitude/longitude of destination point.
radius number <optional>
 6371e3 (Mean) radius of earth (defaults to radius in metres).
Source:
Returns:
Distance between this point and destination point, in same units as radius.
Type
number
Example
var p1 = new LatLon(52.205, 0.119), p2 = new LatLon(48.857, 2.351);
  var d = p1.distanceTo(p2); // d.toPrecision(4): 404300

enclosedBy(points) → {bool}

Tests whether ‘this’ point is enclosed by the (convex) polygon defined by a set of points.
Parameters:
Name Type Description
points Array.<LatLon> Ordered array of points defining vertices of polygon.
Source:
Throws:
If polygon is not convex.
Type
Error
Returns:
Whether this point is enclosed by region.
Type
bool
Example
var bounds = [ new LatLon(45,1), new LatLon(45,2), new LatLon(46,2), new LatLon(46,1) ];
  var p = new LatLon(45,1, 1.1);
  var inside = p.enclosedBy(bounds); // inside: true;

(private) equals(point) → {bool}

Checks if another point is equal to ‘this’ point.
Parameters:
Name Type Description
point LatLon Point to be compared against this point.
Source:
Returns:
True if points are identical.
Type
bool
Example
var p1 = new LatLon(52.205, 0.119), p2 = new LatLon(52.205, 0.119);
  var equal = p1.equals(p2); // equal: true

(private) greatCircle(bearing) → {Nvector}

Nvector normal to great circle obtained by heading on given bearing from ‘this’ point. Direction of vector is such that initial bearing vector b = c × p.
Parameters:
Name Type Description
bearing number Compass bearing in degrees.
Source:
Returns:
Normalised vector representing great circle.
Type
Nvector
Example
var p1 = new LatLon(53.3206, -1.7297);
  var gc = p1.greatCircle(96.0); // [-0.794,0.129,0.594]

midpointTo(point) → {LatLon}

Returns the midpoint between ‘this’ point and specified point.
Parameters:
Name Type Description
point LatLon Latitude/longitude of destination point.
Source:
Returns:
Midpoint between this point and destination point.
Type
LatLon
Example
var p1 = new LatLon(52.205, 0.119);
  var p2 = new LatLon(48.857, 2.351);
  var pMid = p1.midpointTo(p2); // 50.5363°N, 001.2746°E

nearestPointOnSegment(point1, point2) → {number}

Returns closest point on great circle segment between point1 & point2 to ‘this’ point. If this point is ‘within’ the extent of the segment, the point is on the segment between point1 & point2; otherwise, it is the closer of the endpoints defining the segment.
Parameters:
Name Type Description
point1 LatLon Start point of great circle segment.
point2 LatLon End point of great circle segment.
Source:
Returns:
Nearest point on segment.
Type
number
Example
var p1 = new LatLon(51.0, 1.0), p2 = new LatLon(51.0, 2.0);

  var p0 = new LatLon(51.0, 1.9);
  var p = p0.nearestPointOnSegment(p1, p2); // 51.0004°N, 001.9000°E
  var d = p.distanceTo(p);                  // 42.71

  var p0 = new LatLon(51.0, 2.1);
  var p = p0.nearestPointOnSegment(p1, p2); // 51.0000°N, 002.0000°E

(private) toNvector() → {Nvector}

Converts ‘this’ lat/lon point to n-vector (normal to earth's surface).
Source:
Returns:
Normalised n-vector representing lat/lon point.
Type
Nvector
Example
var p = new LatLon(45, 45);
  var v = p.toNvector(); // [0.5000,0.5000,0.7071]

toString(formatopt, dpopt) → {string}

Returns a string representation of ‘this’ point, formatted as degrees, degrees+minutes, or degrees+minutes+seconds.
Parameters:
Name Type Attributes Default Description
format string <optional>
 dms Format point as 'd', 'dm', 'dms'.
dp number <optional>
 0|2|4 Number of decimal places to use: default 0 for dms, 2 for dm, 4 for d.
Source:
Returns:
Comma-separated formatted latitude/longitude.
Type
string