Class: LatLonEllipsoidal_Datum

latlon-ellipsoidal-datum~LatLonEllipsoidal_Datum(lat, lon, heightopt, datum)

Latitude/longitude points on an ellipsoidal model earth, with ellipsoid parameters and methods for converting between datums and to geocentric (ECEF) cartesian coordinates.

Constructor

new LatLonEllipsoidal_Datum(lat, lon, heightopt, datum)

Creates a geodetic latitude/longitude point on an ellipsoidal model earth using given datum.
Parameters:
Name Type Attributes Default Description
lat number Latitude (in degrees).
lon number Longitude (in degrees).
height number <optional>
 0 Height above ellipsoid in metres.
datum LatLon.datums Datum this point is defined within.
Source:
Example
import LatLon from '/js/geodesy/latlon-ellipsoidal-datum.js';
  const p = new LatLon(53.3444, -6.2577, 17, LatLon.datums.Irl1975);

Extends

  • LatLonEllipsoidal

Members

(static) datums

Datums; with associated ellipsoid, and Helmert transform parameters to convert from WGS-84 into given datum. Note that precision of various datums will vary, and WGS-84 (original) is not defined to be accurate to better than ±1 metre. No transformation should be assumed to be accurate to better than a metre, for many datums somewhat less. This is a small sample of commoner datums from a large set of historical datums. I will add new datums on request.
Source:
Example
const a = LatLon.datums.OSGB36.ellipsoid.a;                    // 6377563.396
  const tx = LatLon.datums.OSGB36.transform;                     // [ tx, ty, tz, s, rx, ry, rz ]
  const availableDatums = Object.keys(LatLon.datums).join(', '); // ED50, Irl1975, NAD27, ...

(static) ellipsoids

Ellipsoids with their parameters; semi-major axis (a), semi-minor axis (b), and flattening (f). Flattening f = (a−b)/a; at least one of these parameters is derived from defining constants.
Source:
Example
const a = LatLon.ellipsoids.Airy1830.a; // 6377563.396

datum

Datum this point is defined within.
Source:

Methods

(static) parse(lat|latlon, lonopt, heightopt, datumopt) → {LatLon}

Parses a latitude/longitude point from a variety of formats. Latitude & longitude (in degrees) can be supplied as two separate parameters, as a single comma-separated lat/lon string, or as a single object with { lat, lon } or GeoJSON properties. The latitude/longitude values may be numeric or strings; they may be signed decimal or deg-min-sec (hexagesimal) suffixed by compass direction (NSEW); a variety of separators are accepted. Examples -3.62, '3 37 12W', '3°37′12″W'. Thousands/decimal separators must be comma/dot; use Dms.fromLocale to convert locale-specific thousands/decimal separators.
Parameters:
Name Type Attributes Default Description
lat|latlon number | string | Object Geodetic Latitude (in degrees) or comma-separated lat/lon or lat/lon object.
lon number <optional>
 Longitude in degrees.
height number <optional>
 0 Height above ellipsoid in metres.
datum LatLon.datums <optional>
 WGS84 Datum this point is defined within.
Source:
Throws:
Unrecognised datum.
Type
TypeError
Returns:
Latitude/longitude point on ellipsoidal model earth using given datum.
Type
LatLon
Example
const p = LatLon.parse('51.47736, 0.0000', 0, LatLon.datums.OSGB36);

convertDatum(toDatum) → {LatLon}

Converts ‘this’ lat/lon coordinate to new coordinate system.
Parameters:
Name Type Description
toDatum LatLon.datums Datum this coordinate is to be converted to.
Source:
Throws:
Unrecognised datum.
Type
TypeError
Returns:
This point converted to new datum.
Type
LatLon
Example
const pWGS84 = new LatLon(51.47788, -0.00147, 0, LatLon.datums.WGS84);
  const pOSGB = pWGS84.convertDatum(LatLon.datums.OSGB36); // 51.4773°N, 000.0001°E

toCartesian() → {Cartesian}

Converts ‘this’ point from (geodetic) latitude/longitude coordinates to (geocentric) cartesian (x/y/z) coordinates, based on the same datum. Shadow of LatLonEllipsoidal.toCartesian(), returning Cartesian augmented with LatLonEllipsoidal_Datum methods/properties.
Source:
Returns:
Cartesian point equivalent to lat/lon point, with x, y, z in metres from earth centre, augmented with reference frame conversion methods and properties.
Type
Cartesian