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Coordinates

wemap-sdk-js

Class: Coordinates

A Coordinates position using at least latitude (lat) and longitude (lng). Optionnal fields are: altitude (alt) and level.

Basic geo methods are directly accessibles from here: distanceTo, bearingTo, toEcef...

Coordinates are WGS84 and every transformation here uses the ellipsoid, so the local up axis is the ellipsoid normal and the ECEF / ENU geometry reads alt as a height above the ellipsoid.

What alt actually carries is not settled across the SDK, and that predates this class: the position providers put a height above the ground in it (Constants.DEFAULT_ALTITUDE is 1.6m, a phone in a hand), while GeoRef.localToWorld compares it against the absolute floorAltitude / ceilingAltitude of a building level. Both cannot be right. Only differences matter to the geometry here, which is why the ambiguity has never surfaced as a bug, but level detection does depend on the answer.

(Until 2026-08 this class modelled the earth as a sphere of radius R_MAJOR for speed. That cost ~0.35% of anisotropic scale error at mid-latitude and tilted the local vertical by 11.5', i.e. ~33cm of altitude error per 100m of horizontal travel.)

Extended by​

Constructors​

Constructor​

new Coordinates(lat, lng, alt?, level?): Coordinates

Parameters​

lat​

number

lng​

number

alt?​

number | null

level?​

Level_t = null

Returns​

Coordinates

Properties​

autoWrap​

autoWrap: boolean = true

Accessors​

alt​

Get Signature​

get alt(): number | null

alt does not denote the altitude of a point but its height from the "level" field (if defined) or from the ground /!\ This is the providers' convention, not GeoRef's: see the class header.

Returns​

number | null

Set Signature​

set alt(alt): void

Parameters​
alt​

number | null

Returns​

void

ecef​

Get Signature​

get ecef(): Vector3_t

https://gist.github.com/klucar/1536194

Returns​

Vector3_t

ecefToEnuRotation​

Get Signature​

get ecefToEnuRotation(): Quaternion_t

Returns​

Quaternion_t

enuToEcefRotation​

Get Signature​

get enuToEcefRotation(): Quaternion_t

ECEF Transformations (WGS84 ellipsoid)

Returns​

Quaternion_t

heightFromFloor​

Get Signature​

get heightFromFloor(): number | null

Returns​

number | null

Set Signature​

set heightFromFloor(heightFromFloor): void

Parameters​
heightFromFloor​

number | null

Returns​

void

heightFromGround​

Get Signature​

get heightFromGround(): number | null

Returns​

number | null

Set Signature​

set heightFromGround(heightFromGround): void

Parameters​
heightFromGround​

number | null

Returns​

void

lat​

Get Signature​

get lat(): number

Returns​

number

Set Signature​

set lat(lat): void

Parameters​
lat​

number

Returns​

void

latitude​

Get Signature​

get latitude(): number

Returns​

number

Set Signature​

set latitude(_): void

Parameters​
_​

number

Returns​

void

level​

Get Signature​

get level(): Level_t

Returns​

Level_t

Set Signature​

set level(level): void

Parameters​
level​

Level_t

Returns​

void

lng​

Get Signature​

get lng(): number

Returns​

number

Set Signature​

set lng(lng): void

Parameters​
lng​

number

Returns​

void

longitude​

Get Signature​

get longitude(): number

Returns​

number

Set Signature​

set longitude(_): void

Parameters​
_​

number

Returns​

void

Methods​

bearingTo()​

bearingTo(location2): number

Azimuth to another point, in radians, clockwise from north. Taken in the local ENU frame, so it matches the true geodesic azimuth within 0.02" even at 100km.

Parameters​

location2​

Coordinates

Returns​

number

clone()​

clone(): Coordinates

Deep clone coordinates

Returns​

Coordinates

destinationPoint()​

destinationPoint(distance, bearing, elevation?): Coordinates

Parameters​

distance​

number

bearing​

number

elevation?​

number | null

Returns​

Coordinates

Throws​

if elevation is defined and point altitude is not defined

distanceTo()​

distanceTo(location2): number

Returns the ground distance between two points in meters, on the WGS84 ellipsoid. Altitudes are ignored, as many callers compare positions across levels.

The chord between the two ECEF points is exact; converting it back to an arc length on the locally fitting sphere is what costs accuracy, and it costs very little: 3nm at 340m, 3um at 14km, 1.2m at 557km.

The one case where this is worse than the old haversine is a path along the equator, where the arc radius is R_MAJOR but the Gaussian radius is R_MINOR: 264m over 3340km, 9.3km over 10000km, against an exact haversine there. Everywhere else, and at every distance this SDK works at, it is orders of magnitude better.

Parameters​

location2​

Coordinates

Returns​

number

equals()​

equals(other): boolean

Parameters​

other​

Coordinates

Returns​

boolean

equalsWithoutLevel()​

equalsWithoutLevel(other, eps?, epsAlt?): boolean

Parameters​

other​

Coordinates

eps?​

number = EPS_DEG_MM

epsAlt?​

number = EPS_MM

Returns​

boolean

getSegmentProjection()​

getSegmentProjection(p1, p2): Coordinates | null

https://stackoverflow.com/questions/1299567/how-to-calculate-distance-from-a-point-to-a-line-segment-on-a-sphere

Great-circle geometry, so it stays on the sphere: normalizing an ellipsoidal ECEF vector would yield a geocentric direction and shift the projection by tens of meters. The closure test that rejects a point off the segment measures angles between the same unit vectors, for the same reason: mixing in the geodesic distanceTo would compare a great circle with a geodesic and reject valid projections on long segments.

Parameters​

p1​

Coordinates

p2​

Coordinates

Returns​

Coordinates | null

move()​

move(distance, bearing, elevation?): Coordinates

Moves the point by a ground distance (in meters) along a bearing, on the WGS84 ellipsoid. The displacement is built in the local ENU frame as the chord of the arc travelled, then converted back through ECEF. ponytail: micrometer-accurate at working range (7um at 10km), then degrades as distance^3 / radius^2 (7mm at 100km, ~20m at 1200km). Use Karney's geodesics if continental distances ever matter.

Parameters​

distance​

number

bearing​

number

elevation?​

number | null

Returns​

Coordinates

Throws​

if elevation is defined and point altitude is not defined

toCompressedJson()​

toCompressedJson(): CoordinatesCompressedJson

Returns​

CoordinatesCompressedJson

toJson()​

toJson(): CoordinatesJson

Returns​

CoordinatesJson

toString()​

toString(): string

Input / Output

Returns​

string

wrap()​

wrap(): void

Returns​

void

bearingTo()​

static bearingTo(point1, point2): number

Parameters​

point1​

Coordinates

point2​

Coordinates

Returns​

number

distanceBetween()​

static distanceBetween(point1, point2): number

Parameters​

point1​

Coordinates

point2​

Coordinates

Returns​

number

equals()​

static equals(pos1, pos2, eps?, epsAlt?): boolean

Parameters​

pos1​

Coordinates | null

pos2​

Coordinates | null

eps?​

number = EPS_DEG_MM

epsAlt?​

number = EPS_MM

Returns​

boolean

equalsWithoutLevel()​

static equalsWithoutLevel(pos1, pos2, eps?, epsAlt?): boolean

Parameters​

pos1​

Coordinates | null

pos2​

Coordinates | null

eps?​

number = EPS_DEG_MM

epsAlt?​

number = EPS_MM

Returns​

boolean

fromCompressedJson()​

static fromCompressedJson(json): Coordinates

Parameters​

json​

CoordinatesCompressedJson

Returns​

Coordinates

fromECEF()​

static fromECEF(ecef): Coordinates

Parameters​

ecef​

Vector3_t

Returns​

Coordinates

fromJson()​

static fromJson(json): Coordinates

Parameters​

json​

CoordinatesJson

Returns​

Coordinates