itowns-desplandis-geographic v2.44.2

iTowns Geographic

The geographic package provides utilities for handling coordinates, ellipsoids, extents and rotations across different coordinate systems.

• Coordinates : A Coordinates object (geodetic datum), defined by a crs and three values.
• Extent : Extent is geographical bounding rectangle defined by 4 limits: west, east, south and north.
• Crs : This module provides basic methods to manipulate a CRS (as a string). Visiting epsg.io to more coordinate system worldwide. Use Proj4js definition in epsg.io.
• OrientationUtils : it provides methods to compute the quaternion that models a rotation defined with various conventions, including between different CRS.
• Ellipsoid : In geodesy, a reference ellipsoid is a mathematically defined surface that approximates the geoid.

Install

npm install --save @itowns/geographic

Getting started

import { Coordinates, Extent, CRS } from '@itowns/geographic';

const coordinates = new Coordinates('EPSG:4326', 88.002445, 50.336522, 120.32201);
const extent = new Extent('EPSG:4326', 88.002445, 50.336522, 22.021, 50.302548);

// change projection system to pseudo mercator

coordinates.as('EPSG:3857');
extent.as('EPSG:3857');

// change projection system to EPSG:2154

// defs EPSG:2154 crs (visiting epsg.io to get new definition and export to Proj4js)
CRS.defs('EPSG:2154','+proj=lcc +lat_0=46.5 +lon_0=3 +lat_1=49 +lat_2=44 +x_0=700000 +y_0=6600000 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs +type=crs');

coordinates.as('EPSG:2154');

OrientationUtils example

In geodesy, attitude refers to the orientation of a geodetic instrument or platform in three-dimensional space. It is defined by the angles that describe how an instrument or a vehicle (like a satellite or aircraft) is positioned relative to a reference coordinate system, typically the Earth's surface or a local tangent plane.

// Compute the rotation around the point of origin from a frame aligned with Lambert93 axes (epsg:2154),
// to the geocentric frame (epsg:4978)
quat_crs2crs = OrientationUtils.quaternionFromCRSToCRS("EPSG:2154", "EPSG:4978")(origin);
// Compute the rotation of a sensor platform defined by its attitude
quat_attitude = OrientationUtils.quaternionFromAttitude(attitude);
// Compute the rotation from the sensor platform frame to the geocentric frame
quat = quat_crs2crs.multiply(quat_attitude);

Visit the iTowns documentation for more information.