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Chikyu Earth地球

A line-drawn globe of the world's countries that turns at the Earth's own rate, with an optional realistic Earth from space and markers for any place.

Chikyu is the Japanese word 地球 for the Earth. About the name

Contents

Reference · Passes: when a satellite crosses the sky over a place

groundTrackfunction

The places straight under a satellite from one moment to another: its ground track. Use a pass's start.ms and end.ms for the track of one pass, to draw on a globe.

Import it

import { groundTrack } from "@johnmorrisdotca/chikyu-earth/passes";

Definition

function groundTrack(set: ElementSet, fromMs: number, toMs: number, stepSeconds?: number): GroundPoint[]

Parameters

NameTypeDescription
setElementSet

The satellite's elements.

fromMsnumber

The first moment, milliseconds since the Unix epoch.

toMsnumber

The last moment.

stepSeconds (optional)number

Seconds between points (10 by default).

Returns

GroundPoint[]

The points, in time order; a moment SGP4 gives no place for is left out.

Examples

import { groundTrack } from "@johnmorrisdotca/chikyu-earth/passes";

const iss = {
  OBJECT_NAME: "ISS (ZARYA)",
  EPOCH: "2026-11-02T10:25:21.580320",
  MEAN_MOTION: 15.49150046,
  ECCENTRICITY: 0.0007139,
  INCLINATION: 51.6332,
  RA_OF_ASC_NODE: 335.9757,
  ARG_OF_PERICENTER: 339.3739,
  MEAN_ANOMALY: 20.6961,
  NORAD_CAT_ID: 25544,
  BSTAR: 0.00012,
  MEAN_MOTION_DOT: 0.0001,
  MEAN_MOTION_DDOT: 0,
};
const noon = Date.UTC(2026, 10, 3, 12);
const track = groundTrack(iss, noon, noon + 10 * 60_000);
console.log(track.length, Math.abs(track[0]!.lat) < 52);
61 true

What it prints (run when this page was built)

View sourceEdit on GitHubMade from the source of @johnmorrisdotca/chikyu-earth 0.51.1.