02 / WHY IT WORKS

MEO: motion across the sky

Medium Earth orbits support broad coverage with multiple orbital planes. GPS, Galileo and GLONASS use MEO constellations. Their satellites move relative to a ground observer. The experimental MEO is an illustrative circular orbit; it does not replicate a complete operational constellation.

GEO and IGSO: synchronized period, different paths

A circular equatorial geostationary orbit has Earth’s sidereal rotation period and appears fixed above one longitude in the ideal case. An inclined geosynchronous orbit shares that period but moves north and south, making a looped ground track. BeiDou combines orbit classes; QZSS and NavIC use geosynchronous configurations for regional goals.

03 / UNDER THE SURFACE

From intuition to a model

From orbital phase to ground track

The experiment rotates a circular inclined orbit into an Earth-fixed frame. Latitude comes from the vertical component; Earth rotation is subtracted from inertial longitude. Longitudes wrap at ±180°, so the plot splits lines at the date line instead of drawing a false line across the map.

φ=arcsin⁡(sin⁡i sin⁡u)\varphi=\arcsin(\sin i\,\sin u)λ=atan2⁡(cos⁡i sin⁡u,cos⁡u)−ωEt+λ0\begin{aligned}\lambda&=\operatorname{atan2}(\cos i\,\sin u,\cos u)\\&\quad-\omega_E t+\lambda_0\end{aligned}

i: inclination; u: orbital phase; ωE: Earth rotation rate; λ0: reference longitude. Spherical Earth, circular orbit, schematic parameters.

04 / A WORKED EXAMPLE

Same period, different ground track

Select GEO and play one sidereal-day cycle: the ground point remains fixed in this ideal model. Switch to IGSO at 55° inclination with the same period. Its ground point now moves between about 55° north and south. This isolates inclination; real regional designs may also use eccentricity and different phasing. Switch to MEO to see a non-stationary longitude as well.

Return to the experiment and try it ↑

05 / PUT IT TO WORK

Try it in GNSS View

  1. Select a system in observation settings.
  2. Compare predicted sky positions at your location over time.
  3. Consult official service information and receiver specifications before assuming signal availability.
Open the observatory ↗

06 / COMMON QUESTIONS

Is GNSS the same as GPS?

GPS is one GNSS. Multi-GNSS reception combines compatible observations from more than one system.

Does a stationary satellite stop moving?

It still orbits Earth. Its apparent fixed position is relative to the rotating ground in the ideal GEO case.

Will every phone use every visible satellite?

No. Receiver hardware, supported signals, service status and environment all matter.

07 / FURTHER READING

An original GNSS View explanation. These references document the models, terminology and system context.

GPS.gov · Space segment ↗European GNSS Service Centre · Galileo ↗BeiDou Navigation Satellite System · Official portal ↗GLONASS Information and Analysis Center ↗Cabinet Office, Japan · QZSS technical information ↗ISRO · NavIC ↗International GNSS Service · MGEX constellations ↗