# Why are GPS satellites so high?

## Why are GPS satellites so high?

The main reason they are in such a high orbit is to allow for more of the Earth to be visible at any one time. In order to have a reasonable amount of the Earth visible, you have to be high up.

How do satellites know their altitude?

All modern satellites use GPS in LEO. Not only to know the position, but sometimes even more important to have a very high accuracy clock! The GPS availability ends above the altitude of the GPS constallation (20,180 km – 12,540 mi).

### Are GPS satellites in geostationary orbit?

The Global Positioning System (GPS) is a constellation of about 24 artificial satellites. The GPS satellites circle the Earth at an altitude of about 20,000 km (13,000 miles) and complete two full orbits every day. The GPS satellites are not in a geostationary orbit, but rise and set two times per day.

How many satellites do you need for altitude?

The GPS satellites orbit at an altitude of about d = 20,000 km. Using the equation above, each GPS satellite can only “see” about 38% of earth’s surface in a given instant. Therefore, you would need a bare minimum of three GPS satellites in order to “see” the entire globe at once.

#### How fast do GPS satellites travel?

about 9,000 mph
Satellites move at about 9,000 mph—enough to make their onboard clocks slow down by 8 microseconds per day from the perspective of a GPS gadget and totally screw up the location data.

What altitude do satellites orbit in miles?

below your horizon. Mid-Earth orbit (MEO) is one in which a satellite completes a single revolution every 12 hours. MEO satellites orbit at altitudes around 12,700 miles (20,400 km). Global Positioning System (GPS) satellites populate this region.

## What altitude is geosynchronous orbit?

37,000 km
To attain geosynchronous (and also geostationary) Earth orbits, a spacecraft is first launched into an elliptical orbit with an apoapsis altitude in the neighborhood of 37,000 km. This is called a Geosynchronous Transfer Orbit (GTO).

Does GPS use time dilation?

This time dilation effect has been measured and verified using the GPS. The effect of gravitational frequency shift on the GPS due to general relativity is that a clock closer to a massive object will be slower than a clock farther away.