Physics for Game Developers, 2nd Edition

Chapter 22. Gaming from One Place to Another

Once a tool meant to help the United States guide intercontinental ballistic missiles, the Global Positioning System (GPS) has evolved to be a part of our everyday lives. The current generation will never have known a world where getting lost was something that couldn’t be fixed by trilaterating their position between satellites orbiting the planet. Although GPS has become commonplace in the navigational world, the proliferation of smartphones is just now opening the doors to GPS gaming. While this genre is just emerging, we’d like to give you an introduction to the physics behind GPS and the current applications in the gaming world.

Let’s recall that positions near the earth’s surface are generally given in the geographic coordinate system, more often described as latitude, longitude, and altitude. Latitude is a measure in degrees of how far north or south you are from the equator. Longitude is the measure in degrees of how far east or west you are from the prime meridian. A meridian is a line of constant latitude that runs from the North Pole to the South Pole. The prime meridian is arbitrarily defined as the meridian that passes through the Greenwich Observatory in the UK. Altitude is usually given as the measure of how far above or below sea level you are at the point described by latitude and longitude.

Location-Based Gaming

Before getting to the physics behind GPS, we’d like to take a moment to discuss how GPS is being implemented ...