GPS, or the Global Positioning System, offers a real-time position fix with an accuracy of 3 to 100 meters on a 24 hour per day basis. It also offers a way to determine time to a precision of better than a few hundred nanoseconds almost anywhere on the surface of the earth.

The GPS system consists of a constellation of 24 satellites. These satellites orbit the earth at an altitude of about 10,900 miles and at an inclination of 55 degrees. This orbit translates to an orbital period of 12 hours. The orbits are distributed around the earth in such a way that at least 6 satellites are always visible from virtually any point on the surface of the earth. This provides a means of precisely determining the position of the user in longitude, latitude, and altitude. These are capabilities that are revolutionizing many areas of life -- including entertainment. See our new section below on Geocaching!

• GPS FAQs from the US Government -- straight from the horse's mouth, all kinds of info on GPS
• An Introduction to the GPS System — Super explanation of GPS
• The Global Positioning System: Some Basics — Another good GPS tutorial
• Trimble's GPS Tutorial — Outstanding!
• Garmin's GPS Tutorial — From one of the industry leaders
• A Short Introduction: "About GPS" (press the GPS button on the menu bar)
• National Air and Space Museum Online Gallery for GPS
• US Coast Guard (The US Government Agency Responsible for GPS)
  — a general overview of missions and latest news
• U.S. Coast Guard Navigation Center GPS Page — a wealth of data on all aspects of GPS operations
• GPS - (Almost) Everything You Wanted to Know -- Information on GPS, including maps, background info, links, reviews, and more.
• GPS Information.Net -- Information on GPS from Joe Mehaffy and Jack Yeazel
• U.S. National Geodetic Survey
• U.S. Naval Observatory Navstar GPS Operations
• GPS World Online Magazine
• DMOZ Open Directory Project: GPS Information
• GPSy's GPS Resource Library
• Geodetic Survey of Canada
• Georgia Tech Aerial Robotics
• GLB Radio Data Systems
• Institute of Navigation
• International Aerial Robotics Competition
• Institute of Navigation (Alberta Chapter)
• Waypoint Consulting Inc.