About GPS receivers
With a Global Positioning System (GPS) receiver connected to your computer or smartphone, you can see your current location on the MapPoint map. When a GPS receiver is installed, MapPoint checks for your location once every second and displays it on the map. You can configure the map to remain centered on your current location, to rotate to follow your travel direction, and to display a trail that shows where you have traveled. You can also use your GPS receiver to provide your location to the navigation feature when you are following directions that you obtained by creating a route with MapPoint.
In the GPS pane to the left of the map, you can view the latitude and longitude coordinates of your current location, your altitude, the most recent time your GPS receiver recalculated your position, the speed at which you are traveling, your compass heading, and the strength of the satellite signal. The latitude and longitude coordinates are also displayed in the lower-right corner of the screen when the pointer is within the map area. As you move the pointer around the map, the latitude and longitude coordinates change.
When using GPS tracking, GPS status information appears at the bottom of the screen in the status bar. The status information includes whether or not the GPS device is receiving data and the number of detected satellites.
Some versions of MapPoint include a Microsoft GPS device that is designed to work with the program. However, you can also use other GPS devices. To work with MapPoint, your GPS receiver must be compliant with National Marine Electronics Association (NMEA) standards, and its input/output format (interface) must be set to support the NMEA 0183 version 2.0 or later format. For more information, check the documentation that came with your receiver, or visit the NMEA Web site.
How a GPS receiver works
A GPS receiver takes in data from a constellation of 24 satellites that orbit the Earth. These satellites are arranged so that at least four are always visible in the sky from anywhere on Earth. A GPS receiver attempts to locate signals from at least three satellites, but preferably four or more. With these signals, your latitude and longitude, altitude, speed, and direction can be determined anywhere on Earth and in any weather.
Note Because a GPS receiver must track data from at least three satellites at the same time, there must be a direct line of sight to the sky when you use the receiver.
Locations are calculated through a process called three-dimensional trilateration, a mathematical formula that uses the positions of the satellites and their distance from the Earth (based on the amount of time the signal takes to reach the receiver) to determine the point at which the satellite signals and the surface of the Earth intersect. After the GPS receiver acquires the satellite signals, the receiver continually recalculates your position as you travel and provides that data to MapPoint as a series of latitude and longitude pairs that can be shown on a map.