Definition of Bearing in GPS Navigation

How your GPS knows where you want to go

a GPS screen in car windshield, skyline ahead
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Your GPS bearing is the compass direction from your current position to your intended destination. In other words, it describes the direction of a destination or object. If you're facing due north, and you want to move toward a building directly to your right, the bearing would be east.

What Is the Definition of Bearing?

The definition of bearing predates GPS. Mathematicians were calculating bearing by hand for centuries before satellites made navigation as easy as pressing a button. Traditionally, bearing is measured in degrees and calculated clockwise from true north. It's typically represented as three figures. For instance, the bearing for the direction of east is 090°. 

Bearing and direction are not interchangeable terms. Bearing refers to the relationship between two locations, whereas directions refer to north, east, south, and west.

Bearing is sometimes called "true bearing" because of its relationship to true north. In GPS navigation, bearing may also be referred to as the "bearing to next waypoint."

Bearing in GPS Navigation 

The Global Positioning System (GPS) is a network of navigational satellites operated by the U.S. Air Force that transmits geo-location, time, and weather information to GPS receivers on earth. The U.S. government maintains the GPS system and allows free access to it. 

GPS functionality has become a common feature of most smartphones and many other modern electronic devices. Thus, the term "GPS" is often used broadly to reference devices with GPS capabilities rather than the Global Positioning System itself. All GPS software relies on the same underlying infrastructure, so no single GPS app is better at calculating bearing than any other.

When you enter your intended destination into a smartphone or another device, its GPS feature pinpoints where you are in relation to your destination. With that information, it can calculate your bearing or the direction you’d take to move toward your destination.

Your bearing is calculated to the nearest degree, and it is typically the most direct route from Point A to Point B. Some device maps offer alternative routes to a destination, but your bearing would remain essentially the same because your destination is still a certain direction away from your current location, regardless of the route you take.

How Is Bearing Calculated?

Bearing is calculated as an angle measured in degrees in a clockwise direction from true north. The angle's vertex represents your current location, while the two rays point north and toward your goal destination, respectively. You can manually calculate the bearing between two points using a map, a compass, and a protractor; however, if you know the exact latitudes and longitudes of the points in question, you can use the following formula: 

β = atan2(X,Y)

First, you must calculate X and Y like so:

X = cos θb * sin ∆L

Y = cos θa * sin θb – sin θa * cos θb * cos ∆L

Whereas:

  • L represents longitude.
  • θ represents latitude.
  • β is the bearing.

Fortunately, GPS technology allows your phone to crunch complex equations like these within seconds.

Why Is My GPS Pointing Me in the Wrong Direction?

If you use the GPS on your phone to navigate, you may notice that the direction you're traveling in and the compass are not always in sync, especially if you are standing still or moving slowly. That's because GPS-enabled devices calculate bearing before they calculate the direction of travel.

GPS-enabled devices calculate bearing based on the target coordinates and the GPS receiver's present location. Next, the GPS determines the exact direction you must travel by measuring your position at approximately one-second intervals. If you are stationary or moving very slowly, the direction of travel cannot be calculated, so measurement errors can occur. Once you are moving at a consistent speed, then your GPS becomes extremely reliable. Due to the virtual infallibility of the Global Positioning System, your GPS device will always accurately calculate bearing; however, it may occasionally take you in the wrong direction.

Keep in mind that your GPS must also consider the accessibility and conditions of roads, so it might appear to be sending you in the "wrong" direction even when you are on the right path.