Does GPS Work in the Snow?

Salespeople, truck drivers and other mobile professionals depend on Global Positioning System devices to help them navigate safely through their busy workdays. A GPS unit determines location based on radio signals it receives from satellites in space. The signals are relatively unaffected by weather conditions, so you can expect your GPS to provide reliable directions even in snow.

GPS Basics

 The U.S. Department of Defense originally developed the Global Positioning System during the 1980s as a way to coordinate military efforts. The system consists of a minimum of 24 satellites orbiting the Earth, each broadcasting its own precise time code signal. A GPS receiver picks up the signals from at least four satellites at any one moment; the combined information yields an accurate location in terms of latitude, longitude and altitude.

Weather Effects on Radio Waves

The atmosphere affects radio waves in a few different ways. The upper region, called the ionosphere, can reflect radio transmissions, and dust and moisture can absorb and scatter radio waves. A complex relationship exists between the wavelength of radio waves and how they interact with the atmosphere and weather. Airborne moisture, for example, absorbs some types of microwave signals, which have wavelengths of a few centimeters. AM radio, which has wavelengths of hundreds of meters, bounces off the ionosphere, allowing you to hear nighttime broadcasts from distant cities. GPS uses two radio frequencies, 1575.42 MHz and 1227.60 MHz, which have wavelengths of 18 and 24 centimeters. Rain and snow have little effect on these frequencies.

  

Weather and GPS Accuracy

According to the University of Colorado, changes in the troposphere, the lower layer of the atmosphere in which weather occurs, slightly affect the accuracy of GPS location data. Pressure, temperature and humidity across long distances can alter GPS readings by up to one meter. In terms of navigating through a town or across a state, one-meter accuracy poses no problems to most business users.

Snow and GPS

Because the military needs to function in all kinds of weather, the Department of Defense selected GPS radio frequencies that were unaffected by rain or snow. A snowstorm in progress does not absorb GPS signals, and snow and ice on the ground do not absorb or reflect them. You can rely on GPS directions in difficult winter weather because snow does not hinder the GPS unit's performance.