How accurate is GPS technology?

Question: I noticed that the history trail of one of my vehicles follows the road with great accuracy until it enters a heavy tree covered area, at which point it begins to slightly deviate from the road. Although I can see that the route generally follows the shape of the road, it does so with much less precision. Why does this happen? How GPS Units Track Data A GPS unit receives data from GPS satellites that orbit 12,000 miles above the earth. There are 24+ GPS satellites orbiting the earth at any one time. GPS satellites send satellite location, time, and satellite health information using standard radio frequencies. The GPS unit picks up these radio frequencies, and calculates its location based on triangulation between at least three satellites. This calculation is heavily dependent on time information sent by the satellite, as the time between transmission and receiving of the signal…