Which error in GPS occurs due to obstructions like trees and buildings?

Multipath error occurs when GPS signals bounce off obstructions such as trees, buildings, or other surfaces before reaching the GPS receiver. This reflected signal can cause inaccuracies in the calculated position because the time it takes for the signal to travel to the receiver is altered when it takes a longer path due to reflection. The GPS receiver interprets these delayed signals as coming from a different position, leading to errors in determining the actual location.

Obstructions not only create the potential for multipath effects but can also weaken the signals received, making the correction and interpretation of the data more challenging. In contrast, other types of errors, such as tropospheric delay, arise from atmospheric conditions affecting signal propagation, satellite drift relates to the positioning and timing of satellites in orbit, and receiver noise is related to the electronic components of the GPS receiver itself. These errors do not directly result from physical obstructions in the environment as multipath error does.