This lecture covers the acquisition, decoding, and position calculation of GPS signals, focusing on the sources of errors such as the atmosphere (ionosphere and troposphere), receiver-related errors, and satellite tracking. The instructor explains the impact of atmospheric conditions like dry air and temperature on signal accuracy, as well as the challenges in modeling and correcting ionospheric and tropospheric delays. The lecture also delves into the calculation of satellite positions, receiver clock errors, and the process of determining the user's position using GPS data. Practical examples and comparisons between low-cost and high-precision GPS systems are provided to illustrate the importance of accurate signal processing.