Which of the following are major sources of error in GPS measurements that may be attributed to the receiver?

• A. Ionospheric delay
• B. Satellite clock bias
• C. Multipath interference
• D. Multipath and receiver noise

Answer: (D)

Receiver-related errors come from the hardware and local environment around the antenna. Two main issues here are multipath interference and receiver noise.

Multipath occurs when the GPS signal reflects off nearby surfaces before reaching the antenna, causing the received signal to take a longer path or arrive with a shifted phase. This distorts both the code and carrier measurements, leading to biases in the calculated range to the satellites.

Receiver noise comes from the front-end electronics, thermal noise, quantization, and other instrumental effects inside the receiver. These random fluctuations degrade the precision of the pseudorange and carrier-phase measurements.

External sources like ionospheric delay and satellite clock bias originate outside the receiver: the ionosphere changes the signal as it travels through the atmosphere, and the satellite clock bias comes from the satellite’s onboard clock. While these affect GPS measurements, they are not receiver-origin errors.

So, the combination of multipath and receiver noise best represents errors attributable to the receiver itself.