Error sources for GPS usage are a. Satellite clock b. Ionosphere c. Receiver clock d. Satellite orbit e. Lower atmosphere f. Multipath. Which of the following is NOT listed as an error source?

Error sources for GPS usage are a. Satellite clock b. Ionosphere c. Receiver clock d. Satellite orbit e. Lower atmosphere f. Multipath. Which of the following is NOT listed as an error source?

• A. Satellite clock
• B. Ionosphere
• C. Receiver clock
• D. Atmospheric refraction

Answer: (D)

In GPS, the typical error sources fall into satellite clock, satellite orbit (ephemeris), receiver clock, ionospheric delay, tropospheric (lower atmosphere) delay, and multipath. Atmospheric refraction is not listed separately because its effects are encompassed by the tropospheric delay models used to correct signals as they pass through the lower atmosphere. So atmospheric refraction is the item that isn’t listed as a separate error source. For context, the other factors correspond to distinct error sources: satellite clock and orbit errors come from the satellite’s timing and ephemeris data, receiver clock error from the local oscillator, ionospheric delay from the ionized layer, and multipath from signals reflecting off surfaces before reaching the receiver.

In GPS, the typical error sources fall into satellite clock, satellite orbit (ephemeris), receiver clock, ionospheric delay, tropospheric (lower atmosphere) delay, and multipath. Atmospheric refraction is not listed separately because its effects are encompassed by the tropospheric delay models used to correct signals as they pass through the lower atmosphere. So atmospheric refraction is the item that isn’t listed as a separate error source. For context, the other factors correspond to distinct error sources: satellite clock and orbit errors come from the satellite’s timing and ephemeris data, receiver clock error from the local oscillator, ionospheric delay from the ionized layer, and multipath from signals reflecting off surfaces before reaching the receiver.