Which statement best describes the difference between RTK and standard DGPS in terms of corrections and ambiguity resolution?

• A. RTK uses carrier-phase corrections and resolves integer ambiguities to achieve centimeter-level accuracy in real time; DGPS uses code-based corrections with limited accuracy.
• B. RTK relies on code-based corrections with centimeter-level accuracy, while DGPS resolves integer ambiguities in real time.
• C. RTK does not perform ambiguity resolution, while DGPS resolves carrier-phase ambiguities.
• D. RTK uses multiple frequency corrections only for broadcast corrections, whereas DGPS uses carrier-phase ambiguity resolution.

Answer: (A)

The main idea being tested is how precision is achieved in RTK versus standard DGPS, focusing on the measurements used and the ambiguity resolution.

RTK achieves centimeter-level accuracy in real time by using carrier-phase observations and actively resolving the integer number of carrier cycles, known as integer ambiguities, between the rover and the reference station(s). By solving for these ambiguities across multiple satellites and baselines, RTK tightly constrained the solution, producing very high precision in real time. The corrections sent from the base (or a network) include information that allows the rover to fix these ambiguities and refine its position accordingly.

Standard DGPS, on the other hand, relies on code-based pseudorange corrections. These corrections improve the range errors but do not involve resolving carrier-phase ambiguities. As a result, the achievable accuracy is lower—typically decimeter to meter level—because the carrier-phase ambiguities remain unresolved and the solution depends mainly on improved pseudorange measurements rather than resolving the integer ambiguities.

So, the best description is that RTK uses carrier-phase corrections and resolves integer ambiguities to reach centimeter-level accuracy in real time, while DGPS uses code-based corrections without resolving those ambiguities, leading to less precise positioning.