Which type of GPS measurement allows for sub-meter accuracy but can couple with carrier phase for enhanced precision?

The type of GPS measurement that allows for sub-meter accuracy and can couple with carrier phase for enhanced precision is known as the Code Phase Signal. This type of measurement utilizes the pseudo-random noise code transmitted by GPS satellites to determine its position. Code phase measurements typically yield accuracy within one to two meters, but when combined with carrier phase measurements, which use the phase of the signal's waveform itself, the accuracy can be improved to the centimeter level.

The carrier phase measurements are often more precise than code phase but depend on the ability to resolve integer ambiguities. When the code phase is used as a preliminary estimate for positioning, it can significantly enhance the overall system's accuracy when paired with carrier phase techniques. This synergy allows surveyors to leverage the initial quick positioning from code phase while refining their data with the more precise carrier phase.

Other options present distinct functionalities and limitations:

• Autonomous GPS does not offer the higher precision achievable through carrier-phase measurements. While it provides basic GPS capabilities, it relies solely on code phase information and therefore has reduced accuracy compared to combined approaches.

• Carrier Phase Signal itself provides high precision directly but does not inherently offer the sub-meter accuracy or rapid initial positioning that code phase signals provide.

• Dual Frequency Signal enhances reliability and accuracy,