Which components are typically used together to establish project coordinates in GNSS surveying?

• A. A single handheld GPS unit without reference points.
• B. Ground-based control monuments and Continuously Operating Reference Stations (CORS).
• C. A tape measure and compass.
• D. Aneroid barometer.

Answer: (B)

Establishing project coordinates with GNSS relies on anchoring measurements to a precise reference framework. Ground-based control monuments provide fixed, surveyed points with known coordinates in the project datum; they serve as local anchors for distributing coordinates across the site. Continuously Operating Reference Stations (CORS) supply corrections and stable reference coordinates tied to the national/global datum, enabling accurate positioning of GNSS observations either in real time or through post-processing. Using both together ensures that the project points inherit the same coordinate system and the horizontal and vertical accuracies of the network, reducing local errors from satellite geometry, multipath, and atmospheric effects. Without reference points, a single handheld GPS cannot establish reliable project coordinates; a tape measure and compass are traditional tools that do not yield GNSS-based coordinates; an aneroid barometer is not used for determining project coordinates in GNSS surveys.