In GNSS surveying, the direct _____ has to be with the satellites and not with the stations in the project ______network.

• A. communication, planning
• B. line of sight, planning
• C. communication, control
• D. line of sight, control

Answer: (D)

In GNSS surveying, observations come from the line-of-sight path between satellites and the receiver. The signals travel directly from each satellite to the receiver, and the measurements (like pseudorange and carrier-phase) rely on that unobstructed line of sight. The project’s control network of ground stations provides reference coordinates and constraints for adjusting the network, but there isn’t a direct line-of-sight measurement between these stations themselves. So the essential requirement is that the direct line of sight is with the satellites, not with the stations in the control network. That’s why the best fit is line of sight and control.