In a conventional GNSS RTK survey, the data transfer from the base to the rover can be made either through a ______ or a telephone link.

In a conventional GNSS RTK (Real-Time Kinematic) survey, the use of a radio link for data transfer between the base station and the rover is integral to the operation of the system. This method allows for real-time transmission of correction data, which is crucial for achieving high positional accuracy in dynamic surveying applications.

Radio links are commonly used because they are reliable and can provide a direct connection without the need for intermediate systems. They operate over various frequencies, and their range can be adjusted to suit the survey environment, making them versatile for different field conditions. This technology supports data rates that are adequate for the rapid updates needed in RTK systems, ensuring that the rover can receive real-time corrections to its positioning.

Other options like television, facsimile, and telegraph are not suitable for the data transfer needs of GNSS RTK surveys. Television is primarily for video transmission, facsimile for document transmission, and telegraph is an outdated form of communication that does not support the real-time data transfer required for GNSS applications. Thus, the effective choice is a radio link, which is tailored for the specific requirements of the survey system.