Final answer:
The requirements for selecting an alternate that only offers GNSS approach include having a device that supports GNSS technology, a GNSS receiver, compatible software or application, and access to a GNSS network.
Step-by-step explanation:
To select an alternate that only offers GNSS (Global Navigation Satellite System) approach, the primary requirement is to have a device that supports GNSS technology. This can be a standalone GPS device or a smartphone with GPS functionality. Additionally, the device should have a GNSS receiver capable of receiving signals from multiple satellite constellations such as GPS, GLONASS, Galileo, and BeiDou.
Furthermore, the device should have a compatible software or application that can interpret the GNSS signals and provide accurate positioning and navigation information. This software should have the capability to calculate position, velocity, and time information based on the satellite signals received.
Lastly, it is important to have access to a GNSS network or system that provides reliable and up-to-date satellite signal information. This ensures that the device can receive the necessary signals for the GNSS approach and accurately calculate the position.