Ground station(QGC) <=> Pi <=> Pixhawk time sync using GPS?

We are using a Pi onboard the drone to run ROS and communicate with the Pixhawk and Ground station.
Currently, we are running ntp server on the ground pc and the time syncing the Pi with the ground station.
This requires internet, when operating in the field.

Is there a way to sync the time using GPS on the aircraft and/or the base station for RTK connected to the ground PC?

In MAVSDK we get the time from PX4 with the message UTM_GLOBAL_POSITION](https://mavlink.io/en/messages/common.html#UTM_GLOBAL_POSITION), also see: https://github.com/mavlink/MAVSDK/commit/ae9ac87fb07ba43b6c17bc4f1b839730a095c599.