FTP identify the type of device used to measure cloud bases.
The scanning receiver type has its light transmitter fixed to direct its beam vertically and the parabolic collector scans up and down the vertical beam searching for the point where the beam intersected the base. The rotating transmitter type has its separate receiver fixed to direct reflections from directly overhead while the transmitter sweeps the sky. FTP identify the type of device used to measure cloud bases.
The scanning receiver type has its light transmitter fixed to direct its beam vertically and the parabolic collector scans up and down the vertical beam searching for the point where the beam intersected the base.
ceilometer