What is the difference between guided wave radar and non-contact radar?

We all know that there are waveguide radar and non-contact radar, so where are they used, what are the differences between the applications? 

Guided wave radar level meter uses probe rod immersed in process medium to guide low power nanosecond microwave pulse.

Note that the frequency of the radar level gauge usually refers to the carrier frequency. Guided wave radars do not use carrier frequencies like contactless radars, so there is no mention of frequencies.

The guide radar is mounted on top of the tank or bypass pipe, the guide rod usually extends to the entire depth of the vessel, and low-energy pulses of microwave are sent down along the guide rod at the speed of light. At the intersection of the guide rod and the liquid level (air/liquid interface), a significant proportion of the microwave energy is reflected back to the transmitter through the guide rod.

A second echo from the interface between the two liquids below the first liquid can be detected because a certain proportion of the pulse will continue down the guide rod through the fluid with low dielectric constant.

Because of this feature, wave-guided radar is ideal for measuring liquid/liquid interfaces, such as oil-water decomposition surfaces, as well as for situations where measurements are made through foam.

Guided wave radars can be used in containers of small geometric dimensions, bypass pipes and storage tanks of various sizes. Since a guided radar does not rely on a "flat" surface to reflect its echoes, the level gauge is suitable for measuring a wide range of powders and grains, as well as liquids whose surface is tilted by vortexes.

Non-contact radar level gauges are not easily corroded and are ideal for viscous, viscous and abrasive liquids. Non-contact radar level gauges are often used in containers with agitators. The HF radar is completely isolated from the process media by teflon seals and can be used with valves.