In LOS studies the earth curvature can be expressed or represented in 2 ways:

• The use of K-factor (beam)
• Calculations that use the surface refractivity (ground)

Depending on the requirements for your analysis or based on the frequency you can choose how the earth curvature will be displayed in RMpath.

Ground is used for VHF and UHF mobile communications wich are more based on statistics and have a limit for the coverage that is usually beyond the horizon, not LOS.

Beam is used point-to-point or microwave studies where you want to evaluate the LOS clearance and reflections at various K values.

Radio Mobile is known to be not a good tool for microwave studies.