Two. The 15km transmission distance can only be attained under the FCC standard when measured in an out of doors natural environment with out interference. The SRRC standard is adopted in mainland China, as well as furthest transmission distance is 8 km. Mavic 3M with RTK module for centimeter-amount positioning. https://m3mhomes.com/dwarka-expressway-project-will-be-completed-soon-gadkari/