To provide an improved radar system for monitoring the runway invasion in an airport surely and more inexpensively than a current airport surface detection equipment(ASDE-3) system.

The inventive system comprises a radar system 20 including a plurality of radar sensors 13 arranged closely to a runway 11 and generating radar beams 13a for covering the entire runway while overlapping, a central processing unit 16 for receiving radar data from each radar sensor 13 and processing the radar data to generated a runway map for discriminating nearby targets and aircrafts, and an operator display 17 for displaying the map connected with the central processing unit 16. The radar sensor 13 is connected with an interface processor 14 for processing the radar data and delivers a data to the central processing unit through an RF remote measuring electronic unit 14a.