  Cosmic ray muons prove valuable across various fields, from particle physics
experiments to non-invasive tomography, thanks to their high flux and
exceptional penetrating capability. Utilizing a scintillator detector, one can
effectively study the topography of mountains situated above tunnels and
underground spaces. The Hankuk Atmospheric-muon Wide Landscaping (HAWL) project
successfully charts the mountainous region of eastern Korea by measuring cosmic
ray muons with a detector in motion. The real-time muon flux measurement shows
a tunnel length accuracy of 6.0 %, with a detectable overburden range spanning
from 8 to 400 meter-water-equivalent depth. This is the first real-time
portable muon tomography.
