Longwall Retreat and Creep Measurement Based on UWB Radar Imaging Method

Figure 7

The radar imaging results at 0.15 m and 0.30 m heights before and after the advancing of longwall face. (a) 0.15 m before the advancing, (b) 0.30 m before the advancing, (c) 0.15 m after the advancing, and (d) 0.30 m after the advancing.

(a)

(b)

(c)

(d)