Figure 5
From: Development of a Testbed for Wireless Underground Sensor Networks

(a) The structure and installation of paper pipes . (b) Use of paper pipes in 10 cm-diameter and 90 cm-depth holes for a temporary WUSN testbed.
From: Development of a Testbed for Wireless Underground Sensor Networks
(a) The structure and installation of paper pipes . (b) Use of paper pipes in 10 cm-diameter and 90 cm-depth holes for a temporary WUSN testbed.