Fig. 7: Photographs of the site survey.

a Leeb hardness tester (COY TH110); b Surface hardness testing of rockery; c Portable ultrasonic detector (Proceq Pundit Lab+); d The ultrasonic testing of rockery.

a Leeb hardness tester (COY TH110); b Surface hardness testing of rockery; c Portable ultrasonic detector (Proceq Pundit Lab+); d The ultrasonic testing of rockery.