Drilling Hole Monitoring by Koden, model : DM-604, 604R and 604RR, can measure and confirm for underground foundation work, the state of wall surface, pile diameter, deflection and incline, namely the "vertical accuracy" of the drilled hole or excavated wall. The deviation of the bore hole or trench from the perpendicular and any surface cavities in the bore hole or trench wall are measured. The ultrasonic measurement probe is suspended vertically from a cable and lowered into the object to be surveyed. At the same time, orthogonal waves are continuously emitted from the device and reflected from the walls. The reflected waves are registered by measurement sensors. The distances, calculated as a function of wave speed and reflection time, are presented in graphic form.