UAS + Photogrammetry Reduces Cost and Risk of Surveys By Jerry Fireman President - Structured Information Needham Heights, MA
There are many civil engineering and environmental remediation applications that require survey data in hazardous areas where conventional survey methods aren’t effective. “Photogrammetry helps us win more jobs by providing more competitive pricing,” said Paul Lepine, Senior Geotechnical Technician for exp Services Inc., Burnaby, British Columbia. Using a drone UAS (Unmanned Aerial System) to acquire photos that can be used as the basis for accurate surveys is rapidly gaining traction as a preferred technique. Matt Sakals, Research Geomorphologist for British Columbia’s Ministry of Forests, Lands and Natural Resource Operations (FLNRO) added that “Combining a UAS with photogrammetric software makes it possible for us to efficiently complete difficult surveys in remote and rugged areas.”
Rock slope surveys
exp specializes in performing rock slope surveys that are required when rock slope remediation systems are built alongside highways. The company surveys the rock slopes and calculates the amount of mesh required to cover the slope and also proposed locations for metal stanchions used to secure the mesh. The company also estimates the required rock scaling -- the removal of loose rock from slopes – and shotcrete – concrete that is sprayed onto the rock slopes. One of the critical areas in the survey is at the joint planes formed by breaks of natural origin in the continuity of either a layer or body of rock. Water often invades cracks at the joint line or fracture. Later as the temperature drops and freezes the water, its volume expands. This expansion pushes the rocks on either side of the joint apart, breaking off pieces of rock that may fall onto the road.
In the past, exp surveyors used a total station to survey a few thousand points on a typical 100 meter long rock slope. This process normally took three days. One of their challenges was that the two-lane highways are typically only 15 meters wide and the rock slope cuts are commonly 30 to 50 meters high and sometimes up to 100 meters.