Model-Based Deep Line Utility Survey

By John W. Jaeger, Senior Project Manager, Binkley and Barfield Inc. | April 2014, Vol. 69 No. 4

Optimal Ranging Inc. (ORI), Santa Clara, CA, manufactures geospatial utility surveying equipment that provides highly accurate utility location and survey. The equipment is operated using Trimble Access controllers running a Trimble-supplied application called Utility Survey. ORI’s Dual Spar system was selected for its ability to render 3D highly accurate X, Y and Z locations of deep utilities without excavation or line incursion.

Since excavation was not necessary for this SUE QL-B work, BBI was able to immediately go to work without the need to make a call to the area one-call or utility notification center and wait 48 hours. BBI directly connected a low frequency (98 Hz), high output transmitter to the water line test station. The Base and Rover Spar units were then placed perpendicular to the water line, with spacing determined by the anticipated water line depth, using an approximate geometry that would render an equilateral triangle enclosing all three points (Base Spar, Gas Line and Rover Spar). After turning on the Spar units, achieving satellite lock, connection to the Trimble VRS System on the Trimble TSC3 Data Collector, the water line and its orientation appeared on the screen along with the signal strength and confidence level of the data. Geospatial data collection of ground level, offset location, utility location and utility depth were done by simply pushing a button.
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To get a smooth profile of the water line, data was collected at eight to 10-foot intervals. After recording all this data, the transmitter was removed from the test station and reconnected to another test station on the other side of the area to be designated (designating from two directions). This entire procedure was repeated on the gas line that was inaccessible to a vacuum truck.

The data collection work on the two lines was completed in less than four hours and did not require any surface restoration or probing. The resulting horizontal and vertical positioning from the data matched the utility location information and was delivered much faster and at a much lower cost than QL-A Test Hole excavation.