What began as a four member consortium has now added neighboring Effingham County and Bryan County. Current efforts will add water, sewer, and storm water system coverages. An important missing detail has been county-wide contour information. The schedule and cost restraints in the RFP could only be met using laser technology. Not only had the price plummeted compared to conventional techniques, the entire mapping could be completed in less than a year.
Flight planning determines optimal ALTM settings and aircraft parameters.
From an aircraft flying a regular pattern over the survey area, a focused, infrared laser, eye-safe at survey altitudes, sends up to 5,000 pulses per second to the ground below. A high accuracy scanner sweeps the laser pulses across the flight path and collects the reflected light. A laser range-finder, consisting of high precision discriminators and interval meters, measures the time between sending and receiving each laser pulse to determine the ground elevation below. While the laser signals are collected, a digital color video camera records the area being scanned by the laser and encodes the video image with a time tag. As the laser and video data are collected, a differential GPS receiver monitors aircraft position and an inertial reference system reports key aircraft data such as roll, pitch, and heading 50 times per second.