In 2006, a collaborative effort between Geophysical Survey Systems and the Maine Department of Transportation found a 2 GHz air-launched horn antenna to be an effective tool for providing accurate assessments of the condition of bridge decks. The air-launched horn antenna and a 1.5 GHz ground-coupled antenna were used to evaluate the condition of an asphalt overlaid bridge deck located in Lewiston, Maine. GPR data lines were acquired at 2-foot intervals by walking the ground-coupled antenna system and by driving a vehicle with the air-launched horn antenna system.

The data was processed with GSSI’s Radan software program using the Bridge Assessment Module. The results were used to produce color-coded deterioration maps of the bridge deck. Results from both antennas in comparison demonstrated excellent correlation. The deterioration maps from both antennas compared with visual data obtained from top-side and bottom-side visual inspections exhibited excellent correlation.

The Maine DOT further confirmed correlation by hammer sounding and, finally, by opening the bridge deck to expose the actual areas of deterioration.