Terrestrial lidar scan at Bob Hall Pier: Corpus Christi, Tx  By: Melinda Martinez                               Throughout summer, CMGL lab has been experimenting with the terrestrial light detection and ranging (lidar) laser scanner borrowed from North Carolina State University by scanning different environments. At Bob Hall Pier near the beach, the high tides made for an interesting scan since water reflects the laser beam in different directions.   On Wednesday, July 17th, Alistair Lord, Dr. Michael Starek, Mukesh Subedee, and Melinda Martinez of the CMGL lab conducted lidar scans on the beach near Bob Hall Pier in Corpus Christi, TX (Figure 1 and 2). The purpose of the trip was originally to scan the marsh field on Mustang Island, but the site was flooded due to heavy rain all morning. This would have made it difficult to get an a 3-D model of the marsh because of the way water reflects the laser. Skies were much clearer near Bob Hall Pier, so a scan was performed before the rain started again.  Figure 1. A 3D x,y,z point cloud from the laser scanner. Points are colored by the RGB (red, green, blue) pixel values obtained from the image acquired by the scanner’s co-aligned internal digital camera Figure 2. Panoramic digital image of Bob Hall Pier from the co-aligned internal digital camera. Image shows a section of the 360 degree field of view. Once a location was chosen, the field crew set up the equipment and began collecting data (Figure 3). The lidar scanner was set on a tripod leveled to the ground. Two GPS markers, consisting of a steel rebar and a styrofoam ball at the end, were set on each side of the scanner to be used as a reference point for the site. Once everything was connected and powered, the scan began with an initial wait time of 30 minutes, but this didn’t include the time it takes for the scanner to rebalance on the tripod. The collection time varies depending on how detailed the image is set on the computer. More detail requires shooting more points, which could possibly take up to 3 hours.  Figure 3. Image showing the Leica ScanStation 2 terrestrial laser scanner, scanner battery, and the scanner laptop used to operate the scanner and record the data. The lidar scanner emits a laser that reflects vertically by a rotating mirror and can be set to scan 180˚ or a full 360˚, the latter was set to for this site. The scan produces a 3D model of the area with a range of 250 meters scanning everything in sight, including people. Only one scan was performed on this day due to rain.