The first stage after collection of a airport runway or taxiway is laser meshing. The first step in meshing is producing an accurate track of the vehicle's position, by combining reference station based GPS measurements and IMU measurements. When scanning an airport, obtaining and maintaining GPS phase lock is very important. Due to the lack of tree coverage this is easily achieved.
Detailed algorithms optimally combine the GPS and IMU measures taking into account such factors as GPS accuracy, IMU bias and drift as well as their changes throughout the scan. Once the position and orientation of the vehicle is known for each point in time, the laser profile measurements can be formed into a 3D mesh. We also perform further position corrections, by slightly adjusting the surface heights so that any GPS height error is eliminated between the multiple runs down the pavement. Filtering to remove the effects of grooves on the runway surface is also done at this point in time. The typical resultant mesh has a data density of 5 meters in the direction of travel, and 10cm across the runway. Higher mesh densities can be produced if required.