Line guidance during airborne acquisition is accomplished using Differential Global Positioning System (DGPS).

Final horizontal positioning of the aircraft during bathymetric operations is typically accomplished using DGPS or Post Processed Kinematic (PPK) GPS solutions. The SHOALS-1000T is equipped with both OmniStar and CSI Navbeacon DGPS receivers. If DGPS coverage is not available, if DGPS coverage is not reliable, if use of a geoid model is permitted or if topographic data are required on the same project, PPK GPS positioning may be required. For PPK solutions, one or more ground-based reference stations are required. This involves setting up at least one dual frequency kinematic capable GPS receiver over a geodetic control point at each station. If geodetic control does not exist within the project area, it must first be established by extending geodetic control to the project area. Final aircraft trajectories are computed in post-processing using Applanix's POSPac software. Here the ground-based dual frequency GPS data are combined with the airborne dual frequency GPS data from the NovAtel Millennium card in the POS AV. Reference station spacing will vary depending upon the shape and size of the project area, but the aircraft should never be more than 30km from a reference station while surveying. Surveys must be scheduled to avoid periods of high Dilution of Precision (DOP).

Final positioning of the aircraft during topographic operations is typically accomplished using PPK GPS solutions, as described above.

Operational Considerations:
Aircraft
Water Clarity
Weather
Horizontal Positioning
Vertical Positioning / Tides
Sensor Orientation
Airborne Lidar Data Acquisition
Quality Control