Final vertical positioning during bathymetric operations is typically accomplished using tides or water level data. Where bathymetric data are required relative to a tidal datum, the use of tidal data are most often required. Depending upon the specification, this could involve predicted tides, observed tides from a public domain source or observed tides from a project specific tide gauge. If a local gauge is required, it may be necessary to "tie-in" to an established vertical benchmark. It may be possible to derive bathymetry data relative to a tidal datum without actually collecting tidal data, if the relationship between the tidal datum and the ellipsoid is well known within the project area. In this case, ellipsoid elevations would first be computed using PPK GPS solutions and a geoid model would be applied to shift the vertical elevations to the geoid.

Final vertical positioning 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