Surveying Glossary — Letter O

Oblique aerial imagery is remotely sensed photographic data captured from aircraft or drones at oblique angles to the Earth's surface, providing three-dimensional perspective views of terrain and built environments.

Offshore survey is the process of measuring, mapping, and documenting underwater and coastal features, bathymetry, and infrastructure in marine environments beyond the shoreline.

An optical plummet is a precision sighting device integrated into surveying instruments that aligns the instrument's vertical axis directly above a ground point using magnified crosshairs and a mirror system.

Orthometric height is the vertical distance from a point on Earth's surface to the geoid, measured along the direction of gravity.

An orthophoto is a geometrically corrected aerial or satellite photograph that has been adjusted to remove distortions caused by camera tilt and terrain relief, allowing it to be used as an accurate map.