As a Chartered Land Surveyor my career has been involved with measurement using a variety of techniques and adopting new techniques as technology evolved and measurement using photographs (photogrammetry) has always been of particular interest. Photographs are a permanent record of the subject being measured which can be referred to again and again so measurements can be taken without site revisits. These pages contain information on some methods of measurement from photographs including Photographic Intersection and measurements from 360° Panoramas.
The Use of Spherical (360°) Panoramas for Photogrammetry Spherical Panorama projections are suitable for the extraction of measurements to compute the 3D co-ordinates for points from two or more panoramas.
The mathematics involved is much more straight forward than that required for using photographs for Stereo Photogrammetry and Photographic Intersection.
Horizontal and Vertical angles are easily measured in an Equirectangular projection to provide the same data as if a theodolite was used at the same location.
Accuracy for Intersection Solutions The accuracy for a point measured using an Intersection method is determined by three inter-related factors:
the separation of the Stations (Base Line),
the Angle of Intersection and
the Precision of the Angular Measurements.
Finding the Nodal Point of a Lens For a lens to be used effectively for Photographic Intersection and taking certain types of Panoramas, such as full 360° Panoramas, the location of the Nodal Point (or more correctly, the Entrance Pupil or No Parallax Point (NPP)) must be accurately determined.