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.
Use 360° Panoramas for ‘Real Life’ Measurement PaMe provides two applications for getting measurements from 360° Panoramas. PaMe Wizard is a Krpano add-on providing a ‘measure tool’ in a ‘Krpano driven’ Virtual Tour. This full version contains four ways of measuring, with the ability to save the calibrations (which can be ‘locked’) and provide ‘real time’ measurements. PaMe Lightis a web based tool that allows you to just drag and drop your 360° Panoramas from your desktop. This light version has three ways of measuring.
PaMe – Measure from 360° Panoramas Some notes on using PaMe.
PaMe is straight forward to use with ‘on screen’ instruction and good tutorials so there is NO ‘steep learning curve’.
PaMe Light is excellent for experimenting with the application before committing to purchase PaMe Wizard.
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.
Single Lens v Multi-lens Cameras for Accuracy
Today there is a plethora of multi-lens cameras for capturing 360° panoramas which have the advantage of a single shot rather than taking a set of shots, but would these have the accuracy required for measurement as there are two fundamental differences between the two methods.
To make panoramas with a camera with a single lens it is usually mounted on a panohead and rotated about the NPP but with a multi-lens camera this is physically impossible.
Samsung Gear 360 + Insta360 ONE X The result of the investigating the accuracy of using a Samsung Gear 360 for measurement, where the Samsung Gear 360 was rotated around its central vertical axis and stitched with PTGui, which provided a more accurate result than combing the hemispheres with ActionDirector, raised the question “Would a better result be achieved if the Samsung Gear 360 was rotated about the NNP of the lenses?”
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.