08. Measuring: Assumptions

It is assumed that users of AragoJ are familiar with the basic principles of close-range photogrammetry theory. There are several excellent works on the theory and applications of photogrammetry as well as many on-line resources that can be found using a search engine. The Wikipedia entry on photogrammetry can be found here.

Presently, AragoJ assumes that pixels are square and, in consequence, that the conversion factor applies equally to the length and width of the image, which is an acceptable assumption for most current (2018) digital photographic cameras.

Measurements made by AragoJ also assume that images have no perspective [tangencial] (<~3° camera tilt ref object) and/or optical [radial] (barrel, pincushion, mustache) distortions, which is not realistic for most photographic images.

To ensure that the measurements are as accurate as possible, images should be taken in a way that avoids perspective distortion and images suffering from optical distortion should be processed to reduce or eliminate the distortion prior to any measurements being taken. If necessary, AragoJ has a module for camera calibration and image correction.

Finally, AragoJ IS NOT meant to be used in 3-D photogrammetry, and thus it cannot handle 3-D surfaces.