When talking about mobile AR today, and AR implementations in general, the
most widely adapted technology is marker tracking. This technology works by
having the camera detect and track physical markers in the environment, and
displaying virtual objects on the screen aligned to the markers. It has become
very wide-spread due to how easy it is to calculate the angle of the camera relative
to the marker and align the virtual object accordingly [7]. The virtual objects
could be 3D models, information, audio or video stream, or basically anything
else that can be created digitally. The early popularity of marker based AR came
in large thanks to Hirokazu Kato who developed the ARToolkit [8], a now open
source framework for AR and marker tracking that has seen several hundred
thousand downloads and has evolved into several spin-offs that are optimized
for mobile versions