G. Reitmayr, E. Eade, and T. Drummond. Localisation and interaction for augmented maps. In Proceedings of IEEE ISMAR’05, Vienna, Austria, October 5-8 2005. [pdf]
The paper presents a projection technique useful to augment maps and therefore the tangible interaction an user might have with the artefact itself. The basic assumption is that cartobraphic maps are complex visualizations that afford natural interaction by direct manipulation. They can be freely arranged, moved or annotated. A map also creates a common reference frame for multiple users in which gestures and verbal communication are interpreted.
The paper details the extremely sofisticated system they used to calibrate the projection from the top to the map raster. Everytime the map was moved, also the projected content was dynamically readapted.
Using extra devices or other technical solutions was possible to handle more complicated intertaction on top of the map: annotations with symbols, curves or areas; calculation of areas of occlusion or layering of different maps.