Have a look, if you haven't already, at these visualisations...

http://www.aaronkoblin.com/work/flightpatterns/

http://zengwei81.wordpress.com/projects/interchange-visualization/

http://colorbrewer2.org/

Ruth Conroy's method for mapping line of sight

Ruth Conroy's museum map

The two last ones are from: Conroy, R. (2001). Spatial navigation in immersive virtual environments. (PhD), University of London, London.