Expert on maps, cartography, their history, and their cultural, social, and technical relations. The theory of representation.
- Mapping of colonial North America
- Cultural and social significance of maps, both in the past and present
- Technologies and processes of surveying and mapping
- President, American Friends of the JB Harley Research Fellowships, which raises funds to assist in research and to attend conferences in map history
- Osher Professor in the History of Cartography (University of Southern Maine)
- Trustee of the Internal Society for the History of the Map (ISHM)