An important aspect of a Dutch research project into usable (and well scaled) mobile maps for consumers is presented: the development of an appropriate field-based usability evaluation methodology for the prototype of a geo-mobile application that will be the result of a user centred design approach. Automatic generalisation, required for the user's orientation in space, but also for progressive data transfer, will be an important aspect of the prototype. What is reported here is an effective and technically unique user research methodology, based on a combination of video observation, thinking aloud and semi-structured interviewing. The experiments that have led to this outcome revealed some interesting usability issues that deserve further investigation
