Proposal 1
The mapping of Eixample can be driven by the pedestrian movement at different times of the day.
For example the corners of an Eixample with a restaurant would have more footfall rather than an Eixample with a warehouse or containment storage facility (the only pedestrian movement such corners will have is the people who HAVE to cross that corner to reach someplace else. Also the restaurant corners would have more footfall during lunch time than any other time of the day and so on.
Proposal 2
The fallen dead leaves piled up at different places in an Eixample could be another way to map the use of that space. Where dead and crushed leaves would suggest more footfall or vehicular movement (on the road), the crisp and unreformed dead leaves would suggest else wise.
Proposal 3
Different age groups have different preferences in terms of use of a public space. While the elderly walk away from the footpath edges the young might make way for the shortest route possible. Mapping the different routes taken by pedestrians(long or short) within different age groups can be used to map the Eixample.