The study of urban dispersion on a local scale requires the adoption of operational concepts. This research uses the notion of "Base Land Unit" (BLU), which represents a functional and experiential reality.

The current paper presents an explanation of this concept and a methodology to distinguish BLU of dispersed occupation from other types of Units (concentrated, unbuilt…).

The developed methodology comprises three different methods:

- Identification of Building Ensembles by Digital Method;

- Calculation of the Disaggregation Index of Continuous Building Ensembles;

- Criterion for Identifying BLU of Dispersed Occupation.

A detailed description of each phase is presented, as well as the results of its application in the case studies of the Research Project (Évora and Aveiro-Ílhavo).