This paper investigates the identification of slums in Medellín, Colombia, conducted by two independent research teams. By comparing two similar methodologies, based on Earth observation (EO) data and utilizing manual visual image interpretation (MVII), this study highlights overlaps and differences in the identified areas. The findings reveal significant congruence in core informal area zones but notable divergences in peripheral and less densely developed regions. These results underscore the necessity for transparent conceptual definitions of the target class 'slum', for transformation of conceptual approaches in mapping approaches, for the explanation of effects of ambiguities in both, and thus for the development of improved mapping protocols.