What does the following sentence mean, especially "in extent"
Two final reasons for a feature-based approach arise from its inherent discretization of the environment. First, Features are localized in extent, and feature size can be matched to sensor footprint.
I know the meaning of extent but I'm not able to comprehend its meaning in the aforementioned sentence. Features here mean landmarks or physical objects in the field of mapping and navigation (e.g. a tree).