Navigation of an instrument within a luminal network can include image-based branch detection and mapping. Image-based branch detection can include identifying within an image one or more openings associated with one or more branches of a luminal network. Image-based branch mapping can include mapping the detected one or more openings to corresponding branches of the luminal network. Mapping may include comparing features of the openings to features of a set of expected openings. A position state estimate for the instrument can be determined from the mapped openings, which can facilitate navigation of the luminal network.