What does this number measure?
The 1 192 km reference corresponds to a river-system convention extended upstream, not just the river named Mobile. The USGS explains that this type of measurement can follow the Alabama, Coosa, Coosawattee and Cartecay to Tickanetley Creek. The named Mobile begins only about 45 miles north of Mobile Bay. The illustrated map may show a subset of the available sections; the ruler separately compares the documented length of the system.
This length follows the course adopted by the catalogue. Maps show simplified, sometimes partial courses; an independent bar represents the documented length, distinct from straight-line distance.
Compare the stated dimensions
The comparison uses the number in each fact sheet: altitude, height, diameter, length or distance, depending on the reference. Two values in metres do not necessarily describe the same property.
Source and limitations
River-system convention: 1 192 km does not refer to the Mobile alone, which is much shorter. The upstream limits and generalisation of the map data affect the comparison.
Top view of a simplified geographic course of Mobile, based on the available mapped segments. The reference drawing may be partial, and river systems may combine several branches. River width and the textures of water and banks are interpreted; this is not a satellite photograph. Only the lower bar represents the documented reference length; the width of the map above does not measure that length. Course data: Natural Earth, public domain. License: Natural Earth public domain.