Question 461Navigation General

The correct answer is D) black dot. On Army Corps of Engineers navigation maps for the Lower Mississippi River, each mile Above Head of Passes (A.H.P.) is marked by a black dot on the map. This is the standard convention used to denote mileage markers on these navigation charts. The other answer choices are incorrect because: A) navigation lights are physical markers on the river, not map symbols; B) dashed red lines are not used to mark mileage on these maps; and C) while the maps do show numerical mileage, the mileage is not indicated by a number at each individual mile marker.