Stream Velocity Observation Velocity observation code. United States Geological Survey, Surface Water User Group UNSP 1 true unspecified The average velocity observation was not specified. 268D 2 true .2/.6/.8 depth The velocity observation of flow through a vertical section at 0.2, 0.6, and 0.8 depths. 2&8D 2 true .2/.8 depth The velocity observation of flow through a vertical section at 0.2, and 0.8 depths. .6D 3 true .6 depth The velocity observation of flow through a vertical section at 0.6 depth. .5D 4 true .5 depth The velocity observation of flow through a vertical section at 0.5 depth. VPRF 5 true velocity profile Velocity profile. SURF 6 true surface velocity The velocity observation of flow through a vertical section at the surface. ULTA 7 true ultrasonic path The ultrasonic path method is referring to the horizontal path used for monitoring a velocity index at a gaging station. .2D 8 true .2 depth The velocity observation of flow through a vertical section at 0.2 depth. SFLT 9 true surface float The velocity observation of flow using a surface float. DINT 10 true depth-integrated float The velocity observation of flow using a depth integrated float.