A staff gage gives a quick estimate of gage height (stage) of a river

This is a picture of a staff gage. Staff gages can be installed either vertically or inclined and they allow for the stage, commonly referred to as the gage height, to be directly read by a hydrographer. The standard USGS vertical-staff gage consists of porcelain-enameled iron sections 4 inches wide and 3.4 feet long and graduated every 0.02 feet. Vertical-staff gages are set and calibrated by surveying directly to the staff gage. USGS streamgages use staff gages as reference during each field visit to verify the accuracy of the recording stage sensor that is published online. Other common types of reference gages include stilling wells, wire-weight gages, or other surveyed reference points.