One of three recognized methods of determining the average velocity of airflow along a mine roadway by anemometer. A velocity reading is taken at the center of the airway and the result is multiplied by the center constant, whose value ranges between 0.8 and 0.9, to give the average velocity of flow. Alternatively, the reading is taken along a midway line at a position some one-seventh to one-third of the width of the airway, measured from the side. At this position, the mean velocity is obtained, so that no adjustment is required. Compare: division method; traversing method.