Surface weather analysis United States, temperature and dewpoint are plotted in degrees Celsius. The wind barb points in the direction from which the wind is coming. Each full flag on the wind barb represents of wind, each half flag represents . When winds reach , a filled in triangle is used for each of wind. In the United States, rainfall plotted in the corner of the station model are in inches. The international standard rainfall measurement unit is the millimeter. Once a map has a field of station models plotted, the analyzing isobars (lines of equal pressure), isallobars (lines of equal pressure change),
Moody chart (Pa) (or head loss, "h" (m)) and flow rate through pipes. Head loss can be calculated using the Darcy–Weisbach equation in which the Darcy friction factor "f" appears : This formula must not be confused with the Fanning equation, using the Fanning friction factor "f", equal to one fourth the Darcy-Weisbach friction factor "f": Pressure drop can then be evaluated as: or directly from where "ρ" is the density of the fluid, "V" is the average velocity in the pipe, "f" is the friction factor from the Moody chart, "L" is the length of the pipe and "D" is the