The hemisphere, longitude and latitude are used to calibrate FWI Calculator in terms of expected monthly "Daylight" ratios for the regions global position, and some expected leaf & duff moisture constants. These are used in calculations of Drought Code (DC) and DUFF MOISTURE CONTENT (DMC). Unfortunately it doesn't take into account terrain, such as mountains shading your location, however this is somewhat compensated for by the collected "micro" weather data.