 To create spatially appropriate climate data numerous stations and/or sensors are used to collect data which can then be interpolated over the landscape due to known interactions with elevation, aspect, slope, and distance to the coast or other water bodies using Geographic Information Systems (GIS).Instead of depicting a region as all one Winkler region (Napa Valley AVA being a Region III for example), spatial data summaries show the Napa Valley having a full range of Winkler regions, 12% a Region II, 56% a Region III, and 30% a Region IV (whereas the table above shows one station in Napa, St. Helena as being a Region IV).Other significant differences exist depending on the time period of the data and formula used for calculating growing degree-days.