Improved Algorithms for Combining Satellite Imagery and Geographic Basemaps
Two new algorithms are now being used by the University of Wisconsin-Madison for combining real-time satellite imagery with basemaps. The first algorithm addresses the problems of the traditional method by utilizing surface temperatures (Tsfc) from observations or numerical models. Making the simple assumption that Tir<Tsfc over cloudy regions and Tir=Tsfc over cloud-free regions, one can create a map of transparency using Tsfc-Tir, where the opacity of the cloud increases as the value Tsfc-Tir increases. Comparisons of the traditional and new algorithm will be shown, illustrating the improved estimation of cloud coverage in our global products.
The second algorithm utilizes date/time information to blend visible and infrared imagery. Weighting functions based on location and time are applied to the IR brightness temperature and visible reflectance to calculate a transparency to combine the blended satellite imagery with a basemap.
Examples of these algorithms can be viewed at the following web locations: