3TIER has created a satellite derived dataset composed of more than 10 years of hourly values of Global Horizontal Irradiance (GHI), Direct Normal Irradiance (DNI), and Diffuse Horizontal Irradiance (DIF) at a horizontal resolution of roughly 3 km covering the entire globe. The specific satellites and length of time varies slightly by region due to differences in the availability of data from region to region. See the chart below for more details.

The dataset is based on actual, half-hourly, high-resolution visible satellite imagery observations via the broadband visible wavelength channel at a 2 arc minute resolution. In other words, we provide values in a 2 arc minute by 2 arc minute box surrounding a particular location, and the size of this area changes depending on your latitude. For example, 2 arc minutes of longitude are 3.7 km at the Equator and 2.6 km at 45º N.

Satellite data was originally processed by the University of Wisconsin from the geostationary satellites GOES 8-13. Satellite data was originally processed by the Bureau of Meteorology from the geostationary satellites GOES 9, GMS 5 and the MTSAT satellite operated by the Japan Meteorological Agency. Satellite data was originally processed by EUMETSAT from the geostationary satellites Meteosat 5, 7, and 9.