The data sets offered here are based on daily manual visual analysis of satellite data by experienced analysts of the Interactive Multisensor Snow and Ice Mapping System (IMS). By primarily using satellite data of the visible portion of the electromagnetic spectrum maps of the snow cover (on land) and the sea ice cover (over the sea) are generated at 4 km grid resolution. Satellite data used originate from polar orbiting satellites, such as e.g. AVHRR and MODIS, as well as geostationary satellites such as e.g. GOES and METEOSAT. Gaps due to missing daylight and/or cloud coverage are filled by including analyses of the snow cover using passive microwave satellite data; in addition the persistence of the snow cover is taken into account. Over open water the sea ice charts provided by the National Ice Center (NIC) are used in addition. More information about the data set and recently (with version 1.3) also about the data sets and data sources used is given on the IMS Webpage and in this PDF-document.
This data set is unique because it is the only (long-term) data set of the snow cover which is merely based on manual visual analysis of satellite data. As such it is independent from other data sets of the snow cover such as the ESA GlobSnow Schneebedeckung.
Latest data set update at ICDC: June 8, 2017.