Finland: Sari Metsämäki, a researcher at the Aalto University School of Engineering has developed a new method for remote sensing snow cover in forests. The method uses optical data provided by satellite and takes into account the effect of the forest canopy. Experts believe that the new method gives more accurate results.
Sari Metsämäki has developed a reflectance model. In this model, transmissivity describes the amount of light that is let through by the forest canopy. This value can be determined on the basis of reflectance observations made during full snow cover, with land use maps and field surveying also proving useful in the calculation of transmissivity values. When four factors – reflectance of full snow cover, snow-free ground, forest canopy and the local transmissivity of the forest – are known, the reflectance value measured by a satellite can be used to determine the fractional snow cover. The method works in dense forests too.
The image by the Finnish Environment Institute (SYKE) has been produced using the fractional snow cover mapping method developed by Sari Metsämäki. Grey wedges in the picture represent the edges of satellite images taken from different bands. They will be excluded from calculations because of the biased data they contain.
Source: Aalto University