Three sources of satellite data are used in the creation of winter snow cover maps:
1.NOAA AVHRR images from the Dundee Satellite Station
With two operational satellites, AVHRR
to date remains the principal tool used in the creation of snow maps. Depending
on
the satellites orbit and the lighting conditions between 1 and 4 images
are available each day thus maximizing the opportunities for exploiting
cloud free windows.
Two methods are used to classify the AVHRR snow cover:
Method A: ISODATE spectral clustering with clouds masking and NDVI thresholds.
Method B: AVHRR-SM integrated spectral clustering and threshold filtering.
Link to sample AVHRR/2 false colour image and snow map.
2. ATSR 2 (Along Track Scanning Radiometer).
The ATSR/ 2 is an optical to thermal scanner attached to ERS/2. Although it passes over Scotland on
average only once a week it has an excellent range of imaging channels that enable very positive snow to
cloud discrimination. ATSR/2 data is accessed via the Tromso Satellite Recieving Station .
Method applied to map snow using ATSR/2: NDSI and NDVI thresholding with cloud/shadow masking.
Link to sample ATSR/2 false colour image and snow map.
3. MODIS (Moderate Resolution Imaging Spectrometer).
MODIS an instrument on the EOS AM /Terra mission provides the potential for significant advances in snow cover mapping with its
combination of 250 - 500 m spatial resolution and imaging channels that enable positive snow - cloud discrimination. Data from this
sensor will be received directly from the Dundee satellite station and potentially introduces a next generation in improved Scottish snow mapping.
Method applied to map snow using MODIS:
Method A: NDSI and NDVI thresholds and cloud/shadow masks
Method B: Integrated threshold and multi-scale and Matched filter pixel un-mixing.
Link to sample MODIS false colour image and snow map.
LINKS TO ASSOCIATED SCOTTISH SNOW COVER PAGES:
1.
Intresting images collected by the Dundee University Remote Sensing
Group .