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Viewable Snow Covered Area Validation Masks over Rugged and Forested Terrain

posted on 16.09.2020 by Stillinger, Timbo, Bair, Ned

These data are maps of viewable snow cover generated from panchromatically sharpened cloud-free WorldView-2 and -3 data within 2 days of a Landsat 8 OLI acquisition or near-nadir MODIS acquisition. The spatial resolution of these validation data ranges from 0.34 m to 0.55 m, depending on the view angle of WorldView. ValKey.csv shows the list of validation dates and the corresponding Landsat 8 OLI and MODIS imagery.  Validation images from December to June were selected to account for variability in illumination conditions, snow cover, and snow albedo. The imagery spans diverse locations across California’s Sierra Nevada that represent the heavily forested western slope, higher elevation regions, and drier eastern slopes. The WorldView images range from well illuminated alpine scenes above the tree line in June to heavily shadowed scenes below the tree line in December. The snow-covered WorldView pixels are assumed to be pure endmembers of 100% snow, which are then coarsened to Landsat or MODIS spatial resolutions and provided here as geotiffs. Neither WorldView, Landsat, nor MODIS can see through thick tree canopies, so the data is comprised of snow that an optical sensor identifies. Complete methods used to generate the dataset are available in the companion publication: tbd

Binary snow cover maps at the native worldview resolution are unsigned 8 bit integers with fill pixels set to zero, snow pixels set to one, and snow free pixels set to two.

Fill Pixels [0]

Snow Covered Pixels [1]

Snow Free Pixels [2]

Fractional snow covered area geotiffs in the projections and at the spatial resolution of Landsat 8 and MODIS products are signed 16-bit integers with a fill value of  -32768. The divisor and offset are 1000 & 0 respectively.

Fractional snow covered area [0-1000)]  (divisor of 1000 and offset of 0 for measurement range of 0-1)

Fill Pixels  [-32768]