Hall, D. K., Foster, J. L., Verbyla, D. L. Klein,
A. G. and C. S. Benson. 1998.
Assessment of snow-cover mapping accuracy in a variety
of vegetation-cover densities in central Alaska.
Remote Sensing of Environment. 66:129-137.
Abstract. Field and aircraft measurements were
acquired in April 1995 in central Alaska to map snow cover with MODIS Airborne
Simulator (MAS) data, acquired from high-altitude aircraft. The Earth
Observing System (EOS) Moderate Resolution Imaging Spectroradiometer (MODIS)
is a 36-channel system that will be launched on the EOS-AM-1 platform in
1999. A vegetation-density map derived from integrated reflectances
from MAS data, is compared with an independently produced vegetation type
and density map derived from Thematic Mapper (TM) and ancillary data.
The maps agreed to within 13%, thus corroborating the effectiveness of
using the reflectance technique for mapping vegetation density. Snow
cover was mapped on a 13 April 1995 MAS image, using the original MODIS
prototype algorithm and an enhanced MODIS prototype algorithm. Field
measurements revealed that the area was completely snow-covered.
With the original algorithm, snow was mapped in 96% of the pixels having
<50% vegetation-cover density according to the reflectance map, while
in the areas having >=50% vegetation-cover density, snow was mapped in
only 71% of the pixels. When the enhanced MODIS snow-mapping algorithm
was employed, 99% of the pixels having <50% vegetation-cover density
were mapped as snow, while in the areas having >=50% vegetation-cover density,
snow was mapped in 98% of the pixels. These results demonstrate that
the enhanced algorithm represents a significant improvement over the original
MODIS prototype algorithm, especially in the mapping of snow in dense vegetation.
The enhanced algorithm will thus be adopted as the MODIS at-launch snow-cover
algorithm. Using this simple method for estimating vegetation desnsity
from pixel reflectance, it will be possible to analyze the accuracy of
the MODIS snow-cover algorithm where information on vegetation-cover density
is not available from ground measurements.
Email: D.Verbyla@uaf.edu
Last updated: August 2001