Comparison of Areal Extent of Snow as Determined by AVHRR and SSM/I satellite Imagery
Abstract
Advanced Very High Radiometric (AVHRR) and Special Sensor Microwave Imager (SSM/I) imagery are compared to determine the areal extent of snow. A multi-spectral AVHRR algorithm, utilizing channels 1 (0.63micro m), 2 (0-87 am), 3 (3.7micro m), and 4 (11.0micro m), creates a synthetic image that classified land, snow, water and clouds. The classified images created by this algorithm serve as a baseline for a second algorithm that examines spatially and temporally matched SSM/I imagery. The SSM/I separation algorithm uses the 85 GHz horizontally polarized channel as well as the 37 GHz horizontally and vertically polarized channels. The synthetic image created by this algorithm classifies land, snow and water. Both separation algorithms use empirically derived separation thresholds obtained from bi-spectral scatter plots. Separation is made at a given pixel location based on the radiative identity assigned to that location from various wavelength combinations. The AVHRR data provides high resolution, daytime images of the snow pack but is completely dependent on the absence of clouds to view this ground based feature. The SSM/I data gives lower resolution imagery of the snow during daylight or night time satellite passes and is not affected by the presence of nonprecipitating clouds. A total of 12 sub scenes are analyzed using both data sets and general agreement of the two sets of imagery is established. AVHRR, imagery, satellite, SSM/I, snow.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1992
- Accession Number
- ADA258054
Entities
People
- Robert W. Maxson
Organizations
- Naval Postgraduate School