A freeware-based multispectral data analysis tool kit for satellite data has been developed to assist research and development of remote-sensing applications as well as education and training of remote-sensing scientists; it is called HYDRA—HYper-spectral data viewer for Development of Research Applications. HYDRA provides a fast and flexible interface that allows users to explore and visualize relationships between radiances (or reflectances and brightness temperatures) and wavelength (or wavenumber) using spectra diagrams, cross sections, scatter plots, multichannel combinations, and color enhancements on a pixel-by-pixel basis with full access to the underlying metadata of location and time.
HYDRA enables interrogation of multispectral (and hyperspectral) fields of data so that a) pixel location and spectral measurement values can be easily displayed; b) spectral channels can be combined in linear functions and the resulting images displayed; c) false color images can be constructed from multiple channel combinations; d) scatter plots of spectral channel combinations can be viewed; e) pixels in images can be found in scatter plots, and vice versa; f) transects of measurements can be displayed; and g) soundings of temperature and moisture as well as spectra from selected pixels can be compared.
The World Meteorological Organization has added HYDRA to its Virtual Laboratory for Satellite Training and Data Utilization to enable research with satellite data and to enhance training capabilities. The Virtual Laboratory is designed to provide the instructors and students with a set of easy-to-use tools for creating and conducting training sessions. HYDRA is now part of this international tool kit.
This paper describes some of the procedures for displaying multispectral data using HYDRA and presents some examples with Moderate Resolution Imaging Spectroradiometer (MODIS) and Atmospheric Infrared Sounder (AIRS) data.
Cooperative Institute for Meteorological Satellite Studies, Madison, Wisconsin
NOAA Satellite and Information Services/ORA, Madison, Wisconsin