Summary
About RGBs:
- Generally made from three or more individual or differenced spectral channels; each is assigned to a primary color (red, green, or blue); the final product highlights atmospheric and surface features that are hard to distinguish with single channel images alone
- Provide intuitive, realistic looking products that can reduce ambiguities and simplify interpretation
- In some situations, different features can have the same color or the same feature can appear in different colors. One way to handle this is to animate the products
- Can be overlaid with quantitative information, such as model data or other observational data, enabling more sophisticated analysis and interpretation
- Are increasingly available online and in near real-time
- Future satellite imagers will have increasing numbers of spectral channels, allowing for more RGBs and new applications
Sources of RGBs:
- NASA Rapid Response Gallery: http://earthdata.nasa.gov/data/near-real-time-data/rapid-response
- NRL NexSat Web site: http://www.nrlmry.navy.mil/NEXSAT.html
- NOAA Operational Significant Event Imagery: http://www.osei.noaa.gov/
- CIMSS Satellite Blog: http://cimss.ssec.wisc.edu/goes/blog/
- University of Wisconsin, SSEC: http://ge.ssec.wisc.edu/modis-today/
- NOAA Satellite Information Service: http://www.ssd.noaa.gov/imagery/
- EUMETSAT Real-time Imagery and Image Library: http://www.eumetsat.int/Home/Main/Image_Gallery/index.htm?l=en
- EUMeTrain Web site, provides daily and archived satellite imagery, model output, case studies, and training resources, covering Europe, Middle East, Africa, and North Polar Regions: http://eumetrain.org
The process of building RGBs:
- Step 1: Determine the purpose of the product
- Step 2: Based on experience and available scientific information, select three appropriate channels or channel derivatives that provide useful information
- Step 3: Pre-process the images as needed to ensure that they provide or emphasize the most useful information
- Step 4: Assign the three spectral channels or channel derivatives to the three RGB color components
- Step 5: Review the product for appearance and effectiveness; revise or tune as needed
Colors in the RGB color model:
- Primary colors: Red, green, and blue
- Secondary colors: Yellow (red + green), cyan (green + blue), and magenta (red + blue)
- Gray: Equal amounts of any three colors
- White: The primary colors in equal intensities
- Black: The absence of the primary colors
Uses of RGB products:
Commonly used RGB products:
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