Design Document for REATMO

REATMO

AUTHOR: Tim Baltzer

Functional Summary:

Apply atmospheric correction to a previously generated composite image.

Background:

A new algorithm for ATMOCOR which includes correction for water vapor has been created. Consequently, there is a need to reprocess composite images using the new ATMOCOR. Since there is data from multiple acquisition days within a composite, a single water vapor image/ ozone image must be created before it is used as input to ATMOCOR. Also, the archived water vapor and ozone images reside in a different projection (Geographic) than the typical composite product (Goodes projection). These as well as other complexities make the need for REATMO necessary.

Comments:

REATMO will be written to apply atmospheric correction to previously computed composite images. Once REATMO has processed all existing composites, it will no longer be a necessary software tool (future composites will have atmospheric correction with water vapor effects already applied).

Requirements:

  • All of the input images must have all the correct projection and datum code fields specified in the DDR.
  • This module is to be designed to process all composites (1KM, US, AL, etc.).
  • Two input ozone images need to be considered (some composites span a month).
  • Up to 20 input water vapor images need to be considered (example: composite spanning Dec 15 - Dec 31).
  • Scope/Limitations:

  • Windowing of the input images is not supported, the entire images must be processed.
  • Overall design:

    Algorithm:

    Inputs to REATMO:
    ------------------
    
  • AVHRR channels 1 and 2 before atmospheric correction applied (in composite space)
  • Scaling method used to store input/output images.
  • Flag to indicate if input image contains radiance or reflectance values.
  • Image containing the date band from the compositing process. This image must be the same size and in the same projection space as the composite.
  • The log file associated with the date band image which specifies the scenes used to generate the composite.
  • The image containing the satellite zenith, solar zenith, and relative azimuth angles (the same size and in the same projection as the composite)
  • image containing elevation (in geographic projection).
  • The base directory in which the water vapor climatology images are stored.
  • The base directory on the silo in which the water vapor acquisition images are stored.
  • The base directory in which the ozone images are stored.
  • The working directory wherein processing should occur.
  • Outputs from REATMO:
    ---------------------
    
  • Output image containing the atmospherically corrected AVHRR channels 1 and 2.
  • The output image containing the resulting normalized difference image computed from the atmospherically corrected AVHRR channels 1 and 2.
  • The quality control output image (in the same size and projection as the composite).
  • Body
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