User's Guide

FIXCAL

Fix the calibration for a NOAA-14 image.

Function:

Fix the calibration for a NOAA-14 image. Since calibration has been improperly applied to some NOAA-14 images, this routine is used to "back-out" the calibration and to re-apply the calibration correctly. The input LAS image is updated by this routine.

Parameters:

IN
Input image. IN may be a single- or multi-band image and may contain BYTE or INTEGER*2 pixel data. Only one band of data may specified, windowing may not be specified.

CHANNEL
Channel number. AVHRR channel number coinciding with the band specified by IN.

Examples:

  1. LAS> fixcal in="ny.dat(:3)" channel=3

    The user has requested to re-apply calibration to the third band of LAS image "NY.DAT". This band of data is from the AVHRR channel 3. Only band 3 will be updated.

Description/Algorithm:

A line of the specified input band is read. For each sample, the improperly applied calibration is accounted for, and calibration is applied correctly. The line of data is then updated in the input image. Processing continues until each line of the input band has been updated.

Nonfatal Error Message:

  1. [fixcal-warn] Nonfatal error encountered

    A nonfatal error was encountered during processing. The image data is probably valid and therefore saved. The error message that is displayed immediately preceding this message is the specific error that was encountered. Processing continues.

Fatal Error Messages:

  1. [fixcal-fatal] Fatal error encountered

    A fatal error was encountered during processing. Processing is terminated. The error message that is displayed immediately preceding this message is the specific error that was encountered.

User Notes:

  1. FIXCAL is necessary because for some time NOAA-14 scenes were being calibrated with nonlinear correction being applied to temperature values instead of energy values. For this reason, existing images with the improper calibration applied must corrected by running FIXCAL. HRPTCAL has been modified so that calibration is properly applied in the future.

  2. Subsampling an image (except for bands) is not allowed. Only one (1) band may be specified.

  3. FIXCAL rounds it's newly computed values.

  4. If the data type of the image is byte, it is assumed that US processing and scaling is to be applied. If the data type of the image is I*2, it is assumed that Global 1KM processing and scaling is to be applied. All other data types are invalid.