Help for TCAL2

PURPOSE:

   TCAL2 is a program which calibrates data to ground radiance, ground
 temperature, or emittance for thermal images (defined by what???)
 by calling lowtran. The input is data which have already been calibrated
 to instrument radiance (expected in in watts/...) (for TIMS data this is
 done with the program TIMSCAL).  The output is a band interleaved by line
 (BIL) data set of all the bands in two byte integer. TCAL2 is different from
 TIMSCAL2 in that it is not only for TIMS images (i.e. it can run on different
 sized images and has an option for filter function input), it can take as
 a digital elevation model (DEM) file as an input to account for varying
 elevation across a scene and it can read in atmospheric data to pass to the
 Lowtran7.

EXECUTION:

   The following is the execution statement format for TCAL2:

	TCAL2 INP = pix OUT = calpix PARAMS

   where INP, OUT, and PARAMS are parameters discussed in their res-
 pective parameter sections. 


OPERATION:

   TCAL2 takes as input any thermal dataset that is calibrated instrument
 radiance in watts (for TIMS this is the output dataset of TIMSCAL in IRAD
 mode, WATTS units). An input DEM can also be specified; if one is, it will
 be used to obtain the correct target elevations for input into Lowtran. Tcal2
 uses LOWTRAN7 to compute the atmospheric path radiance, transmittance, and
 ground reflected atmospheric radiance. These values are convolved with the
 instrument functions and the instrument perceived radiances to obtain either
 ground radiance, ground temperature or emittance. The formula used to compute
 ground radiance is:

        IRAD  =  [GRAD + (1.0-e)*L   ]*Trans + L
                                sky           path

 To compute emittance, one channel is assumed to have a constant (user
 specified) emittance. The temperature of each pixel is computed, based upon
 this assupmtion. For this temperature, the blackbody radiance in each bandpass
 is computed. The emittance is the ratio of the computed ground radiance to the
 blackbody radiance of that band.
   The units output for radiance images are in milliwatts/m**2/um/sr. The units
 output for temperature images are in hundredths of degrees Celsius. Units 
 output for emissivity are dimensionless, but scaled by 10,000. Output is in 
 halfword (two byte signed integer) format. 


WRITTEN BY:  J. H. REIMER    1982

COGNIZANT PROGRAMMER:  Ron Alley

REVISION: 3,  June 15, 1992

history:
    mj-n translate to c and genaralize to work on non-tims images