photompr Documentation

photompr - Photometric Correction Parameters
Create the solar correction data file (TFILE) for PHOTOM to
photometrically correct a cube.  PHOTOMPR does not perform the
actual correction of the input cube, PHOTOM must be run using
the TFILE created by this program.  The TFILE consists of
multiplicative and additive values that will be applied to the
brightness values of the input cube in PHOTOM (DN * A + B).
There are several functions that can be chosen from to apply to
the cube.  For detail on the individual functions see the
documention of the parameter FUNC below.

There is also the option to "build your own function".
The main program supplies the subroutine USR with the following
from which the user can build a photometric function:
		INC    = Incidence angle in degrees
                EMA    = Emission angle in degrees
                PHASE  = Phase angle in degrees
	        MUNOT  = Cosd(incidence angle)
                   MU  = Cosd(emission angle)
                ALPHA  = Cosd(phase angle)
	          LAT  = Latitude
                  LON  = Longitude
	        C(1-9) = Up to nine REAL*4 user-defined working
			 variables.  When the program is
                         executed, the values of C(1-9) will be
                         printed out with their labels (below) for
                         user reference.  (Values are entered by the
                         user when this program is tutored in TAE)
    *NOTE: All angles are in degrees NOT radians.

The main program then expects the following:
              LABEL(9) = The user should supply a corresponding label or
                         definition of each working variable used -
                         for print out and user reference purposes.
             REAL*4 A  = The function of the user MUST return a
                         multiplicative value to be applied to the
                         individual brightness values of the input
                         cube.
             REAL*4 B  = The function of the user MUST return a
                         additive value to be applied to the
                         individual brightness values of the input
                         cube.

The user PDF must look exactly like the PDF of PHOTOMPR, except the
parameter FUNC must be the default value of (4) which will cause the
main program to execute the subroutine USR.  There is probably no
reason for the user to change anything else in the PDF.

To run the USR version, all the user needs to do is tutor the user-
supplied filename instead of PHOTOMPR.
          Example:  T MYPHOTO
Everything will look the same except now PHOTOMPR will execute the
USR routine.  At this point, the user may use the parameter C(1-9)
to enter up to nine values for the working variables used and labeled
in the USR subroutine.

PROGRAMMER: Jim Mathews

Input cube file name

NONE

Input subcube specifier

--

Output TFILE name to be passed
to photom

sun.dat

Use backplane values for inc,
ema and phase angles (YES,NO)

NO

Incidence angle boundary

89.0

Emission angle boundary

89.0

Photometric functions:
LUNLAM Lunar-Lambert function
LAMB   Lambert function with
        isotropic atmosphere
        properties
MIN    Minnaert function
HAPHEN Hapke - Henyey-Greenstein
HAPLEG Hapke - Legendre
TRIM   Trim only
MOONPR Normalized albedo for
	the moon
USER   User function

Use the following parameters
   for Lunar-Lambert function

LUNLAM

Lunar-Lambert coefficient

1.0

Incidence angle normalization

Use the following parameters
   for Lambert function

0.0

Single scattering albedo

0.8

Optical depth

0.3

Spherical shell thickness/
   radius of planet

Use the following parameter
   for Minnaert function

.003

Minnaert coefficient

Use the following parmeters
  both Hapke functions

1.0

Single-scattering albedo

0.

Compaction parameter

0.

Opposition surge amplitude

0.

Average slope of surface

Use the following parameters
  for Hapke-Henyey function only

0.

Asymmetry factor

0.

Second asymmetry factor

Use the following parameters
   for Hapke-legendre func only

0.

First coefficient

0.

Second coefficient

Use the following parameters
   for the Trim function

0.

Amount to trim (degrees)

180.

Latitude of center of trim

0.

Longitude of center of trim

Use the following parameters
   for the Moonpr function

0.

First coefficient

-0.019

Second coefficient

0.000242

Third coefficient

Use the following parameter
   for user function

-.00000146

Values for usr subroutine
  working variables

--

ADDITIONAL NOTES:

Parm	Description
FROM	Filename of input cube. The input cube can be in any map projection. 8 or 16 bit data.
SFROM	SFROM specifies the subcube using a single string for all three dimensions of the cube. The order of the three dimensions is always "samples:lines:bands". If a dimension is left blank, all the data for that dimension is selected. The default value of NULL for SFROM selects the entire cube. Any application below can be used for any dimension. To select specific data from any dimension: "10-100(3):11,12,15-20:1-10(2)" = This example will select every third sample starting with sample 10 thru 100. It selects lines 11 and 12, and 15-20. It selects every other band, starting with band 1 thru 10. There are special characters that can be used for selecting a subcube efficiently, such as "*","#", and "~". For examples type "help sfrom" in TAE. **NOTE** For more examples and explanation of the many features of the SFROM parameter, tutor the sfrom.pdf or refer to Introduction To ISIS, Section 6, of the ISIS User's Manual **
TFILE	The output file name of the solar correction file that will be applied to the input cube in PHOTOM. The file contains multiplicative and additive values that will be applied to the individual brightness values of the input cube.
BACK	If BACK=YES, the backplane values of incidence, phase and emission angles will be used to calculate the photometric function. Otherwise, the values will be calculated within the program. NOTE: If BACK=YES, all 3 angles must be in the backplanes. Use "geoback" to put angles in backplanes.
INC	INC is used as an incidence angle boundary. For any pixel point of the input cube that is greater than INC it is set to zero, "cut-off". This effects the terminator of the planet in the cube. The value should not be set above 90 degrees.
EMA	EMA is used as an emission angle boundary. For any pixel point of the input cube that is greater than EMA it is set to zero, "cut-off". This effects the limb of the planet in the cube. The value should not be set above 90 degrees.
FUNC	LUNAR-LAMBERT Function: NORMAL ALBEDO = BRIGHTNESS/f(phase)/ [2*L*COS(INC)/(COS(INC)+COS(EMA))+(1-L)*COS(INC)] Where: L=Lunar-Lambert coefficient LAMBERT Function with isotropic atmosphere elements: Assumptions - isotropic scattering - single scattering - 60 degree approximate for down-welling radiation - Lambertian surface HNORM = Ratio of thickness of spherical shell to radius of planet W0 = Single scattering albedo TAU = Optical depth GAMMA = ratio of the thickness of the shell to the slant path length fro a particular incidence angle HNORM/(SQRT(1+HNORM)**2 - SIN(INC)**2) - COS(INC)) M = 1.0/COS(EMA) + 1.0/GAMMA IS = (W0/4)*(GAMMA/(GAMMA-.5))*(EXP(-TAU/GAMMA)-EXP(-2*TAU)) ALBEDO = BRIGHTNESS - (W0/4)*(GAMMA/(COS(EMA)+GAMMA))*(1-EXP(-TAU*M)) ____________________________________________________________ EXP(-TAU/COS(EMA))*[GAMMA*EXP(-TAU/GAMMA) + IS] MINNAERT Function: ALBEDO = BRIGHTNESS * [COS(EMA)/(COS(EMA)*COS(INC))**K] TRIM function can be used to simply trim the image some angular amount (TRIMANG) from a given central point (CLAT,CLON). This function can also be used to just trim relative to emission angle or incidence angle by leaving TRIMANG at the default of 180 degrees. MOONPR function can be used to compute the normalized albedo for the Moon.
L	Lunar-Lambert coefficient varies from 0.0 to 1.0. Used in in the Lunar-Lambert function(1).
W0	Single scattering albedo. One of the isotropic atmosphere properties used in the Lambert equation.
TAU	Optical depth. One of the isotropic atmosphere properties used in the Lambert equation.
HNORM	The ratio of the spherical shell thickness to the radius of the planet. One of the isotropic atmosphere properties used in the Lambert equation.
W	Single-scattering albedo of an average particle. Enter average value of W for planet or terrain of interest. Valid values 0.0 to 1.0
H	Compaction parameter of backscatter function. Only important at low phase angles.
B0	Opposition surge amplitude prameter. Only important at low phase angles.
THETA	Average topographic slope angle of surface roughness at subresolution scales. Typical values 0.0 to 40.0 degrees.
HG1	Asymmetry factor of the Henyey-Greenstein particle phase function. Valid values -1.0 to 1.0.
HG2	Second asymmetry factor for 2-lobed Henyey-Greenstein particle phase function. (Default to 0.0 for single-lobe model.) See Domingue et al., Icarus 90, p. 30-42.
BL	First coefficient of Legendre Polynomial. P(alpha) = 1.0 +BL*cos(alpha)+CL*(1.5*cos(alpha)**2-.5)
CL	Second coefficient of Legendre Polynomial. P(alpha) = 1.0 +BL*cos(alpha)+CL*(1.5*cos(alpha)**2-.5)
M1	First coefficient of the Moonpr polynomial. 1. + M1 * phase + M2 * phase**2 + M3 * phase**3
M2	Second coefficient of the Moonpr polynomial. 1. + M1 * phase + M2 * phase**2 + M3 * phase**3
M3	Third coefficient of the Moonpr polynomial. 1. + M1 * phase + M2 * phase**2 + M3 * phase**3 Build your own routine - read documentation for PHOTOMPR.
K	The coefficient used in the Minnaert equation. Usually < 1.0
C	C allows the user to enter up to nine real values that will be passed to the USR subroutine as working variables. Within the USR subroutine, the user must remember to "label" each value of C accordingly for later reference in the printer output. Also note that the values of C can change or be used as constants in the USR subroutine.