ISIS Application Documentation

lrowacphomap

Apply Hapke bidirectional reflectance model photometric correction to multiband cubes

Overview

Parameters

Description

lrowacphomap implements photometric correction based on the full form of bidirectional reflectance model by Hapke (2012). See below for full description of the model. It takes an input cube to be corrected, an output cube to write the results to, a parameter cube that defines the Hapke parameters to be used for the correction, a PVL input file to define the algorithm and an optional backplane cube. Here's an example command line:

  lrowacphomap from=input.cub+1 to=output.cub phoalgo=hapke.pvl phoparcube=params.cub backplane=input.cub+2,3,4,5,6

The input cube (from) must have a BandBin label.

  Example (containing image and backplane bands):

  Group = BandBin
    FilterNumber = (1, 2, 3, 4, 5, 6)
    Center       = (321, 321, 321, 321, 321, 321)
    Width        = (32, 32, 32, 32, 32, 32)
    Name         = (Image, Phase, Emission, Incidence, lat, lon)
  End_Group

The PVL file (phoalgo) contains the algorithm name, reference values for normalization, and a Parameters group to define the parameter bands from the parameter cube to use.

  Example:

  Object = PhotometricModel 
    Name   = HapkeLROC
    Units  = Degrees
    Incref = 60.0
    Emiref = 0.0
    Pharef = 60.0
    
    Group = Parameters
      BandBinCenter = 321
      Bands = (1, 2, 3, 4, 5, 6, 7, 8, 9)
    EndGroup
  EndObject

The Incref, Emiref and Pharef are the incidence, emission and phase angles to be used as the common illumination and viewing angles. It will be used to normalize the photometric correction parameter to these angles. The equation used to create the photometrically corrected I/F is:

          n_IOF = IOF / Model(g,e,i) * Model(Pharef,Emiref,Incref)

          where Model(g,e,i) is the model value for phase (g), emission (e), and incidence (i) at each pixel,
          Model(Pharef,Emiref,Incref) is the model value at the given common geometric angles.

The parameter cube (phoparcube) should be a 9 band cube with the parameters in the order:

backplane cube must contain 5 bands (in order): Phase Angle, Emission Angle, Incidence Angle, Latitude, Longitude

Hapke Bidirectional Reflectance Model

In full form of bidirectional reflectance model by Hapke (2012), the radiance factor I/F is

I is radiance, F is perfectly diffuse surface illuminated at i = e = g = 0 (corresponds to the flat-field).

The bidirectional reflectance r(i,e,g) is

where i is incidence angle, e is emission angle, and g is phase angle, i_e and e_e are the effective angle of incidence and emission respectively.

Then, K is (porosity effect)

p(g) is, (H-G phase function)

B_S(g) is, (Shadow Hiding Opposition surge Effect: SHOE )

M(i,e) is, (Isotropic Multiple Scattering Approximation: IMSA)

where H(x) is,

where r₀ is,

B_C(g) is, (Coherent Backscatter Opposition surge Effect: CBOE)

Then, S(i,e,g) is, (Shadow effect)

When i e,

where and are,

When e i,

where and are,

where is,

and is, (y corresponds to i or e)

where E₁ and E₂ are, (y corresponds to i or e)

is given by,

Thus it can be written as,

Finally, free parameters are,

      w (Single scattering albedo)
      b (H-G phase function asymmetry)
      c (H-G phase function amplitude)
      B_C0 (CBOE amplitude)
      h_C (CBOE angular width)
      B_S0 (SHOE amplitude)
      h_S (SHOE angular width)
       (Roughness parameter)
       (Filling factor)

Reference:

      Hapke, B. (2012) Theory of Reflectance and Emittance Spectroscopy, Cambridge Univ. Press.

History

Kris Becker	2010-02-21	Original version.
Dan Clarke	2012-09-28	Added full Hapke model. Optimized processing. Updated documentation.
Adam Licht	2013-01-18	Fixed an error in how parameters were loaded for use in the refrence model calculation.
Cordell Michaud	2022-05-10	Refactored lrowacphomap for testability and added functional tests.
Cordell Michaud	2024-04-02	Added new default for PHOALGO. Added new default for PHOPARCUBE.

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File Modified: 02/21/2025 19:28:12

Parameter Groups

Files

Name	Description
FROM	Input cube
TO	Output cube
BACKPLANE	Backplane Cube
PHOALGO	Pvl file
PHOPARCUBE	Parameter cube

Photometry

Name	Description
MINPHASE	Minimum phase angle to trim
MAXPHASE	Maximum phase angle to trim
MINEMISSION	Minimum emission angle to trim
MAXEMISSION	Maximum emission angle to trim
MININCIDENCE	Minimum incidence angle to trim
MAXINCIDENCE	Maximum incidence angle to trim

Other Options

Name	Description
USEDEM	Use DEM instead of ellipsoid for photometric angle calculations
PHOTOMETRYONLY	Output only photometry value in output cube.
NORMALIZED	Normalize photometry value before applying to input image.

Files: FROM

Description

Use this parameter to select the input filename.

Type	cube
File Mode	input
Filter	*.cub

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Files: TO

Description

This file will contain the photometrically corrected image data after being corrected.

Type	cube
File Mode	output
Pixel Type	real

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Files: BACKPLANE

Description

This file will contain the backplane data. It must have "Phase Angle", "Emission Angle", "Incidence Angle", "Latitude" and "Longitude".

Type	cube
File Mode	input
Pixel Type	real
Internal Default	Calculate the photometry on the fly

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Files: PHOALGO

Description

This file will contain the photometric correction algorithm information. Here's an example pvl file for Hapke photometric correction:

    Object = PhotometricModel 
      Name   = HapkeLROC
      Units  = Degrees
      Incref = 60.0
      Emiref = 0.0
      Pharef = 60.0
      
      Group = Parameters
        BandBinCenter = 321
        Bands = (1, 2, 3, 4, 5, 6, 7, 8, 9)
      EndGroup
    EndObject

Type	filename
File Mode	input
Default Path	$lro/calibration
Default	$lro/calibration/WAC_hapke_full.????.pvl
Filter	*.pvl

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Files: PHOPARCUBE

Description

This file will contain the parameters (in order) Wh, Hg1, Hg2, Bc0, hc, B0, Hh, Theta, phi. See the main program documentation for a full description.

Type	cube
File Mode	input
Default	$lro/calibration/WAC_global_7bands_1x1_wbhs70NS_const_each_pole.????.cub
Filter	*.cub

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Photometry: MINPHASE

Description

Pixels which have a phase angle less than this value will be trimmed.

Type	double
Default	0.0
Minimum	0.0 (inclusive)
Maximum	180.0 (inclusive)
Less Than or Equal	MAXPHASE

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Photometry: MAXPHASE

Description

Pixels which have a phase angle greater than this value will be trimmed.

Type	double
Default	180.0
Minimum	0.0 (inclusive)
Maximum	180.0 (inclusive)
Greater Than or Equal	MINPHASE

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Photometry: MINEMISSION

Description

Pixels which have an emission angle less than this value will be trimmed.

Type	double
Default	0.0
Minimum	0.0 (inclusive)
Maximum	90.0 (inclusive)
Less Than or Equal	MAXEMISSION

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Photometry: MAXEMISSION

Description

Pixels which have a emission angle greater than this value will be trimmed.

Type	double
Default	90.0
Minimum	0.0 (inclusive)
Maximum	90.0 (inclusive)
Greater Than or Equal	MINEMISSION

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Photometry: MININCIDENCE

Description

Pixels which have an incidence angle less than this value will be trimmed.

Type	double
Default	0.0
Minimum	0.0 (inclusive)
Maximum	180.0 (inclusive)
Less Than or Equal	MAXINCIDENCE

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Photometry: MAXINCIDENCE

Description

Pixels which have a incidence angle greater than this value will be trimmed.

Type	double
Default	90.0
Minimum	0.0 (inclusive)
Maximum	180.0 (inclusive)
Greater Than or Equal	MININCIDENCE

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Other Options: USEDEM

Description

Phase, Emission, and Incidence angles can be calculated from the elipsoid (default) or from the DEM. The difference is that using the DEM the surface roughness is taken into account.

Type	boolean
Default	False

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Other Options: PHOTOMETRYONLY

Description

Only the photometry value will be written to the output cube, not the original image data. Used for testing photometry calculation.

Type	boolean
Default	False

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Other Options: NORMALIZED

Description

Set to False to cause the photometry value to not be normalized. Used for testing photometry calculation.

Type	boolean
Default	True

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Quick Links

Documentation Versions

lrowacphomap

Description

Hapke Bidirectional Reflectance Model

Categories

History

Parameter Groups

Files

Photometry

Other Options

Files: FROM

Description

Files: TO

Description

Files: BACKPLANE

Description

Files: PHOALGO

Description

Files: PHOPARCUBE

Description

Photometry: MINPHASE

Description

Photometry: MAXPHASE

Description

Photometry: MINEMISSION

Description

Photometry: MAXEMISSION

Description

Photometry: MININCIDENCE

Description

Photometry: MAXINCIDENCE

Description

Other Options: USEDEM

Description

Other Options: PHOTOMETRYONLY

Description

Other Options: NORMALIZED

Description