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ISIS Documentation

lrowacphomap

Apply Hapke bidirectional reflectance model photometric correction to multiband cubes

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, ie and ee are the effective angle of incidence and emission respectively.

Then, K is (porosity effect)

   

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

   

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

   

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

   

where H(x) is,

   

where r0 is,

   

BC(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,

   

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)
      BC0 (CBOE amplitude)
      hC (CBOE angular width)
      BS0 (SHOE amplitude)
      hS (SHOE angular width)
       (Roughness parameter)
       (Filling factor)
    

Reference:

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


Categories


History

Kris Becker2010-02-21 Original version.
Dan Clarke2012-09-28 Added full Hapke model. Optimized processing. Updated documentation.
Adam Licht2013-01-18 Fixed an error in how parameters were loaded for use in the refrence model calculation.
Cordell Michaud2022-05-10 Refactored lrowacphomap for testability and added functional tests.
Cordell Michaud2024-04-02 Added new default for PHOALGO. Added new default for PHOPARCUBE.

Parameters

Files

Use this parameter to select the input filename.
Type cube
File Mode input
Filter *.cub

This file will contain the photometrically corrected image data after being corrected.
Type cube
File Mode output
Pixel Type real

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

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

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

Photometry

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

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

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

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

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

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

Other Options

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

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

Set to False to cause the photometry value to not be normalized. Used for testing photometry calculation.
Type boolean
Default True