ISIS Application Documentation
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Perform photometric corrections on a cube
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This program performs photometric correction on image pixels acquired under different illumination and viewing geometries by adjusting the brightness and contrast such that the resulting image appears as if obtained under uniform conditions. The photometric correction is applied to each pixel by computing a photometric model based on local photometric angles and a set of parameters that defines the model. Currently, no default values are assigned for any parameter names in the ISIS version of photomet.
Photometric angles can be computed from the following:
The user must select a photometric model and a normalization model, with the option of adding an atmospheric model. Each of these models has a set of parameters that specifies its operation, which the user must provide. The different models can be mixed and matched to produce variations of the photometric correction.
There are three aspects of a photometric correction that should be considered when running the photomet program:
The intent of topographic normalization is to correct for the variation in incidence, emission, and phase angles within and between images. Topographic normalization involves both a multiplicative correction that adjusts the contrast for a unit slope to reference conditions, and an additive correction to keep the average brightness uniform.
In practice, the albedo may be nonuniform, so a multistep process is used:
The normalization models that use an atmospheric correction are albedoatm, shadeatm,
and topoatm. If using the GUI interface photomet will automatically exclude
all atmospheric models for normaliztion types that do not require an atmospheric
correction.
Question: What happens if the normalization model I chose does not perform
an atmospheric correction although I have an atmospheric model defined in my PVL
file?
Answer: If you have chosen a normalization model that does not
perform atmospheric correction, then the image is normalized without applying
the atmospheric correction.
New Developments
A new parameter name "chngpar" was added to photomet to allow the user to enter a string consisting of parameter names and values outside of the PVL files. This string replaces any parameter already defined. This is useful when one or two parameter values change for each image but all the other parameter values remain the same.
The parameter name "ZEROB0STANDARD" was shortened to "ZEROB0ST," but the longer name will still work for backward compatibility. The default is to get the user setting for "ZEROB0ST" from the PVL file. If no PVL file exists and the user does not specify a "FALSE" or "TRUE" option, the program will automatically default to "TRUE" to follow the default setting in previous photomet versions. PLEASE NOTE: This change was actually not added because the ability to support aliases (or deprecated) values has not been fully implemented in ISIS. As a result, you must use the full ZEROB0STANDARD parameter name.
The parameter name "INCMAT" is no longer required when the "ALBEDO" normalization model is selected. The parameter name will still appear in the GUI for backward compatibility, but does not need to be defined by the user in the GUI or on the command line.
A set of photomet PVL templates for Mars and other planetary bodies developed in ISIS2 are now available in $ISISROOT/appdata/templates/photometry/ directory. There are also additional examples of PVL files for different photometric models under "Example PVL files," later in this document.
Note: The NoNormalization model has been removed because it duplicated the functionality of the shade model. Use shade with incref=0 and albedo=1.0 instead.
The program photemplate can be used to set up the PVL file containing the selected options for photomet.
The tables below show the models and their related parameter requirements along with the ISIS2 default values. The ISIS2 default values are only meant to serve as possible initial values to test backward compatibility since there are no default values defined in ISIS.
Name | Required parameter names |
---|---|
Hapkehen | B0, hg1, hg2, hh, theta, wh |
Hapkeleg | Theta, wh, bh, ch, hh, b0, zerob0st |
Lambert | None |
LommelSeeliger | None |
LunarLambert | L |
LunarLambertEmpirical | Phaselist, llist, phasecurvelist |
LunarLambertMcEwen | None |
Minnaert | K |
MinnaertEmpirical | Phaselist, klist, phasecurvelist |
Name | Description | ISIS2 default | Valid range |
---|---|---|---|
B0 | Hapke opposition surge component | 0.0 | 0 <= value |
Bh | Hapke Legendre coefficient for single particle phase function | 0.0 | -1 <= value <= 1 |
Ch | Hapke Legendre coefficient for single particle phase function | 0.0 | -1 <= value <= 1 |
Hg1 | Hapke Henyey Greenstein coefficient for single particle phase function | 0.0 | 0 <= value <= 1 |
Hg2 | Hapke Henyey Greenstein coefficient for single particle phase function | 0.0 | 0 <= value <= 1 |
Hh | Hapke opposition surge component | 0.0 | 0 <= value |
K | Minnaert function exponent | 1.0 | 0 <= value |
L | Lunar-Lambert function weight | 1.0 | No limit |
Theta | Hapke macroscopic roughness component | 0.0 | 0 <= value <= 90 |
Wh | Hapke single scattering albedo component | 0.5 | 0 < value <= 1 |
Zerob0st | Flag to set opposition surge B0 to zero | True | True or False |
Phaselist | Phase list for empirical functions | None | String |
Llist | Exponent list of limb darkening values | None | String |
Klist | Exponent list of limb darkening values | None | String |
Phasecurvelist | Phase curve list of brightness values | None | String |
The functions are defined as follows, where phase is the phase angle, and u0 and u are the cosines of the incidence and emission angles, respectively:
Function model name | Required parameters |
---|---|
Anisotropic1 | Bha, hnorm, nulneg, tau, tauref, wha |
Anisotropic2 | Bha, hnorm, nulneg, tau, tauref, wha |
HapkeAtm1 | Hga, hnorm, nulneg, tau, tauref, wha |
HapkeAtm2 | Hga, hnorm, nulneg, tau, tauref, wha |
Isotropic1 | Hnorm, nulneg, tau, tauref, wha |
Isotropic2 | Hnorm, nulneg, tau, tauref, wha |
Name | Description | ISIS2 Default | Valid Range |
---|---|---|---|
Bha | Coefficient of the single particle Legendre phase function | 0.85 | -1 <= value <= 1 |
Hga | Coefficient of single particle Henyey Greenstein phase function | 0.68 | -1 < value < 1 |
Hnorm | Atmospheric shell thickness normalized to the planet radius | 0.003 | 0 <= value |
Nulneg | Specifies if negative values after removal of atmospheric effects will be set to NULL | NO | YES or NO |
Tau | Normal optical depth of the atmosphere | 0.28 | 0 <= value |
Tauref | Reference value of tau to which the image will be normalized | 0.0 | 0 <= value |
Wha | Single scattering albedo of atmospheric particles | 0.95 | 0 < value < 1 |
Function name | Normalization function type | Required parameter names |
---|---|---|
Albedo | Albedo contrasts uniform | Albedo, incref, thresh |
AlbedoAtm | Albedo with atmosphere | Incref |
Mixed | Albedo at low incidence blended to topo at high incidence | Albedo, incmat, incref, thresh |
MoonAlbedo | Special Lunar model | Bsh1, d, e, f, g2, h, wl, xb1, xb2, xmul |
Shade | Shaded relief model | Albedo, incref |
ShadeAtm | Shaded relief with atmosphere | Albedo, incref |
Topo | Topographic shading uniform | Albedo, incref, thresh |
TopoAtm | Topographic shading with atmosphere | Albedo, incref |
Name | Description | ISIS2 default | Valid range |
---|---|---|---|
Albedo | Albedo to which the image will be normalized | 1.0 | No limit |
Bsh1 | Albedo dependent phase function normalization parameter | 0.08 | 0 <= value |
D | Albedo dependent phase function normalization parameter | 0.14 | No limit |
E | Albedo dependent phase function normalization parameter | -0.4179 | No limit |
F | Albedo dependent phase function normalization parameter | 0.55 | No limit |
G2 | Albedo dependent phase function normalization parameter | 0.02 | No limit |
H | Albedo dependent phase function normalization parameter | 0.048 | No limit |
Incmat | Specifies incidence angle where albedo normalization transitions to incidence normalization | 0.0 | 0 <= value < 90 |
Incref | Reference incidence angle to which the image will be normalized | 0.0 | 0 <= value < 90 |
Thresh | Sets upper limit on amount of amplification in regions of small incidence angle | 30.0 | No limit |
Wl | Wavelength in micrometers of the image being normalized | 1.0 | No limit |
Xb1 | Albedo dependent phase function normalization parameter | -0.0817 | No limit |
Xb2 | Albedo dependent phase function normalization parameter | 0.0081 | No limit |
Xmul | Used to convert radiance to reflectance or apply a calibration fudge factor | 1.0 | No limit |
Example 1: Object = PhotometricModel Group = Algorithm PhtName = Lambert EndGroup EndObject Object = NormalizationModel Group = Algorithm NormName = Shade Incref = 0.0 Albedo = 1.0 EndGroup EndObject -------------------------------- Example 2: Object = PhotometricModel Group = Algorithm PhtName = Minnaert K = 0.5 EndGroup EndObject Object = NormalizationModel Group = Algorithm NormName = Albedo Incref = 0.0 Incmat = 0.0 Albedo = 1.0 Thresh = 30.0 EndGroup EndObject -------------------------------- Example 3: Object = PhotometricModel Group = Algorithm PhtName = Hapkehen Wh = 0.52 Hh = 0.0 B0 = 0.0 Theta = 30.0 Hg1 = 0.213 Hg2 = 1.0 EndGroup EndObject Object = AtmosphericModel Group = Algorithm AtmName = hapkeatm2 Hnorm = 0.003 Tau = 0.28 Tauref = 0.0 Wha = 0.95 Hga = 0.68 EndGroup EndObject Object = NormalizationModel Group = Algorithm NormName = albedoatm Incref = 0.0 EndGroup EndObject -------------------------------- Example 4 (Used to process Clementine UVVIS filter "a" data): Object = PhotometricModel Group = Algorithm PhtName = LunarLambertMcEwen EndGroup EndObject Object = NormalizationModel Group = Algorithm NormName = MoonAlbedo D = 0.0 E = -0.222 F = 0.5 G2 = 0.39 H = 0.062 Bsh1 = 2.31 Wl = 1.0 Xb1 = 1.0 Xb2 = 1.0 EndGroup EndObject -------------------------------- Example 5 (Used to process Clementine UVVIS filter "b" data): Object = PhotometricModel Group = Algorithm PhtName = LunarLambertMcEwen EndGroup EndObject Object = NormalizationModel Group = Algorithm NormName = MoonAlbedo D = 0.0 E = -0.218 F = 0.5 G2 = 0.4 H = 0.054 Bsh1 = 1.6 Wl = 1.0 Xb1 = 1.0 Xb2 = 1.0 EndGroup EndObject -------------------------------- Example 6 (Used to process Clementine UVVIS filter "cde" data): Object = PhotometricModel Group = Algorithm PhtName = LunarLambertMcEwen EndGroup EndObject Object = NormalizationModel Group = Algorithm NormName = MoonAlbedo D = 0.0 E = -0.226 F = 0.5 G2 = 0.36 H = 0.052 Bsh1 = 1.35 Wl = 1.0 Xb1 = 1.0 Xb2 = 1.0 EndGroup EndObject -------------------------------- Example 7 (Used for Mars red filter data to apply empirical photometric models): Object = PhotometricModel # For Mars red filter images # The phase angles at which the coefficient values for the Lunar Lambert # Empirical (LunarLambertEmpirical) L and the Minnaert Empirical K approximation are # calculated, along with the brightness (phase curve) values at those # points (ALL ON ONE LINE!) Group = Algorithm PhtName = LunarLambertEmpirical PhaseList = "0.,10.,20.,30.,40.,50.,60.,70.,80.,90.,100.,110.,120.,130.,140.,150.,160.,170.,180." LList = "0.946,0.748,0.616,0.522,0.435,0.350,0.266,0.187,0.118,0.062,0.018,-0.012,-0.027, -0.035,-0.036,-0.037,-0.031,-0.012,-0.010" PhaseCurveList = "0.1578,0.1593,0.1558,0.1484,0.1391,0.1292,0.1194,0.1099,0.1008,0.09176, 0.08242,0.07234,0.06165,0.05106,0.04091,0.03137,0.02171,0.01038,0." EndGroup Group = Algorithm PhtName = MinnaertEmpirical PhaseList = "0.,10.,20.,30.,40.,50.,60.,70.,80.,90.,100.,110.,120.,130.,140.,150.,160.,170.,180." KList = "0.518,0.595,0.660,0.709,0.753,0.796,0.837,0.875,0.904,0.922,0.926,0.935,0.954,0.986, 1.019,1.063,1.099,1.095,1.090" PhaseCurveList = "0.1574,0.1582,0.1546,0.1470,0.1375,0.1273,0.1174,0.1077,0.09797,0.08750, 0.07594,0.06466,0.05471,0.04665,0.03935,0.03339,0.02642,0.01482,0." EndGroup EndObject References: Chandrasekhar, S., 1960. Radiative Transfer. Dover, 393 pp. Hapke, B. W., 1981. Bidirectional reflectance spectroscopy 1: Theory. J. Geophys. Res., pp. 86,3039-3054. Hapke, B., 1984. Bidirectional reflectance spectroscopy3: Corrections for macroscopic roughness. Icarus, 59, pp. 41-59. Hapke, B., 1986. Bidirectional reflectance spectroscopy 4: The extinction coefficient and the opposition effect. Icarus, 67, pp. 264-280. Johnson, J. R., et al., 1999, Preliminary Results on Photometric Properties of Materials at the Sagan Memorial Station, Mars, J. Geophys. Res., 104, 8809. Kirk, R. L., Thompson, K. T., Becker, T. L., and Lee, E. M., 2000. Photometric modelling for planetary cartography. Lunar Planet. Sci., XXXI, Abstract #2025, Lunar and Planetary Institute, Houston (CD-ROM). Kirk, R. L., Thompson, K. T., and Lee, E. M., 2001. Photometry of the martian atmosphere: An improved practical model for cartography and photoclinometry. Lunar Planet. Sci., XXXII, Abstract #1874, Lunar and Planetary Institute, Houston (CD-ROM). McEwen, A. S., 1991. Photometric functions for photoclinometry and other applications. Icarus, 92, pp. 298-311. Thorpe, T. E., 1973, Mariner 9 Photometric Observations of Mars from November 1971 through March 1972, Icarus, 20, 482. Tomasko, M. G., et al., 1999, Properties of Dust in the Martian Atmosphere from the Imager on Mars Pathfinder, J. Geophys. Res., 104, 8987.
Name | Description |
---|---|
FROM | Input cube file |
TO | Output cube file |
FROMPVL | Input PVL file |
Name | Description |
---|---|
CHNGPAR | Change parameter string |
Name | Description |
---|---|
MAXEMISSION | Maximum emisson angle to trim image |
MAXINCIDENCE | Maximum incidence angle to trim image |
USEDEM | Specify if DEM photometric angels will be used to trim image |
Name | Description |
---|---|
ANGLESOURCE | Source of photometric angles: ELLIPSOID, DEM, CENTER, or FILE |
PHASE_ANGLE_FILE | Phase angle cube file |
INCIDENCE_ANGLE_FILE | Incidence angle cube file |
EMISSION_ANGLE_FILE | Emission angle cube file |
PHASE_ANGLE | Center phase angle |
INCIDENCE_ANGLE | Center incidence angle |
EMISSION_ANGLE | Center emission angle |
Name | Description |
---|---|
PHTNAME | Photometric model to be used |
THETA | Macroscopic roughness angle |
WH | Single scattering albedo |
HG1 | Hapke Henyey Greenstein coefficient |
HG2 | Hapke Henyey Greenstein Coefficient |
BH | Hapke Legendre coefficient |
CH | Hapke Legendre coefficient |
HH | Hapke opposition surge |
B0 | Hapke opposition surge |
ZEROB0STANDARD | Specifies if opposition surge is set to zero under standard conditions |
L | Lunar-Lambert function weight |
K | Minnaert function exponent |
PHASELIST | Empirical functions phase angle list |
KLIST | Minnaert Empirical function limb darkening parameter list |
LLIST | Lunar Lambert Empirical function limb darkening parameter list |
PHASECURVELIST | Empirical functions phase curve (brightness) value list |
Name | Description |
---|---|
ATMNAME | Atmospheric model to be used |
NULNEG | Specifies if negative values will be set to NULL |
TAU | Optical depth of atmosphere |
TAUREF | Reference value of tau |
HGA | Henyey Greenstein coefficient |
WHA | Single scattering albedo |
BHA | Legendre coefficient |
HNORM | Atmospheric shell thickness |
Name | Description |
---|---|
NORMNAME | Normalization model to be used |
INCREF | Reference incidence angle |
INCMAT | Photometric transition incidence angle |
THRESH | Amplification threshold |
ALBEDO | Albedo |
D | Albedo normalization parameter |
E | Albedo normalization parameter |
F | Albedo normalization parameter |
G2 | Albedo Normalization Parameter |
H | Albedo normalization parameter |
XMUL | Radiance to reflectance or calibration factor |
WL | Wavelength |
BSH1 | Albedo normalization parameter |
XB1 | Albedo normalization parameter |
XB2 | Albedo normalization parameter |
This is the input filename that will be photometrically corrected.
Type | cube |
---|---|
File Mode | input |
Filter | *.cub |
This output file will contain the results of the photometric correction.
Type | cube |
---|---|
File Mode | output |
Pixel Type | real |
This text file contains the parameter names and values to be used to perform the photometric correction.
Type | filename |
---|---|
File Mode | input |
Default Path | $ISISROOT/appdata/templates/photometry |
Internal Default | None Specified |
Filter | *.pvl |
Chngpar is used to enter a string of parameter names and values enclosed in quotes that will be added to or replaces the pre-defined parameter values. PLEASE NOTE: Any parameter names used in the CHNGPAR string input MUST be spelled out completely and without any errors. Otherwise, they will be ignored by the program.
Example:
photomet from=f1.cub to=pho.cub frompvl=my.pvl chngpar="tau=0.5 tauref=30"
Type | string |
---|---|
Default | None |
Internal Default | None |
The maximum number of degrees allowed for the emission angle in order to retain the data. This number must be between 0.0 and 90.0.
Type | double |
---|---|
Default | 90.0 |
Minimum | 0.0 (inclusive) |
Maximum | 90.0 (inclusive) |
The maximum number of degrees allowed for the incidence angle in order to retain the data. This number must be between 0.0 and 90.0.
Type | double |
---|---|
Default | 90.0 |
Minimum | 0.0 (inclusive) |
Maximum | 90.0 (inclusive) |
This specifies if the image will be trimmed based on the photometric angles obtained from the ellipsoid (default) or the DEM surface.
The ellipsoid is retrieved from the IAU/NAIF target body file, which is defined within the cube's kernel group as the TargetAttitudeShape. If this parameter is set to false, then the photometric angles will be obtained from the ellipsoidal surface.
The photometric angles obtained from the DEM surface (shape model) for each pixel are obtained using an ellipsoid defined by the radius obtained from the DEM shape model. Note that photomet does not trim using local slopes.
Type | boolean |
---|---|
Default | FALSE |
The incidence, emission, and phase angles are determined based on
the source defined by the user. The available options are listed
below:
Type | combo | |||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Default | ELLIPSOID | |||||||||||||||||||||
Internal Default | ELLIPSOID | |||||||||||||||||||||
Option List: |
|
This file must contain the phase angle information for the input cube.
Type | cube |
---|---|
File Mode | input |
Pixel Type | real |
Internal Default | No file |
This file must contain the incidence angle information for the input cube.
Type | cube |
---|---|
File Mode | input |
Pixel Type | real |
Internal Default | No file |
This file must contain the emission angle information for the input cube.
Type | cube |
---|---|
File Mode | input |
Pixel Type | real |
Internal Default | No file |
The center phase angle to use if the CENTER_FROM_USER option is chosen.
Type | double |
---|---|
Default | 0.0 |
Minimum | 0.0 (inclusive) |
Maximum | 180.0 (inclusive) |
The center incidence angle to use if the CENTER_FROM_USER option is chosen.
Type | double |
---|---|
Default | 0.0 |
Minimum | 0.0 (inclusive) |
Maximum | 90.0 (inclusive) |
The center emission angle to use if the CENTER_FROM_USER option is chosen.
Type | double |
---|---|
Default | 0.0 |
Minimum | 0.0 (inclusive) |
Maximum | 90.0 (inclusive) |
Specify the name of the surface photometric function model to apply
to the input image. The available options are the following:
Band | Wh | B0 | Hh | Hg1 | Hg2 |
---|---|---|---|---|---|
Red | 0.52 | 0.025 | 0.17 | 0.213 | 1.0 |
Green | 0.29 | 0.29 | 0.17 | 0.19 | 1.0 |
Blue | 0.16 | 0.995 | 0.17 | 0.145 | 1.0 |
Type | combo | |||||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Default | FROMPVL | |||||||||||||||||||||||||||||||||
Internal Default | FROMPVL | |||||||||||||||||||||||||||||||||
Option List: |
|
The "macroscopic roughness" of the surface as it affects the photometric behavior, used for Hapkehen or Hapkeleg. This is the RMS slope at scales larger than the distance photons penetrate the surface but smaller than a pixel. See Hapke (1986). The roughness correction, which is evaluated if theta is given any value other than 0.0, but is extremely slow. See Hapke (1986).
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | 0.0 (inclusive) |
Maximum | 90.0 (inclusive) |
The Hapke single scattering albedo of surface particles, see Hapke (1981).
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | 0.0 (exclusive) |
Maximum | 1.0 (inclusive) |
Asymmetry parameter used in Hapke Henyey Greenstein model for the scattering phase function of single particles in the surface. See Hapke (1981). The two parameter Henyey Greenstein function is:
P(phase)=(1-hg2) * (1-hg1**2)/(1+hg1**2+2*hg1*cos(phase))**1.5 + hg2 * (1-hg1**2)/(1+hg1**2-2*hg1*cos(phase))**1.5
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | -1.0 (exclusive) |
Maximum | 1.0 (exclusive) |
The Hapke Henyey Greenstein coefficient for single particle phase function. The second parameter of the two-parameter Henyey-Greenstein model for the scattering phase function of single particles in the surface. This parameter controls the proportions in a linear mixture of ordinary Heneyey Greenstein phase functions with asymmetry parameters equal to +hg1 and -hg1. See HG1 for the full formula.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | 0.0 (inclusive) |
Maximum | 1.0 (inclusive) |
The Hapke Legendre coefficient for single particle phase function. A two-term Legendre polynomial is used for the scattering phase function of single particles in the surface:
P(phase) = 1 + bh * p1(cos(phase)) + ch * p2(cos(phase))Bh is not to be confused with the Legendre coefficient bha of the phase function for atmospheric particles, used when atmname=anisotropic1 or anisotropic2.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | -1.0 (exclusive) |
Maximum | 1.0 (exclusive) |
The Hapke Legendre coefficient for single particle phase
function. A two-term Legendre polynomial is used for the scattering
phase function of single particles in the surface:
P(phase) = 1 + bh * p1(cos(phase)) + ch * p2(cos(phase))
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | -1.0 (exclusive) |
Maximum | 1.0 (exclusive) |
The Hapke opposition surge component. The width parameter for the opposition effect for the surface if Hapkehen or Hapkeleg is used. See Hapke (1984).
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | 0.0 (inclusive) |
The Hapke opposition surge component. The magnitude of the opposition effect for the surface if Hapkehen or Hapkeleg is used. See Hapke (1984).
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | 0.0 (inclusive) |
This specifies if the opposition surge component B0 is set to zero during the standard conditions phase. The program will automatically default to "true" if "ZEROB0STANDARD" is not defined in the PVL FILE when the "READFROMPVL" option is selected, and the user did not choose either "FALSE" or "TRUE" option.
Type | string | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Default | READFROMPVL | ||||||||||||
Option List: |
|
The Lunar Lambert function weight that governs limb-darkening in the lunar lambert photometric function:
Func=(1-L)*u0 + 2*L*u0/(u0+u)The values generally fall in the range from 0 (Lambert function) to 1 (Lommel-Seeliger or "lunar" function).
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
The Minnaert function exponent that governs limb-darkening in the Minnaert photometric function:
Func=u0**K * u**(K-1)The values generally fall in the range from 0.5 ("lunar-like", almost no limb darkening) to 1.0 (Lambert function).
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | 0.0 (inclusive) |
The Minnaert Empirical and Lunar Lambert Empirical function phase angle list entered as a comma delimited string describing how the parameters of the empirical function vary with phase angle. See "$ISISROOT/appdata/templates/photometry/marsred.pvl" for an example.
Type | string |
---|---|
Default | No List |
Internal Default | No List |
The Minnaert Empirical function exponent list of limb darkening values entered as a comma delimited string that describes how the parameters of the empirical function vary with phase angle. See "$ISISROOT/appdata/templates/photometry/marsred.pvl" for an example.
Type | string |
---|---|
Default | No List |
Internal Default | No List |
The Lunar Lambert Empirical function parameter list of limb darkening values entered as a comma delimited string that describes how the parameters of the empirical function vary with phase angle. See "$ISISROOT/appdata/templates/photometry/marsred.pvl" for an example.
Type | string |
---|---|
Default | No List |
Internal Default | No List |
The Minnaert Empirical or Lunar Lambert Empirical function phase curve list of brightness values corresponding to a set of phase angles defined in the PHASELIST parameter. See "$ISISROOT/appdata/templates/photometry/marsred.pvl" for an example.
Type | string |
---|---|
Default | No List |
Internal Default | No List |
This is the name of the atmospheric photometric function model to be
applied. The models ending with "1" use a first order scattering
approximation. Those ending with "2" use a second order scattering
approximation, and are slower but more accurate than the first order
scattering approximation. The atmospheric correction can be used with
only three atmospheric normalization models: albedoatm, shadeatm, and topoatm. See
Kirk et al. (2001).
The table below are photometric parameter values for Mars,
adopted from Tomasko et al. (1999):
Band | Wha | Hga |
---|---|---|
Red | 0.95 | 0.68 |
Blue | 0.76 | 0.78 |
Type | combo | ||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Default | NONE | ||||||||||||||||||||||||
Internal Default | NONE | ||||||||||||||||||||||||
Option List: |
|
This specifies if negative values after removal of atmospheric effects will be set to NULL. Negative values are only generated in modes that include atmospheric correction and occur when the optical depth "tau" is overestimated, so that the atmospheric radiance subtracted from the image is brighter than the darkest observed pixels. In this case "tau" should be decreased until no negative values are present in the output file.
Type | string | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Default | READFROMPVL | ||||||||||||
Option List: |
|
The normal optical depth of the atmosphere.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | 0.0 (inclusive) |
The reference value of tau to which the image will be normalized. This would normally be 0.0 unless one is interested in simulating a hazy atmosphere scene.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | 0.0 (inclusive) |
The coefficient of single particle Henyey Greenstein phase function. Henyey-Greenestein asymmetry parameter for atmospheric particle phase function, used in hapkeatm1 and hapkeatm2 atmospheric models. Not to be confused with corresponding parameter hg1 for the surface particles.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | -1.0 (exclusive) |
Maximum | 1.0 (exclusive) |
The single scattering albedo of atmospheric particles.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | 0.0 (exclusive) |
Maximum | 1.0 (inclusive) |
The coefficient of the single particle Legendre phase function. Coefficient of p1 (cosine) term of atmospheric particle phase function, used in anisotropic1 and anisotropic2 atmospheric models. Not to be confused with corresponding coefficient bh for the surface particles.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | -1.0 (inclusive) |
Maximum | 1.0 (inclusive) |
The atmospheric shell thickness normalized to the planet radius, used to modify angles to get more accurate path lengths near the terminator (Ratio of scale height to the planetary radius). For Mars MDIM2.1 mosaic "0.003" was defined, which is the only planet for which the atmospheric modes are currently used.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | 0.0 (inclusive) |
This is the name of the normalization model to be performed
Type | combo | ||||||||||||||||||||||||||||||
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Default | FROMPVL | ||||||||||||||||||||||||||||||
Internal Default | FROMPVL | ||||||||||||||||||||||||||||||
Option List: |
|
This is the reference incidence angle to which the image will be normalized. Most normalization modes attempt to normalize the appearance of the surface to a set of standard conditions, in particular, a fixed incidence angle given by the incref parameter. In most cases, a value of 0 degrees is used for albedo and albedoatm normalization modes, though 30 degrees is sometimes used. Incref of 0 degrees is also the usual choice for specifying the albedo of shaded relief images calculated with shade and shadeatm normalization modes. Incref of 30 degrees is the standard value for topographic normalization modes topo and topoatm because topographic shading disappears at 0 degree incidence angle and cannot be normalized to this value.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | 0.0 (inclusive) |
Maximum | 90.0 (exclusive) |
This specifies the incidence angle where albedo normalization transitions to topographic normalization. When mixed normalization mode is selected, the image will be normalized so that albedo variation is constant for small incidence angles and topographic shading is constant for large incidence angles. This parameter must be set by trial and error to achieve the best appearance, because it depends on the relative amount of albedo variations and shading for any given planet or satellite. The value of the albedo parameter must also be adjusted for this mode to match the mean brightness of the high incidence angle region to that of the data at lower incidence angles.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Minimum | 0.0 (inclusive) |
Maximum | 90.0 (exclusive) |
This sets upper limit on the amount of amplification in regions of small incidence angle. Operating modes that involve topographic normalization topo, topoatm, and mixed options will amplify variations in the input image in regions of small incidence angle where the shading in the input image is weak. Thresh is an upper limit on the amount of amplification that will be attempted. If it is set too low, low-incidence areas of the image may appear bland, but if thresh is set too high these regions may contain amplified noise rather than useful shading information.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
The albedo to which the image will be normalized. The value of the desired model albedo, used with shade, topo, mixed, shadeatm, and topoatm. This is the albedo (I/F value at incidence angle defined for incref and zero phase) used to simulate a shaded relief image when shade or shadeatm normalization models are used. For the other modes, it is the albedo that the image will be normalized to have. The program stats can be run to get the average albedo of an input image, but for constructing mosaics the same value of albedo should be used for all images in order to achieve a uniform result.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
This is the empirically derived coefficient for the albedo dependent phase function normalization parameter.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
This is the empirically derived coefficient for the albedo dependent phase function normalization parameter.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
This is the empirically derived coefficient for the albedo dependent phase function normalization parameter.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
This is the empirically derived coefficient for the albedo dependent phase function normalization parameter.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
This is the empirically derived coefficient for the albedo dependent phase function normalization parameter.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
This is used to convert radiance to reflectance, or apply a calibration fudge factor.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
The wavelength in micrometers of the image being normalized.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
This is the empirically derived coefficient for the albedo dependent phase function normalization parameter.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
This is the empirically derived coefficient for the albedo dependent phase function normalization parameter.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
This is the empirically derived coefficient for the albedo dependent phase function normalization parameter.
Type | string |
---|---|
Default | None Specified |
Internal Default | None Specified |
Photometric correction with any valid photometric angles
Example GUI Screenshot of GUI version of the application. The default value for the MAXEMISSION and MAXINCIDENCE parameters is 90.0. The parameter values were loaded into the appropriate parameter names using the drop-down menu for the "FROMPVL" parameter name. |
Input file
Parameter Name:
FROM
Screenshot of the input image before the photometric correction has been performed. |
Example of a PVL file | The PVL file contains the photometric parameters to be applied to the input cube file. Load the PVL file parameters using the photomet GUI drop-down menu and add the additional required parameter value for "ALBEDO." |
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Output file
Parameter Name:
TO
Screenshot of the output image after the photometric correction. Notice the features have consistent tones except near the limb where the pixels are brighter because it is over-corrected. A histogram stretch is applied automatically when the image is displayed, so the image appears darker due to the higher DN values at the terminator. |
Photometric correction with mixed normalization option
Example GUI Screenshot of GUI version of the application. The default value for MAXEMISSION and MAXINCIDENCE parameters is 90.0, but the INCMAT parameter is set to 75 degrees. |
Input file
Parameter Name:
FROM
Screenshot of the input image before the photometric correction has been performed. |
Example of the PVL file | The PVL file containing the photometric parameters to be applied to the input cube. Load the PVL file parameters using the photomet GUI and add additional required parameter values for "INCMAT" and "ALBEDO." |
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Output file
Parameter Name:
TO
Screenshot of the output image after the photometric correction. Notice the limb area was over-corrected in the previous example, but now shows more consistent tones in the output image. |
Photometric correction with mixed normalization and trim options
Example GUI Screenshot of GUI version of the application. The MAXEMISSION is set to 90.0; the MAXINCIDENCE and INCMAT parameters are set to 75.0 degrees. |
Input file
Parameter Name:
FROM
Screenshot of the input image before the photometric correction has been performed. |
Example of the PVL file | The PVL file containing the photometric parameters to be applied to the input cube file. Load the PVL file parameters using the photomet GUI and add additional required parameter values for "INCMAT" and "ALBEDO." |
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Output file
Parameter Name:
TO
Screenshot of the output image after the photometric correction. Notice the limb area, where it was over-corrected in the first example, has been trimmed. |
Photometric correction using maximum emission and incidence angle parameters
Example GUI Screenshot of GUI version of the application. Notice the MAXEMISSION and MAXINCIDENCE parameters are changed from the default value of 90.0. |
Input file
Parameter Name:
FROM
Screenshot of the input image before the photometric correction has been performed. |
Input PVL file | The PVL file contains the input photometric parameters for the input file. |
---|
Output file
Parameter Name:
TO
Screenshot of the output image after the photometric correction. Notice the output image has been trimmed based on the photometric angles defined by the user. |
Photometric correction using maximum emission and incidence angle parameters as well as anglesource and usedem parameters.
This example shows the photometric correction of a cube file by setting the maximum emission angle to 75.0 degrees and the maximum incidence angle to 85.0 degrees. The photometric model being used is MINNAERT and the normilization model is ALBEDO. The usedem parameter is describing how to trim the image. In this case the trimming is being done using the radius obtained from the DEM. The anglesource parameter describes how to calculate the photometric angles. In this example the calculation is also being done using the DEM.
Example GUI Screenshot of GUI version of the application. Notice the MAXEMISSION has changed from the default value of 90.0, usedem is set to it's default, and anglesource is set to DEM. |
Input file
Parameter Name:
FROM
Screenshot of the input image before the photometric correction has been performed. |
Output file
Parameter Name:
TO
Screenshot of the output image after the photometric correction. Notice the output image has been trimmed based on the photometric angles defined by the user. |
Photometric corrections using a three-step approach for MDIM2.1 of Mars
Sample script | This script contains the three-step processing sequence of programs that need to be executed for the three test images. |
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Collage of images
The images shown are subareas at 1:1 scale to emphasize the result of the
photometric correction at each stage. There are four rows in the image
collage containing the following:
|
Tammy Becker | 1989-02-15 | Original version - based on Tammy Becker's photom/photompr programs which were later converted to Randy Kirk's photomet |
Janet Barrett | 2008-03-07 | Added code to acquire the BandBin Center keyword from the input image. This value is needed in case the user chooses the MoonAlbedo normalization method. |
Steven Lambright | 2008-05-13 | Removed references to CubeInfo |
Jeannie Walldren | 2009-01-08 | Added MAXEMISSION and MAXINCIDENCE parameters. Modified code to set off-target pixels to NULL. Added appTests for new parameters. Added user documentation examples. |
Eric Hyer | 2010-11-10 | Added USEDEM parameter. |
Janet Barrett | 2010-11-22 | Added error check for situations where there is not an intersection with the DEM and the local photometric angles are requested. |
Janet Barrett | 2010-11-23 | Added capability to use both ellipsoid and DEM photometric angles in atmospheric corrections. This provides the ability to do shading using a DEM surface. |
Janet Barrett | 2011-02-22 | The USEDEM parameter has been removed and the ANGLESOURCE parameter has been added. The ANGLESOURCE parameter lets you specify the source where the photometric angles will come from: ellipsoid, DEM, or center of image. |
Janet Barrett | 2011-03-29 | The CENTER option of the ANGLESOURCE parameter has been removed and the CENTER_FROM_IMAGE, CENTER_FROM_LABEL and CENTER_FROM_USER options have been added. This allows the user to determine where the center photometric angles will come from. |
Janet Barrett | 2011-09-23 | The following changes were made to the program for the ISIS3.3.0 release: 1) The PHOPAR parameter name was changed to FROMPVL - this was done to have consistent parameter names throughout the photometry software. 2) All radio button options are now accessed through drop down menus. The only radio button options that existed prior to this release were those for choosing the ANGLESOURCE. In order to use any of the drop down menus, click on the drop down menu and hold the mouse button down while navigating to the choice that you want. 3) Added a USEDEM option which will let you determine how the trim is performed. If you don't check the USEDEM box, then trimming is performed based on the photometric angles of the ellipsoid. If you check the USEDEM box, then the trimming is performed based on the photometric angles of the DEM (if one is specified in the image labels). If there is no DEM associated with your FROM file, then the default is to use the ellipsoid. 4) The program now lets you specify the photometric model, atmospheric model, and normalization model through the PHTNAME, ATMNAME, and NORMNAME drop down menus. Prior to this release, you were forced to provide an input PVL file with all of the model information in it. You can now provide the model information through the PVL, the GUI, or a combination of both. If you provide a FROMPVL file, then you need to use the GUI to specify which model(s) to use from that file. If you change any of the model-specific parameters in the GUI, then they will override the values in the FROMPVL file. 5) The BHAREF, HGAREF, and WHAREF parameters have been removed because they were obsolete. 6) The NONORMALIZATION model was removed because it duplicated the functionality of the SHADE model. 7) More photometric models have been added. The Hapke Legendre, Minnaert Empirical, and Lunar Lambert Empirical models have been added. The Minnaert Empirical model has parameters PHASELIST, PHASECURVELIST, and KLIST associated with it. The information for the new parameters is a list of comma delimited values (phase angle goes in PHASELIST, brightness values go in PHASECURVELIST, and limb darkening values go in KLIST). The Lunar Lambert Empirical model has parameters PHASELIST, PHASECURVELIST, and LLIST where LLIST is similar to the KLIST parameter for Minnaert Empirical. 8) A USEDEM parameter has been added which allows the user to determine which photometric angles to use for trimming. If the USEDEM parameter is set to false, then the photometric angles of the ellipsoid are used. If USEDEM is set to true, then the photometric angles of the DEM shape model are used for trimming. 9) Helper buttons were added to the FROMPVL to allow you to View a PVL or to Load a PVL. PLEASE NOTE: When loading a Minnaert Empirical or Lunar Lambert Empirical model from a PVL, only the first value will be loaded into the GUI. This is a known problem and will be fixed in the next patch or release to ISIS. 10) ***NOTE*** The Minnaert Empirical and Lunar Lambert Empirical models do not load properly from a PVL file when using the Load PVL helper button. This is a known problem and will be fixed in the next patch or release of ISIS. |
Janet Barrett | 2011-11-04 | The ZEROB0STANDARD parameter for the Hapke models was not added to the new update of photomet during the last release. This parameter is responsible for determining if the Hapke opposition surge component B0 is set to zero when calculations are based on standard conditions. This parameter has been added to the new interface to photomet. |
Janet Barrett | 2012-01-10 | The program was fixed to make it backwards compatible with older PVL files. If you tried running this program with an older PVL, then you most likely got the following error message "A Normalization model must be specified before running this program." This message would have occurred even if you had a Normalization model specified in your FROMPVL file. This problem has been fixed. If your FROMPVL file specifies a Normalization model, then you aren't required to specify one through the program interface as well. |
Janet Barrett | 2012-05-04 | A new BACKPLANE option was added to ANGLESOURCE. This BACKPLANE option allows you to input photometric angle information using separate ISIS cube files. Files containing geometric, photometric, etc. information pixel by pixel for the input image file are normally referred to as backplanes. This option was added to support image data that does not have a camera model associated with it. If you have a way to generate the photometric angles for such data, then you will be able to do photometric correction on it. This option is also very useful for speeding up the processing done by photomet. If you have all the photometric information pre-computed, then this information no longer needs to be generated every time the program is run. You can input photometric information using a combination of files and photometric angle constants. For example, if you have a file containing the phase angle for every pixel, a file containing the incidence angle for every pixel, and you know that the emission angle is 0.0 for every pixel, then you can use the PHASE_ANGLE_FILE, INCIDENCE_ANGLE_FILE, and EMISSION_ANGLE fields to input the 2 file names and the emission angle constant. |
Ella Mae Lee | 2012-10-05 | Improved the documentation, reference Mantis issue #453, #843 |
Janet Barrett | 2012-10-24 | The following changes were made to the program: 1) Added a new parameter, CHNGPAR, which allows the user to change any of the model- related parameter settings without having to specify the model name on the command line or in the GUI. Before the CHNGPAR parameter was added, you could only change a model-related parameter on the command line or in the GUI if you also specified the model name using the PHTNAME, ATMNAME, or NORMNAME parameter. Any value you set using the CHNGPAR parameter will override changes that are specified in the GUI. Any value that is changed through the GUI will override values specified in the FROMPVL file. **PLEASE NOTE**: Any parameter that you type into the CHNGPAR string MUST be spelled correctly and using the full name (no partial parameter names). Otherwise, the program will not recognize the parameter and it won't get used. 2) Added new output groups to the print.prt log file so that the user can see exactly which values were used to run photomet. The new groups that get written to the print.prt file include NormalizationModelParametersUsed, AtmosphericModelParametersUsed, and PhotometricModelParametersUsed. 3) Fixed photomet so that the INCMAT parameter is no longer required for the ALBEDO normalization model. The INCMAT parameter is not used by the ALBEDO normalization model, so the user is no longer required to input an INCMAT value for that model. 4) Fixed a problem which was causing the NULNEG and ZEROB0STANDARD parameters to be loaded incorrectly if specified in the FROMPVL file. 5) Added a more meaningful error message when a normalization model is not specified by the user either through the GUI, command line, or FROMPVL file. 6) Changed the ZEROB0STANDARD parameter name to ZEROB0ST. This was to help prevent the user from needing to resize the GUI each time they opened it because the parameter name was too long. We are maintaining backwards compatibility by supporting both ZEROB0STANDARD and ZEROB0ST in the photomet code. This will allow you to run a script with the old parameter name without any problems. |
Janet Barrett | 2012-12-07 | PLEASE NOTE (in reference to change made on 2012-10-24): The backwards compatibility for the shorter ZEROB0ST parameter name has not been fully implemented in ISIS. As a result, this change has been removed and the full ZEROB0STANDARD parameter name must be used. Support for aliases (deprecated values) must be fully implemented in ISIS before the shorter parameter name (ZEROB0ST) will be available. Fixes #1288. |
Lynn Weller | 2013-02-25 | Removed links to applications imbedded in text and replaced with italicized application name. Added application links to the "Related Objects and Documents" section of the documentation. Fixes mantis ticket #1525. |
Kelvin Rodriguez | 2016-08-24 | Added cast to void on 'changePar.simplified()' function call to silience unused return value warnings on OS X |
Curtis Rose | 2016-11-16 | Decoupled ANGLESOURCE and USEDEM parameters. They were working incorrectly before and were tangled together a bit. They are separated now and working as expected. Anglesource DEM makes the photometric calculations based on the DEM of the image if it exists. Anglesource ELLIPSOID makes the photometric calculations based on the radius obtained from the DEM shape model. Usedem true trims the image using the photometric calculations on the radius obtained from the DEM shape model. Usedem false trims the image using the from the IAU/NAIF target body file, which is defined within the cube's kernel group as the TargetAttitudeShape. Fixes #4180. |
Lauren Adoram-Kershner | 2019-11-07 | Added a warning when the 'DEM' angle source option is used with 'mixed' or 'topo' normalization method. Fixes #3451 and #3452. |