ISIS Photometry and Photoclinometry Software

We are currently working under the NASA Planetary Geology and Geophysics program of planetary cartography to extend the ISIS capabilities having to do with planetary photometry. The cornerstone of this effort is the release of programs for doing two-dimensional photoclinometry (shape-from-shading) to produce digital elevation models from single images. In addition, the photometric normalization program photomet, used for making image mosaics, now has improved documentation and a user interface that is consistent with the photoclinometry programs (photomet was released in 2000 and is substantially more flexible than the previous generation of normalization programs.) Several programs for estimating the photometric parameters needed for photoclinometry and photometric processing have been implemented, and others are currently being developed.

This page provides information about the ISIS photoclinometry and photometry programs, how to get them, how to use them, and how to get help. It will be updated periodically as new programs are released.

Photoclinometry Software

Program	Updated	Description
pc2d	7/23/03	Perform two-dimensional photoclinometry in general case, with graphical user interface for control of the iterative calculation. (multiple bugs fixed 7/23/03)
pcsi	7/23/03	Perform photoclinometry non-interactively (fixed number of iterations) for "smart interpolation" of a low-resolution topo model (multiple bugs fixed 7/23/03)
pcinfo	4/4/03	Calculate memory requirements for pc2d/pcsi

Photometric Normalization Software

Program	Updated	Description
photomet	7/23/03	Use surface (and atmosphere) model to normalize an image so albedo variations or topographic shading are independent of illumination. Improved documentation. Now includes modes for output of simulated (shaded relief) image with or without atmosphere and can use a DEM (Digital Elevation Model) rather than ellipsoid to calculate photometric angles if desired.

Photometric Fitting Software

Program	Updated	Description
pho_emp_global	3/14/03	Find empirical photometric function (Minnaert or Lunar-Lambert) parameters that best fit a given Hapke model over the whole disk, as a function of phase angle
pho_emp_local	3/14/03	Find empirical photometric parameters to fit a Hapke model at the incidence, emission, and phase of a single image
shadow_tau	3/14/03	Calculate atmospheric optical depth for photometric processing from tabulated shadow brightness
shade_tau	7/23/03	Calculate optical depth by minimizing residual shading across an image upon normalization. (algorithm improved 7/23/03)
pc_fit_inverse.pl	7/23/03	Calculate atmospheric haze for photoclinometry by doing trial clinometry and matching to a priori topography. PERL script
pc_fit_forward.pl	7/23/03	Calculate atmospheric haze for photoclinometry by comparing real image to simulated image calculated from DEM. PERL script

Related Software

Program	Updated	Description
lev1prop	7/23/03	Propagate illumination and viewing geometry info from a representative image to a mosaic so it can be used for photoclinometry. (bug fixed 7/23/03)
cube2ascii	7/23/03	Output pixel values from an ISIS cube as an ascii (text) table. Useful for fitting atmospheric haze by spreadsheet modeling.
levgetlab	7/23/03	Used to set keyword PHOTO_DEM to the name of a DEM file that will be used to calculate photometric angles.
lev1geoplane levgeoplane	7/23/03	Can now create backplanes with incidence, emission angles calculated from a DEM if desired.
linfit	7/23/03	Perform linear regression fit of one image on one or two others. Used in photometric fitting. (additional outputs added 7/23/03)
cherdpi	7/23/03	Creates a file with topography that would be 1% brighter than a level surface in a given image. Used by pcfit_inverse.pl for fitting atmospheric haze.

Obtaining and Setting Up the Software

The Integrated Software for Imagers and Spectrometers (ISIS) home page provides information about the software, how to register as a user, how to acquire the software, and how to obtain help with the software. The web site is being updated, so it would be best to start from the ISIS home page.

If you are not already a registered ISIS user, start by registering as an ISIS user, then acquire the software and install ISIS.

Update your ISIS installation by using RSYNC to be sure you have the latest photoclinometry/photometry software . Repeat as needed to obtain new or updated programs.

The graphical user interface for pc2d requires that several environment variables not used by other ISIS programs be set. An update to the ISIS software will now automatically set these environment variables.

Help!

As with all ISIS software, brief descriptions of the overall function of each program and its input parameters are available in the TAE environment. The photometric normalization and fitting programs are simple enough that the TAE documentation should suffice to use the software. Hapke photometric parameters for Mars are included in the documentation, and empirical parameters can be determined from these with pho_emp_global or pho_emp_local. A useful compilation of Hapke parameters from the literature for other solar-system bodies is given by McEwen (1991) Photometric Functions for Photoclinometry and Other Applications, Icarus, 92, pp. 298–311.

The photoclinometry software, particularly the interactive program pc2d, is sufficiently complicated that additional documentation is needed. A preliminary draft of the user manual PC User Guide (PDF format) provides a summary of information needed to use the program, including pre-and post-processing, setting input parameters, using the graphical user interface to control the program, and troubleshooting. We plan to update and improve this document in response to user feedback.

A recent conference paper Photoclinometry Made Simple ...? provides additional information about the requirements, programs, and workflow for photoclinometry. Simulations to assess the accuracy of elevation models from photoclinometry are described in the abstract High-Resolution Topomapping of Candidate MER Landing Sites with MOC: New Results and Error Analyses. , which also illustrates the use of the method to assess small-scale martian topography. A more detailed paper, High-Resolution Topomapping Of Candidate Mer Landing Sites With Mars Orbiter Camera Narrow-Angle Images , describing the photoclinometry algorithms and accuracy assessments is now available.

It is important to recognize that photoclinometry is a modeling process employing complex software. Practice will be required to run the software, and judgement is needed to achieve reliable results. We have made every effort to eliminate bugs from the software and make the user interface as clear as possible, but users should understand that they are participating in beta testing of an evolving software product. We welcome user feedback on problems and bugs encountered with the software as well as suggestions for changes or new features. Although it may not be possible to implement every suggested new feature, we will try to help users solve problems with the software and will use their inputs to make the documentation clearer and more complete over time. Questions and comments about the photoclinometry software and its documentation should be addressed to Randy Kirk [rkirk@usgs.gov].

Problems with obtaining or installing the ISIS software should be addressed to ISIS Support Center.

Problems and suggestions concerning this web page should be addressed to Mark Rosiek [mrosiek@usgs.gov].

Credits

This material is based upon work supported by the National Aeronautics and Space Administration under Contract No. W 10,185 issued through the Office of Space Science.

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