Level 2 Help for MARSXYZ

INP

Two files containing the input stereo pair images.  The pixel data from these
files are not used; only the label information is used to determine the
pointing and camera models.

A single file list file may also be specified (a la marsmos, etc.), but the
file list must have only two entries.

Note that there's no actual requirement that the first input be left or the
second right.  The two images can be given in any order.  The first image,
though, is the "master" image; the disparity maps and output files match the
first image's pixels.  Convention places left first, however.


OUT

Output files containing the XYZ coordinates.

If three filenames are given, three separate 1-band files will be created,
one each for X, Y, and Z.  If only one filename is given, a single 3-band
file will be created, with bands in (X,Y,Z) order.

The output files are in REAL (float) format.


DISPAR

REAL-formatted images giving the line and sample disparity.  Either
two files may be given (line, sample order), or a single file with two bands.

The disparities are interpreted as follows:  Each pixel in the disparity
map corresponds to the same pixel in the first (left) input.  The value of
the pixel in the disparity map is the line and sample of the point in the
second (right) image, which matches this location in the first (left).  Note
that these are standard VICAR 1-based file coordinates.  If both line and
sample disparity values are 0, the point has no value.


ERR_FILE

A REAL-formatted output file containing the view ray miss distance, in
meters.  This file is not required and will not be generated if ERR_FILE
is not specified.


NAVTABLE

Corrected navigation filename.
If marsnav was run on the input images it created a table of corrected
pointing parameters. If you refer to this table using NAVTABLE it
will override the pointing parameters (e.g. azimuth and elevation) in the
picture labels, giving different (and presumably better) output coordinates.


ERROR

Maximum permitted view ray miss distance per meter of range.
Any two projected view rays through a pixel will miss by some value M meters.
If M divided by the range to that pixel (in meters) exceeds  
ERROR the point will be rejected.
Default is .0025 (or 2.5 millimeter per meter).


ABSERROR

Maximum permitted view ray miss distance in absolute terms (not adjusted for
range).  Any two projected view rays through a pixel will miss by some value
M meters.  If M exceeds ABSERROR the point will be rejected.

Note that the absolute error should not be larger than the camera baseline
(distance between the cameras); that would indicate a divergent ray.  The
value should be somewhat less than that, although testing with MER data
shows a .05 is a good cutoff regardless of baseline.

Default is .05 (or 0.5 centimeters).


LINEDISP

Maximum permitted line disparity. If the line values of a tiepoint
differ by over LINEDISP pixels then the point will be rejected.
Default is 2.5 pixels. Accuracy depends upon the camera models themselves
so tolerances cannot be set too small.


AVGLINEDISP

Maximum permitted line disparity from local average.

If enabled, a delta line disparity image is created internally (delta line
disparity meaning the line disparity from the file minus the line number -
most people think of this as the true disparity).

If any line disparities exceed LINEDISP, they are discarded.  For all
remaining pixels, a box filter is run over the line disparity image
(see BOX_WIDTH, BOX_HEIGHT) to compute the average line disparity in the
local area around each pixel.  The line disparity is then compared to this
average.  If the difference exceeds AVGLINEDISP, the pixel is rejected.

The effect of this is to adapt to camera models that are not precisely
epipolar aligned.  The line disparities can "drift" while still preserving
a very tight tolerance on the line disparities (which helps to reject noise).

Recommended values are 0.5 for AVGLINEDISP, 4.0 for LINEDISP, and 51 for
BOX_WIDTH and BOX_HEIGHT.

A negative value for AVGLINEDISP turns off the check and disables the box
filter.


BOX_WIDTH

Width of the box filter used by AVGLINEDISP.  Must be odd.


BOX_HEIGHT

Height of the box filter used by AVGLINEDISP.  Must be odd.


ZLIMITS

Two values representing the lowest and the highest values of Z permitted.
Values of Z outside this range will be rejected.
Defaults to (-10,+10) meters.


RANGE_LIMIT

Override for the range limit.  If this parameter is specified, RANGE_FACTOR
is ignored.

The range limit is the maximum distance from the reference (left) camera
that an XYZ point can have.  Any points farther than this are rejected,
since range accuracy diminishes to the point of uselessness beyond a certain
point, as the view rays become more and more parallel.


RANGE_FACTOR

This is the normal way to specify the range limit.  This is a factor that
is multiplied by the camera baseline (distance between the two cameras)
in order to derive the range limit.

The range limit is the maximum distance from the reference (left) camera
that an XYZ point can have.  Any points farther than this are rejected,
since range accuracy diminishes to the point of uselessness beyond a certain
point, as the view rays become more and more parallel.


SPIKE

Enables the spike filter, and specifies an absolute threshold.

The spike filter works by computing the average XYZ value of all pixels
within a box surrounding the pixel in question (see SPIKE_BOX).  A distance
is then computed from the pixel to the average in XYZ space.  If this distance
is greather than the SPIKE threshold, then the pixel is considered a "spike"
(something unlikely to happen in a real scene) and is rejected.

Note that all average XYZ values are computed at once, before anything is
rejected by the spike filter.  Therefore, rejecting one spike will not affect
a neighbor's computation.

Spikes seem to occur as a result of the marscor3 algorithm, but the detailed
reason for them is not known.

If SPIKE and SPIKE_RANGE are not specified, no spike filtering is done.

Recommended value:  none (use SPIKE_RANGE instead)


SPIKE_RANGE

Enables the spike filter (see SPIKE).  However, instead of using a constant
threshold, the spike threshold is adjusted based on range from the camera
(via spike_range * range).  So, the farther away the point is, the larger the
allowable spike.  This compensates for increasing noise as you go farther away
from the camera.

Note that it is okay to have both SPIKE and SPIKE_RANGE active at the same
time.  One average is computed, then the distance is compared to both
thresholds.

Recommended value:  0.04


SPIKE_BOX

Specifies the size of the box used to compute the average XYZ for the spike
filter.  If one value is specified, the result is a square box.  If two are
specified, a rectangular box of (height, width) is used.

Note that both height and width of the box must be odd.


OUTLIER

This filter attempts to remove "outliers", defined as pixels with too few
computed neighbors.

The theory is that pixels should have neighbors, because the scene is generally
continuous.  Having too few neighboring good pixels is thus likely the result
of a bad correlation.

Neighbors are defined as any pixel within a box (see OUTLIER_BOX) that has a
valid result.  A binary image is defined, such that missing pixels are 0 and
valid pixels are 1.  A box filter is then run over this image.  If the result
of this box filter is less than the OUTLIER threshold, the pixel is rejected.

If OUTLIER is set to 0.5, this has the same effect as running a median filter,
which is where this idea originated.

If OUTLIER is greater than 0.5, the effect is to erode away the edges of the
valid area.  At 0.5, the "average" edge is retained, while removing those
pixels beyond the edge (which still might be connected to the valid area).
Below 0.5, the effect tends more towards removing only more isolated pixels.
Thus, a value of 1.0 is maximum filtering (only pixels with the entire box
filled will be retained - not recommended) and 0.0 effectively disables the
filter.

Note that this is NOT the same as a "blob" filter.  It does not look at
connectedness in the sense of disparities being close to each other.  It
only looks at how many valid neighbors there are.

This is the last filter, thus valid neighbors have already passed all the
other tests.

Recommended value:  0.5


OUTLIER_BOX

Specifies the size of the box used to compute the outlier filter.  If one
value is specified, the result is a square box.  If two are specified, a
rectangular box of (height, width) is used.

Note that both height and width of the box must be odd.


WRITE_CM

If specified, the program will write an updated camera model to the output
file.  This camera model is for the left image, as modified by the nav file.
The purpose of this is to be able to create a properly-labeled XYZ file
from unmodified FFL (linearized) files and a nav file, for the purpose of
pointing-correction of a mesh.

Note that point=cm=label should NOT be specified, as that will override the
nav file.  Also, you may need to specify point=cahv_fohv=xxx (often, "max"),
in order for the camera model to match the FFL.  Basically, whatever is given
to marscahv, should be given in this case as well.


CONFIG_PATH

A colon-separated list of directories in which to look for configuration
and calibration files.  Environment variables are allowed in the list
(and may themselves contain colon-separated lists).  The directories are
searched in order for each config/cal file when it is loaded.  This allows
multiple projectes to be supported simultaneously, and allows the user to
override any given config/cal file.  Note that the directory structure below
the directories specified in this path must match what the project expects.
For example, Mars 98 expects flat fields to be in a subdirectory named
"flat_fields" while Mars Pathfinder expects them to be directly in the
directory specified by the path (i.e. no intermediate subdirectories).


MATCH_METHOD

Specifies a method for pointing corrections.

Loose method matchs with pointing parameters of the image.
Tight method matchs with unique id of the image.


MATCH_TOL

Tolerance value for matching pointing parameters in the pointing corrections file.
Used if MATCH_METHOD=LOOSE
Default value is pretty arbitrary, though seems to work well so far....


POINT_METHOD

Specifies a mission-specific pointing method to use.  Normally this
parameter is not used, in which case the "default" pointing methods
are used.  Some missions may have special, or alternate, pointing
methods available, which are indicated by this string (for example,
backlash models, using arm joint angles instead of x/y/z/az/el, etc).
A substring search is used, so multiple methods (where that makes sense)
can be specified by separating the keywords with commas.

Note that nav files created using one pointing method will most likely
not be compatible with a mosaic created using a different pointing method.

The methods available vary per mission, but some methods available at
the time of this writing are:

BACKLASH : Mars 98 SSI only.  Selects a backlash pointing model,
which adjusts the telemetered azimuth and elevation values based on
knowledge of the camera's mechanical backlash and the direction the
motor was travelling when the image was taken.


DATA_SET_NAME

The DATA_SET_NAME typically identifies the instrument that acquired the
data, the target of that instrument, and the processing level of the data.
This value is copied to the output label, property IDENTIFICATION,
keyword DATA_SET_NAME.


DATA_SET_ID

The DATA_SET_ID value for a given data set or product is constructed
according to flight project naming conventions.  In most cases the
DATA_SET_ID is an abbreviation of the DATA_SET_NAME.
This value is copied to the output label, property IDENTIFICATION,
keyword DATA_SET_ID.


RELEASE_ID

When a data set is released incrementally, such as every three months during
a mission, the RELEASE_ID is updated each time part of the data set is released.
For each mission(or host id if multiple spacecrafts), the first release of a data
set should have a value of "0001".
This value is copied to the output label, property IDENTIFICATION,
keyword RELEASE_ID.


PRODUCT_ID

Specifies a permanent, unique identifier assigned to a data product by
its producer. Most commonly, it is the filename minus the extension.
This value is copied to the output label, property IDENTIFICATION,
keyword PRODUCT_ID.


PRODUCER_ID

Specifies the unique identifier of an entity associated with the
production of a data set. This value is copied to the output label,
property IDENTIFICATION, keyword PRODUCER_ID.


PRODUCER_INST

Specifies the identity of a university, research center, NASA center or other
institution associated with the production of a data set.
This value is copied to the output label, property IDENTIFICATION, keyword
PRODUCER_INSTITUTION_NAME.


TARGET_NAME

Specifies a target.  The target may be a planet, satelite, ring, region, feature,
asteroid or comet.  This value is copied to the output label, property
IDENTIFICATION, keyword TARGET_NAME.


TARGET_TYPE

Specifies the type of a named target. This value is copied to the output
label, property IDENTIFICATION, keyword TARGET_NAME.


RSF

Rover State File.  This is a list of filenames to load containing
Rover State information.  These files contain position and orientation
information for a rover (or other mobile spacecraft) at various sites.
They are in XML format.  See the "Rover Motion Counter (RMC) Master File SIS"
for details on these files.

Rover State Files have a priority order.  The files listed first have
the highest priority.

Environment variables may be used in the list.

For MER, if a directory is specified, then that directory is searched for
RMC Master files and any found are loaded.  The directory structure and
filename convention is covered in the RMC SIS.  The directory specified
is the one containing "master", so if <dir> is the name specified in the
RSF parameter, the following files will be searched for:

<dir>/master/_Master.svf
<dir>/master/_Site__Master.rvf

The name of each file loaded is printed to the stdout log for reference.


DEBUG_RSF

If enabled, this causes the internal database of RMC locations to be
printed out to the stdout log.  This is after the RSF files have been
loaded and the coordinate systems read from the input label(s).


COORD

The coordinate system to use for all input parameters and output values,
and the XYZ points themselves.  The interpretation of the values is dependent
on the mission.  Some representative missions are listed here:

Fixed - The Fixed frame (default).  This is the ultimate reference frame
    (see also FIXED_SITE for rover missions).
Instrument - The "natural" frame for the instrument (of the first input
    image).  MPF: Lander or Rover; M98: MVACS; MER: Rover.
Site - A major Site frame.  For rover missions, COORD_INDEX specifies which
    Site frame to use.  Non-rover missions treat this as Fixed.
Rover - An instance of the Rover frame.  For rover missions, COORD_INDEX
    specifies which instance of the rover frame to use.  Non-rover mission
    use the spacecraft frame (e.g. Lander for M98).  For MSL, this is the
    Rover Nav frame.
Local_Level - An instance of a Local Level frame.  This is typically
    coincident with the Rover frame (in XYZ) but oriented toward North
    like the Site and Fixed frames.  For MER, this is an instance of a
    Drive index move.
RMECH - For MSL, this is the Rover Mechanical frame.  It should not normally
    be used except for testing.


COORD_INDEX

The index specifies which instance of a coordinate system to use.  It is
currently applicable only to rover-based missions, but could have other
uses.  The index is equivalent to the Rover Motion Counter (RMC) for MER
and FIDO.

For MER/FIDO, there are many Site frames.  Each is numbered with a single
index.  For Site Frames, coord_index specifies which to use.  Likewise,
there are many Local_Level and Rover frames, corresponding to values of
the RMC.  The multiple instances of this frame are selected by COORD_INDEX.

Generally COORD_INDEX defaults sensibly so you don't usually need to
specify it.  It will default to the instance used by the first input.


FIXED_SITE

Specifies which major Site is the "Fixed" Site for this run.

Historically, MPF and M98 had a single "Surface Fixed" frame which never
moved, and which all other coordinate system frames were referenced to.
With the advent of long-range rovers (such as MER and FIDO), that became
insufficient.  The rover traverses far enough that errors in knowledge of
coordinate system offset and orientation become unacceptable.

For this reason, a system of major Sites was introduced.  Periodically
during the mission, a Site frame is declared.  This then becomes the
reference frame for all activities until the next Site is declared.
References are kept local, and errors don't propogate across Sites.

However, if images from more than one Site are combined together, the
Site's must be placed relative to each other.  Therefore a single reference
frame is still needed to combine different sites.

The FIXED_SITE parameter controls which of the major Site frames is
the reference ("fixed") site for this program run.  This fixed frame
can vary in different program runs, but is constant throughout one
execution.

If not specified, FIXED_SITE defaults to the minimum Site number (i.e.
lowest numbered, or earliest chronologically) used in all input images.
Normally this default is sufficient; rarely must FIXED_SITE be specified.

One or more Rover State Files must usually be specified in order to combine
image from more than one Site.  These describe the relationship between
sites.  See the RSF parameter.


SOLUTION_ID

Specifies which solution ID to use when specifying the coordinate system.

There are potentially many different definitions for the same coordinate
system.  These are identified via a unique Solution ID.  If this parameter
is given, only the specified solution's definition is searched for.  Without
it, the "best" available solution is chosen.

It is extremely rare that this parameter should be needed.  The default
will be sufficient in almost every case.

Note that the current MER implementation requires that a value for COORD_INDEX
also be provided, in order for this parameter to take effect.