Provided by: fitsh_0.9.2-1_amd64 
NAME
grmatch - pairing lines by involving identifier or cross matching
SYNOPSIS
grmatch [options] -r <reference> -i <input> [-o <output>]
DESCRIPTION
The program `grmatch` matches lines read from two input files, namely from a reference and from an input
file. All implemented algorithms are symmetric, in the manner that the result should be the same if these
two files are swapped. The only case when the order of these files is important is when a geometrical
transformation is also returned (see point matching below), in this case the swapping of the files
results the inverse form of the original transformation. The lines (rows) can be matched using various
criteria. 1. Lines can be matched by identifier, where the identifier can be any concatenation of
arbitrary, space-separated columns found in the files. Generally, the identifier is represented by a
single column (e.g. it is an astronomical catalog identifier). The behaviour of the program can be tuned
for the cases when there are more than one rows with the same identifier. 2. Lines can be matched using a
2-dimensional point matchig algorithm. In this method, the program expects two-two columns both from the
reference and input files which can be treated as X and Y coordinates. If both point lists are known, the
program tries to find the appropriate geometrical transformation which transforms the points from the
frame of the reference list to the frame of the input list and, simultaneously, tries to find as many
pairs as possible. The parameters of the geometrical transformation and the whole algorithm can be
fine-tuned. 3. Lines can be matched using arbitrary- (N-) dimensional coordinate matching algorithm. This
method expects N-N columns both from the reference and input files which can be treated as X_1, ..., X_N
Cartesian coordinates and the method assumes both of the point sets in the same reference frame. The
point 'A' from the reference list and the point 'P' from the input list forms a pair if the closest
point to 'A' from the input list is 'P' and vice versa.
OPTIONS
General options:
-h, --help
Give general summary about the command line options.
--long-help, --help-long
Gives a detailed list of command line options.
--wiki-help, --help-wiki, --mediawiki-help, --help-mediawiki
Gives a detailed list of command line options in Mediawiki format.
--version, --version-short, --short-version
Give some version information about the program.
-C, --comment
Comment the output (both the transformation file and the match file).
Options for input/output specifications:
-r <referencefile>, --input-reference <referencefile>
Mandatory, name of the reference file.
<inputfile>, -i <inputile>, --input <inputfile>
Name of the input file. If this switch is omitted, the input isread from stdin (specifying some
input is mandatory).
-o <output>, --output <output>, --output-matched <output>
Name of the output file, containing the matched lines. The matched lines are pasted lines, the
first part is from the reference file and the second part is from the input file, these two parts
are concatenated by a TAB character. This switch is optional, if it is not specified, no such
output will be generated.
--output-excluded-reference <out>, --output-excluded-input <out>
Names of the files which contain the valid but excluded lines from the reference and from the
input. These outputs are disjoint from the previous output and altogether contaions all valid
lines.
--output-id <out>
Name of the file which contaions only the identifiers of the matched lines. If the primary
matching method was not identifier matching, one should specify the column indices of the
identifiers by --col-ref-id and --col-inp-id also.
--output-transformation <output-transformation-file>
Name of the output file containing the geometrical transformation, in human-readable format, if
the matching method was point matching (in other case, this option has no effect). The
commented version of this file includes some statistics about the matching (the total number
of lines used and matched, the required CPU time, the final triangulation level, the fit
residuals and other things like these).
In all of the above input/output file specifications, the replacement of the file name by "-" (a
single minus sign) forces the reading from stdin or writing to stdout. Note that all parts of the any
line after "#" (hashmark) are treated as a comment, therefore ignored.
General options for point matching:
--match-points
This switch forces the usage of the point matching method. By default, this method is assumed
to be used, therefore this switch can be omitted.
--col-ref <x>,<y>, --col-inp <x>,<y>
The column indices containing the X and Y coordinates, for the reference and for the input file,
respectively. The index of the first column is always 1, the index of the second is 2 and so
on. Lines in which these columns do not contain valid real numbers bers are omitted.
-a <order>, --order <order>
This switch specifies the polynomial order of the resulted geometrical transformation. It can be
arbitrary positive integer. Note that if the order is A, at least (A+1)*(A+2)/2 valid points are
needed both from the reference and both from the input file to fit the transformation.
--max-distance <maxdist>
The maximal accepted distance between the matched points in the coordinate frame of the input
coordinate list (and not in the coordinate frame of the reference coordinate list). Possible pairs
(which are valid pairs due to the symmetric coordinate matching algorihms) are excluded if
their Eucledian distance is larger than maxdist. Note that this option has no initial value,
therefore, if omitted, all possible pairs due to the symmetric matching are resulted, which, in
certain cases in practice, can result unexpected behaviour. One should always specify a
reasonable maximal distance which can be estimated only by the knowledge of the physics of
the input files.
See more options concerning to point matching in the section "Fine-Tuning of Point Matching"
below. That section also describes the tuning of the triangulation used by the point matching
algorithm. For a more detailed description about the point matching algorithms based on pattern and
triangle matching see [1], [2] or [3].
General options for coordinate matching:
--match-coord, --match-coords
This switch forces the usage of the coordinate matching method. Note that because of the common
options with the point matching method, one should specify this switch to force the usage of the
coordinate matching method (the default method is point matching, see above).
--col-ref <x>[,<y>,[<z>...]] --col-inp <x>[,<y>,[<z>...]]
The column indices containing the spatial coordinates, for the reference and for the input file,
respectively. The index of the first column is always 1, the index of the second is 2 and so
on. Lines in which these columns do not contain valid real numbers are omitted. Note that the
dimension of the coordinate matching space is specified indirectly, by the number of column
indices listed here. Because of this, the number of column indices should be the same for
the reference and input, in other case, when the dimensions are mismatched, the program exits
unsuccessfully.
--max-distance <maxdist>
The maximal accepted distance between the matched points. Possible pairs (which are valid pairs
due to the symmetric coordinate matching algorihms) are excluded if their Eucledian distance is
larger than maxdist. Note that this option has no initial value, therefore, if omitted, all
possible pairs due to the symmetric matching are resulted (see also point matching, above).
General options for identifier matching:
--match-id, --match-identifiers
This switch forces the usage of the identifier matching method.
--col-ref-id <i>[,<j>,[<k>...]] --col-inp-id <i>[,<j>,[<k>...]]
Column index or indices containing the identifiers, from the reference and from the input
file, respectively.
--no-ambiguity, --first-ambiguity, --any-ambiguity, --full-ambiguity
These options tune the behaviour of the matching when there is more than one occurrence of a
given identifier in the reference and/or input file. If --no-ambiguity is specified, these
identifiers are discarded, this is the default method. If --first-ambiguity is specified, only
the first occurence is treated as a matched line, independently from the number of occurrences.
If the switch --any-ambiguity is specified, the lines are paired sequentally, until there is any
left from the reference and from the input. For example, if there is 4 occurrences in the
reference and 6 in the input file of a given identifier, 4 matched pairs are returned.
Otherwise, if --full-ambiguity is specified, all possible combinations of the lines are
treated as matched lines. For example, if there is 4 occurrences in the reference and 6 in
the input file of a given identifier, all 4*6=24 combinations are returned as matched pairs.
Fine-tuning of point matching:
--triangulation <parameters>
This switch is followed by comma-separated directives, which specify the parameters of the
triangulation-based point matching algorithm:
delaunay, level=<level>, full, auto, unitarity=<U>
These directives specify the triangulation level used for point matching. "delaunay" forces the
usage only of the Delaunay-triangles. This is the fastest method, however, it is only working if
the points in the reference and input lists are almost competely overlapping and describe
almost the same point sets (within a ratio of common points above 60-70%). The "level"
specifies the level of the expansion of the Delaunay-triangulation (see [1] for more details).
In practice, the lower the ratio of common points and/or the ratio of the overlapping, the
higher level should be used. Specifying "level=1" or "level=2" gives a robust but still
fast method for general usage. The directive "full" forces full triangulation. This can be
overwhelmingly slow and annoying and requires tons of memory if there are more than 40-50
points (the amounts of these resources are proportional to the 6th(!) and 3rd power of the
number of the points, respectively). The directive "auto" increases the level of the
triangulation expansion automatically until a proper match is found. A match is considered as a
good match if the unitarity of the transformation is less than the unitarity U specified by the
"unitarity=U" directive (see also the section Notes/Unitarity below).
mixed, conformable, reverse
These directives define the chirality of the triangle spaces to be used. Practically, it means
the following. If we don't know whether the input and reference lists are inverted respecting to
each other, one should use "mixed" triangle space. If we are sure about that the input and
reference lists are not inverted, we can use "conformable" triangle space. If we know that the
input and reference lists are inverted, we can use "reverse" space. Note that although
"mixed" triangle space can always result a good match, it is a wise idea to fix the
chirality by specifying "conformable" or "reverse" if we really know that the point sets are
not inverted or inverted respecting to each other. If the chirality is fixed, the program
yields more matched pairs, the appropriate triangulation level can be smaller and in "auto"
mode, the program returns the match definitely faster.
maxnumber=<max>, maxref=<mr>, maxinp=<mi>
These directives specify the maximal number of points which are used for triangulation (for any
type of triangulation). If "maxnumber" is specified, it is equivalent to define "maxref" and
"maxinp" with the same values. Then, the first <mr> points from the reference and the first
<mi> points from the input list are used to generate the triangle sets. The "first" points are
selected using the optional information found in one of the columns, see the following
switches.
(Note that there should be only one --triangulation switch, all desired directives should be written
in the same argument, separated by commas.)
--col-ref-ordering [-]<w>, --col-inp-ordering [-]<w>.
These switches specify one-one column index from the reference and from the input files which
are used to order these lists and select the first "maxref" and "maxinp" points (see above) for
the generation of the two triangle meshes. Both columns should contain valid real numbers,
otherwise the whole(!) line is excluded (not only from sorting but from the whole matching
procedure). If there is no negative sign before the column index, the data are sorted in
descending(!) order, therefore the lines with the lines with the highest(!) values are selected
for triangulation. If there is a negative sign before the index, the data are sorted in
ascending order by these values, therefore the lines with the smallest(!) values are selected
for triangulation. For example, if we want to match star lists, we might want to use only
the brightest ones to generate the triangle sets. If the brightnesses of the stars are specified
by their fluxes, we should not use the negative sign (the list should be sorted in descending
order to select the first few lines as the brightest stars), and if the brightness is known by
the magnitude, we have to use the negative sign.
--fit iterations=<N>,firstrejection=<F>,sigma=<S>
Like --triangulation, this switch is followed by some directives. These directives specify
the number <N> of iterations ("iterations=<N>") for point matching. The "firstrejection"
directive speciy the serial number <F> of the first iteration where points farer than <S>
"sigma" level are excluded in the next iteration. Note that in practice these type of
iteration is really not important (due to, for instance, the limitations of the outliers by the
--max-distance switch), however, some suspicious users can be convinced by such arguments.
--weight reference|input,column=<wi>,[magnitude],[power=<p>]
These directives specify the weights which are used during the fit of the geometrical
transformation. For example, in practice it is useful in the following situation. We try to
match star lists, then the fainter stars are believed to have higher astrometrical errors,
therefore they should have smaller influence in the fit. We can take the weights from the
reference (specify "reference") and from the input (specify "input"), from the column specified
by the weight-index. The weights can be derived from stellar magnitudes, if so, specify
"magnitude" to convert the read values in magnitude to flux. The real weights then is the
"power"th power of the flux. The default value of the "power" is 1, however, for the
maximum-likelihood estimation of an assumed Gaussian distribution, the weights should be the
second power of the fluxes.
Some notes on unitarity. The unitarity of a geometrical transformation measures how it differs from the
closest transformation which is affine and a combination of dilation, rotation and shift. For such a
transformation the unitarity is 0 and if the second-order terms in a transformation distort a such
unitary transformation, the unitarity will have the same magnitude like the magnitude of this
second-order effect. For example, to map a part of a sphere with the size of d degrees will have an
unitarity of 1-cos(d). Therefore, for astrometrical purposes, a reasonable value of the critical
unitarity in "auto" triangulation mode can be estimated as 2 or 3 times 1-cos(d/2) where d is the
size of the field in which astrometry should be performed.
REPORTING BUGS
Report bugs to <apal@szofi.net>, see also http://fitsh.net/.
COPYRIGHT
Copyright © 1996, 2002, 2004-2008, 2010-2015; Pal, Andras <apal@szofi.net>
grmatch 0.9d6 (0.9.2@2016.09.23) September 2016 GRMATCH(1)