ARC-Interactive manual arc line identification

Description:

ARC is a Figaro program that can be used for interactive identif- ication of arc lines.

Each invocation of ARC produces a file arlines.lis in the working directory. This file must be renamed or deleted before re-invoking ARC.

Parameters:

SPECTRUM

The arc data. If there is an X-axis data component the information it contains will be used during the program. At the end of the program the X-axis data component can be set to contain the wavelengths determined by the fit.

ARCTYPE

The type of arc that was used - e.g. HELIUM, NEON, etc. ARC will look for a file called ARCTYPE.ARC which should hold the line list for the arc. Can be up to three types, separated by commas.

SIGMA

Arc line half width in pixels.

ORDER

Polynomial order for 1st fit.

PREVIOUS

If set, ARC will read in the line list from the previous fit as a starting point.

ARFILE

The name of the list file from which the previous fit is to be read. Only used if PREVIOUS is set. Note that the output is always written to ARLINES.LIS. Default extension is .LIS

XCORR

If the previous arc fit was to a different arc, then there is the possibility that the current arc is similar to the previous one but has been shifted. If this is the case, ARC can attempt to determine the shift by cross-correlation of the current arc and the previous one, and can then redetermine the arc line centers by looking for the listed lines at their shifted positions.

OUTPUT

If the final fit obtained is to be used, it is used to reset the x-axis structure in the arc spectrum, giving a new output file. OUTPUT is the name of output file, which can be the same as SPECTRUM, in which case the x-axis structure of SPECTRUM is replaced.

DISNCHAN

Length of displayed sections.

MOVETOX

New plot centre x value.

CMD

At this stage in ARC you have the following options available -

Fit - Repeat the fit. Disp - Display the deviation of the fit from a linear fit. This shows the trend of the fit, and the errors in each line. Order - Change the order of the fit. Edit - Delete or change the wavelength of one or more of the selected lines, without returning to the cursor selection. Reselect - Return to selection using the cursor. Print - Prints a copy of the fit (what ARLINES.LIS would look like if you were to exit now). Auto - Starting from your current fit and arc line list, ARC looks for additional line in the arc at wavelengths given in the line list and adds any it finds to the identified line tables. Xauto - Deletes all the lines found by 'Auto'. Modify - Allows you some control over the Autofit parameters. Quit - Start to exit ARC. Help - (or ?) Display this information.

The first letter of each command is sufficient.

LINENO

Number of line to be edited.

WAVELEN

Wavelength specification.

CHFACT

The autofit algorithm is parameterised as follows.

It takes each pixel in turn. If that pixel is more than CHFACT times the current sigma value from any line already found, it uses that pixel as the starting point for a line search. If anything resembling a line can be found, it calculates its wavelength and looks in the line tables for a line close to that wavelength.

A line is accepted if the discrepancy between calculated and tabulated wavelength is less than SIGFACT times the current RMS value. This means that the criterion for accepting new lines is based on how their wavelength discrepancies compare with those for the lines that have already been accepted.

SIGFACT is the more important parameter.

SIGFACT

The autofit algorithm is parameterised as follows.

It takes each pixel in turn. If that pixel is more than CHFACT times the current sigma value from any line already found, it uses that pixel as the starting point for a line search. If anything resembling a line can be found, it calculates its wavelength and looks in the line tables for a line close to that wavelength.

A line is accepted if the discrepancy between calculated and tabulated wavelength is less than SIGFACT times the current RMS value. This means that the criterion for accepting new lines is based on how their wavelength discrepancies compare with those for the lines that have already been accepted.

SIGFACT is the more important parameter.

WRITEARC

If set, an output spectrum using the arc fit is written.

HARDARC

If set, the output spectrum is plotted in a hard copy.

HARDISP

If set, the dispersion curve is plotted in a hard copy.

QUITSEL

Used to confirm quitting line selection.

LINEOK

Used to confirm a choice of line for deletion, editing etc.

RESOLVE

Used to decide what to do if a line is used twice.

Source comments:

 A R C

 Interactively associates lines in an arc spectrum with
 their wavelengths and performs a fit to these values.

 Command parameters -

 SPECTRUM   The arc data. If there is an x-axis data
            component the information it contains will be
            used during the program.  At the end of the
            program the x-axis data component can be set to
            contain the wavelengths determined by the fit.
 ARCTYPE    The type of arc that was used - e.g. HELIUM,
            NEON, etc.  ARC will look for a file called
            ARCTYPE.ARC which should hold the line list for
            the arc.  Can be up to three types, separated by
            commas.
 ORDER      The initial order for the polynomial fit.
 SIGMA      The initial value for the line width.
 ARFILE     The name of the list file from which the previous
            fit is to be read.  Only used if PREVIOUS is
            set.  Note that the output is always written
            to ARLINES.LIS.  Default extension is .LIS
 OUTPUT     If the final fit obtained is to be used, it is
            used to reset the x-axis structure in the arc spectrum,
            giving a new output file.  OUTPUT is the name of
            output file, which can be the same as SPECTRUM, in
            which case the x-axis structure of SPECTRUM is replaced.

 Command keywords -

 PREVIOUS   If set, ARC will read in the line list from
            the previous fit as a starting point.
 XCORR      If set, and arc is not the same as the arc used
            to generate the previous line list, a shift between the
            two will be determined and the line centers reanalyysed.

 User variables -

 (>) SOFT   (Char) The device/type to be used for graphics
            soft plots.  See the SOFT command for details.
            The device must support a cursor.
 (>) HARD   (Char) The device/type for graphics hard plots.

 Input -

 As named    May use the lines from a previous run.  If so
 by ARFILE   these are read from the previous run's output
             file.  See below.

 Output -

 ARLINES.LIS File containing the lines used in the final fit.
             Format is as follows -
             Number of lines used in fit and file name (I5,23X,A)
             1 blank record, then one header record.
             Then one record for each line, giving channel number,
             wavelength, calculated wavelength and wavelength
             discrepancy line number and auto flag (4F13.4,I7,A4)
             The auto flag is either " (A)" or is a blank string.
             Then one blank record, then a record giving the RMS
             error and the value of SIGMA used (12X,F10.2,19X,F5.2)
             Then one blank record, then one record giving the
             order of fit (i.e. 1 less than number of coefficients)
             (15X,I3), then one blank record, then one or more
             records giving the coefficients (3D23.16)

                                       KS / CIT  13th June 1984