Private parameters for program NMODEL
This document contains an overview of the parameter interface of the program NMODEL. The program also uses a number of public interfaces; references to these are also listed. show parameters that The remainder of the document describes the individual parameters in alphabetical order. This description centers on the Help texts, which have been designed to guide the user to the proper choice at each junction, even if his knowledge of the overall workings of the program is only superficial.
See also:
Prompt: Action
Expected input: Character *24: 1 value
Specify action to perform:
General:
HELP show some explanation on model lists
HANDLE select general model-handling branch
Model construction:
FIND find sources in map (.WMP file)
UPDATE update sources by comparison with visibilities (.SCN file)
Transfer of model to/from .SCN file:
SAVE save model data in .SCN file
GET get model from .SCN file
Wholescale conversions of model list:
CONVERT Convert model list from epoch to epoch or coordinate to
coordinate with conversion of l,m coordinates and intensities
if necessary
EDIT Change model-list overall parameters without conversion of
coordinates and intensity (except possible field rotation if
converting from apparant <-> epoch)
REDIT Change reference coordinates and frequency. Intensities will
be corrected for spectral index only.
FEDIT As REDIT, but intensities will also be corrected for the
effect of different beams at different frequencies
BEAM Correct sources for attenuation by primary beam
DEBEAM Apply primary-beam attenuation to sources
Utilities:
FROM_OLD convert old format source list (use B1950 or Apparent by
preference)
TO_OLD convert to old format source list
NVS make new version of model file if necessary
CVXL convert formats between machines
QUIT finish
Prompt: Map area: l,m, dl,dm
Expected input: Integer: 1 to 4 values
Specify the map area to be selected:
l, m position in grid spacings of centre of area
0,0 is the map centre, increaing toward the upper right (i.e.
with DEcreasing RA and INcreasing DEC)
dl, dm horizontal and vertical area sizes
Prompt: List of sources or *
Expected input: Integer: 1 to 128 values
Specify up to 128 numbers of sources in the model list that you want to use as calibrators.
Prompt: Target coordinate system
Expected input: Character *24: 1 value
Specify the coordinate system for the output model-list.
If you are CONVERTing, the output model list's coordinates and intensities will reflect the new type, frequency, instrument and central coordinates.
If you are EDITing, the new data will be copied only, but the coordinates will be rotated to the new Pole if you are converting between apparent and epoch.
Prompt: Finding mode
Expected input: Character *24: 1 value
Specify how to select candidate sources:
POS Select sources with highest positive brightness
ABS Select sources with highest absolute brightness
MANUAL Select sources manually with the cursor on a GIDS screen.
Sources are selected by pushing MB1; MB3 will finish;
MB2 will not calculate position, but put grid point as clean
source
Prompt: Select sources on GIDS display (Yes/No)?"
Expected input: Yes/No: 1 value
Specify if you want to point at sources on the GIDS display for the current map
Prompt: Start identification number
Expected input: Integer: 1 value
Specify the start of the ID number to be used in the source list.
Prompt: Lower relative intensity limit
Expected input: Real: 1 value
Specify the lowest limit with respect to the maximum in the map that will be considered a valid source
Prompt: Maximum number of sources to add
Expected input: Integer: 1 value
Specify the maximum number of sources that will be found.
Prompt: old model filename
Expected input: Character *80: 1 value
Specify the filename (includinhg extension) the an old-format RMODEL file to be read or written.
Prompt: RA, DEC, Freq, rot.,instr.
Expected input: DoublePrecision: 1 to 5 values
Specify
RA, DEC (decimal degrees)
precession rotation angle (degrees)
spectral-index reference frequency (MHz)
instrument code (0=WSRT; 1=ATCA)
for the new reference source list position.
Prompt: Reference frequency (MHz)
Expected input: DoublePrecision: 1 value
Specify the spectral index reference frequency (MHz).
Prompt: File name
Expected input: Character *80: 1 value
Specify the node name with the model overall coordinates to use.
Instead of a file name you may reply with a '*'. You will then be prompted for 'manual' inpout of data, unless you are CONVRTing between apparent and epoch coordinates.
Prompt: ONE sector for reference coordinates: grp.obs.fld.chn.seq
Expected input: Character *32: 1 to 64 values
Specify ONE .SCN-file sector from which the reference coordinates (RA, DEC, frequency) are to be taken.
grp.obs.fld.chn.seq = group.obs.field.channel.sequence_number
Prompt: Update cluster size in arcsec (l,m)
Expected input: Real: 1 to 2 values
Specify the cluster size for update in arcsec in the l and m direction.
Prompt: Update type
Expected input: Character *24: 1 value
Specify how the update process should proceed:
SEPARATE each source to be updated is looked at separately,
and they are fiddled to cater for close sources
CLUSTER sources are clustered to bypass closeness problems
COMBINED all sources solved in one go, with sub-clustering
CONSTRAINED use constraints and clustering. The standard
constraint used is to fix all variables for all
but the lowest intensity source
L<type> Loop up to 20 cycles till convergence:
Note that the loop option does not always
work, and is very slow. Preferably use for a
small number of well separated sources/clusters.
Prompt: Update mode
Expected input: Character *24: 1 value
Specify the parameters to be redetermined per source in the update process.
Position and flux:
I Intensity only
LM Position only
ILM Intensity and position
SILM Intensity, spectral index and position (requires a multichannel
observation with <bandwidth per channel>/<frequency> greater
than ..)
Source size:
EXTEND Intensity and size parameters for elliptic-Gaussian model
(major/minor axes, position angle)
Source polarisation:
QUV Stokes Q/I, U/I, V/I
PESTIM Estimate the total linear polarisation, and store it as Stokes
Q. NOTE that this improper use of the model list is not
recorded, so you it is your responsibility to interpret this
kluge correctly.
NOTES:
1. All sources in the model are taken into account in determining the
residual visibilities on which the update fit is performed. However, no updates
are attempted for sources of type other than 0 nor for CLEAN components.
If you want to protect one or more sources from being updated, you can
do so by temporarily changing their type (OPTION=MODIFY, MODIFY_OPTION=FEDIT,
see the Help text there).
2. It is recommended that you use a set of interferometers that gives a
uniform baseline coverage, e.g. by selecting fixed-movable (FM) interferometers
only.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.