Private parameters for program NGCALC
Overview of NGCALC's parameter interface.
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NGCALC's cut-extract interface.
FIGURE
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See figure for the overall interface.
NGCALC's header/data display interface.
FIGURE
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See figure for the overall interface.
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: type of action |
Expected input: Character *24: 1 value
Specify the action to be performed:
Creating cuts from external data:
EXTRACT extract information from SCN file into cuts
COPY copy cuts to other NGF file, retaining their indices
(this action is mainly useful for discarding cuts no longer
needed and thereby freeing disk space)
Viewing the contents of the .NGF file:
SHOW show information in cut headers and data
BRIEF show summary per group/field showing numbers of polarisations,
interferometers, cuts and data points
Calculations:
CALC Perform one of a set of predefined algorithms on individual cuts
MERGE Merge a number of cuts into a single new cut.
NOTE: Overlapping points will be averaged so you may use MERGE
to average e.g. a set of interferometers with data points
at coincident hour angles.
COMBINE Combine cut(s) in user-specified expression
Sorting:
Starting from a cut in the HA direction, these actions produce a new cut
in the frequency or baseline direction for each hour angle present in any of
the input cuts. Use the HA_RANGE parameter to limit the number of output cuts.
The output cuts are in a primitive format in which the data are transposed
but NOT the coordinate axes. These wrong axes appear in plots of the transposed
cuts and must be interpreted as indicated below. In calculations, however,
coordinates will be interpreted correctly (provided you specify a sensible
calculation).
Transposing a transposed group of cuts reproduces the original cuts. You
may also try to combine TRANS and BASE operations but sensible results are not
guaranteed.
TRANS transpose frequency and HA axes.
In the transposed cuts, each channel is represented by an hour
angle of <channel number>*0.125 deg.
Each hour-angle bin of 0.125 deg is represented by a channel
number, which starts at 0 for the lowest hour angle present.
BASE transpose interferometer and hour-angle axes.
In the transposed cuts, each baseline bin of 10 metres is
represented by an HA bin of .125 deg at HA = <baseline>/10*.125
deg; baselines landing in the same bin are averaged.
Each hour-angle bin of .125 deg is represented by a baseline
sequence number of HA*.125.
Plotting:
MONGO output cut data in a MONGO-readable file
PLOT plot data in NGF cut(s)
Miscellaneous:
DELETE delete cuts. (Only the index linkage is removed but the cut data
remain in the file: Use COPY to free the file space.)
BEWARE: This action is IRREVERSIBLE.
NODE switch to other NGF file
QUIT terminate NGCALC
Data-format conversions:
CVX convert NGF file from other machine's format to local format
NVS update to latest NGF-file format
Prompt: Baseline range (metres)
Expected input: Real: 1 to 2 values
Enter the the lower and upper ends of baseline range to plot.
Prompt: Baseline plot scale (metres/cm)
Expected input: Real: 1 value
Prompt: calculation type
Expected input: Character *24: 1 value
Specify the action to be performed on individual cut(s).
AVER average cut and report results
The following actions will create a new cut for each input cut with the same
index numbers except for a new SEQ number.
SMOOTH create new cut(s) by smoothing cut data with a triangular
function (whose halfwidth you will specify)
POLY fit N+1 coefficients of an Nth-order polynomial
P= c0 +c1*HA +c2*HA**2 +... +cN*HA**N
through cut data and create new cut(s) from the residuals
CPOLY as POLY, but fitting only N selected coefficients of an
Mth-order polynomial. M>N; the missing coefficients are held
at 0. (This method can be used, e.g., to fit a polynomial for
which you know a priori that it must be even.)
DPOLY subtract values of a polynomial (yet to be specified) from cut
data and create new cut(s) from the results
SHIFT create new cuts with visibility values transformed to a
different sky position
NULL create new cuts with data points in an HA range (yet to be
selected) deleted
QUIT leave CALC
Note: All calculations are done with complex numbers. To use e.g. only
amplitude, convert it first with an expression= AMPL(#..) in
a COMBINE action.
Prompt: data representation
Expected input: Character *24: 1 value
Specify action to perform:
SHOW show detailed cut data
AMPL show amplitude of cut data
PHASE show phase of cut data
QUIT quit data part
Prompt: expression
Expected input: Character *80: 1 value
Specify the expression defining the new output cut. It is safest to enclose the expression in double quotes.
Each data point in the output cut will be set to the value of your expression, using the values of the corresponding data point in each of the input cuts in the expression. Elements of an expression can be:
References to input cuts of the form #<number> or ##<number> (see NOTE
below). You will be prompted later to identify one cut to be associated
with each of the numbers you use in the expression. For each output
point, a reference refers to the input point at the same hour angle.
Real constants, e.g. 5, -1.23E-12
Symbolic constants
PI [=3.14..], EE [=2.71..], CC [=light velocity in km/s],
DRAD [=180/PI]
Standard functions of real or complex argument (angles always in
degrees):
SIN(x), COS(x), ASIN(x), ACOS(x), ATAN(x), ATAN(real,imag)
EXP(x), EXP10(x), EXP2(x), LOG(x), LOG10(x), LOG2(x)
ABS(X), SQRT(X(
REAL(x), IMAG(x), AMPL(x), PHASE(x), IMUL(x) (mmultiply x by i)
Standard functions of a real argument that will be performed separately
on the real and imaginary components of a complex argument
FLOOR(x), CEIL(x), ROUND(x), INT(x), FRACT(x)
Cut-data-point coordinates:
RA [right-ascension], DEC [declination], HA [hour-angle],
UT [univ.time], FQ [freq. in MHz], BL [baseline in m],
UU [U in lambda], VV [V in lambda]
Operators, in order of decreasing priority (results of logical and
relation expressions are 0. (False) or 1. (True)):
unary +,-
**,^ (power)
*, /, +, -
>=,<=,=,<,>,<> (comparisons: if either value to be compared is
complex, absolute values are used in the comparison)
<> (not) & (and) (or)
Example:
#1*(REAL(#1)<0)+#2*(REAL(#2)>0): for each hour angle, take the data
value from cut #1 if it is <0 and the data value from cut #2 if
it is >0, and add them to get the data point at the same hour
angle in the output cut
NOTE:
You may loop over sectors in the standard way. Each of the input
sectors in the expression will be incremented at the start of a new loop cycle.
You may, however, inhibit this incrementing by using a double '#', e.g. ##2.
Prompt: data type
Expected input: Character *24: 1 value
Specify the type of data to extract:
DATA Observed visibilities
WEIGHT Visibility weights
MODEL Model visibilities
TCOR Telescope gain/phase corrections
ICOR Interferometer gain/phase corrections
IFDATA 'IF' data: gain/system-temperature parameters from the WSRT
on-line system; you will be asked for details later.
QUIT quit EXTRACT action
Prompt: hour-angle plot scale degree/cm
Expected input: Real: 1 value
Prompt: smoothing width
Expected input: Real: 1 value
Specify smoothing halfwidth of triangular smoothing function in degrees of HA.
Prompt: type of IF data
Expected input: Character *8: 1 value
Specify type of 'IF' data to extract:
Quantities related to telescope noise sources:
TPON total-power data for noise source on
TPOFF total-power data for noise source off
TNOISI constant noise source temperature
Quanitities related to telescope system temperatiures:
TSYS system temperatures
TSYSI constant system temperature
Quantities related to interferometer gain correction:
GAIN IF gains
GNCAL gain correction method
RGAINI constant receiver gain
Prompt: max. baseline to include (metres)
Expected input: Real: 1 value
Specify maximum baseline to include in output cut.
Prompt: Mongo file name
Expected input: Character *80: 1 value
Specify the name of the file to be used in Mongo plotting.
Prompt: Input[+output] 'node' name
Expected input: Character *80: 1 value
This is the file from which input cuts will be read.
Except in COPY operations, it is also the file to which new cuts will be written.
Enter ** (or e.g. /user0/mydata/**) to get a list of files, then enter #<n> to select the <n>-th file from such that list.
Prompt: plot offset (data units)
Expected input: Real: 1 value
Example:
If you enter 100, <data values>-100 will be plotted.
Prompt: Output 'node' name
Expected input: Character *80: 1 value
This is the file to which cuts will be copied. The source and output files MUST be different.
Enter ** (or e.g. /user0/mydata/**) to get a list of files, enter #nn to select the nn-th file from such a list.
Prompt: cut-data component
Expected input: Character *24: 1 value
Specify the data component for the output cut:
COS real part
SIN imaginary part
AMPL ABS(data)
PHASE ARG(data)
Prompt: polynomial coefficients
Expected input: Real: 1 to 11 values
Specify the coefficients of the polynomial to be subtracted:
P= c0 +c1*HA +c2*(HA**2) +... +cN*(HA**N)
Prompt: number of coefficients to fit
Expected input: Integer: 1 value
Specify number of coefficients of the polynomial to be fitted to the data.
For CALC=POLY, this is 1 + the polynomial's degree.
For CALC=DPOLY it is the number of non-zero coefficients. You will be prompted later for there orders.
Prompt: orders of coefficients to fit
Expected input: Integer: 1 to 11 values
Specify the orders of the polynomial coefficients to fit to. Default is 0,...,<N>, where <N> is the number you gave for POLY_N.
Example:
To fit a 6th-degree even polynomial, specify POLY_N=3 and POLY_USE=0,2,4,6.
Prompt: plot scale (data units/mm)
Expected input: Real: 1 value
Specify the scale in units/mm.
Prompt: Sector-header action |
Expected input: Character *24: 1 value
Specify interaction with this sector header:
Show details of the sector header:
SHOW show entire sector header
EDIT edit fields (values) in the Sector header by name
Navigation:
NEXT: proceed to the header for the next sector selected
CONT: descend into the scans of this sector
QUIT: return to the file-header level
Prompt: polarisation(s)
Expected input: Character *4: 1 value
Select the polarisation(s) to be used. Your answer will be interpreted according to the data type you will select hereafter
Interferometer Telescope
============== =========
XYX XX, YX, YX and YY X and Y
XY XX and YY X and Y
X XX only X only
Y YY only Y only
YX XY and YX none
YYX YX none
XXY XY none
Prompt: l,m shifts to apply to data (arcsec)
Expected input: Real: 1 to 2 values
Specify the l,m shifts in arcsec to be applied to data
Prompt: Cut to use
Expected input: Character *32: 1 value
Define the cut represented by each of the variables of the form #<n> and ##<n> in your expression. You are being prompted for each such variable that is present in the expression. Your reply must designate ONE cut.
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