sis_xy

NAME

SYNOPSIS

DESCRIPTION

sis_xy in forward mode: takes as its input USP format trace data and outputs a selected portion of this to stdout in the form of ASCII pairs (essentially a time index followed by the amplitude). Each trace is separated by a blank line. This output may be plotted in x-windows by xgraph. If a previous sis_xy (in reverse mode) was used to create the data set then the line header contains entries to duplicate the first column (X). The trace amplitudes of course produce the second column (Y).

sis_xy in reverse mode: takes as its input a file of X-Y pairs (one pair per line) and converts them to a seismic format trace. If groups of these pairs are separated by a null or blank line they will be considered as separate traces. In that case each group of X-Ys must have identical numbers of entries. Information about the first column (X) is stored in the line header, e.g. first X value and the X increment, assuming regular spacing of the X values. Although this routine can generate multi-trace output without blanks between traces, it cannot handle same on input. Multi-trace input requires blanks between traces to be correctly loaded to individual traces on output. The ascii input may be specified a sparse in which case the output will be amplitudes only at those locations in time specified in the input file.

In forward mode there are two formats of output available: (1) read in each trace, window, then output time-amplitude pairs ending with a null line; (2) read in traces betwee ns,ne, window in time, then write out amplitudes in columns, one per trace.

sis_xy gets both its data and its parameters from command line arguments. These arguments specify the input, output, the trace window, the start and end traces, and verbose printout, if desired.  

Command line arguments

-N ntap

Enter the input data set name or file immediately after typing -N. In forward mode this will be the seismic data set which can be a pipe. In reverse mode if the input is piped then the number of trace samples, the number of traces per record, and the number of records must be specified on the command line. This input file should include the complete path name if the file resides in a different directory. Example -N/b/vsp/dummy tells the program to look for file 'dummy' in directory '/b/vsp'.

-O ntap

Enter the output data set name or file immediately after typing -O. In reverse mode this will be the seismic; in forward mode this is the file of X-Ys. Both may be piped out.

-s ist

Forward mode: enter the start time of the output trace. The default is the beginning of the trace.

-e iend

Forward mode: enter the end time of the output trace. The default is the end of the trace.

-i idec

Forward mode: ehe output sample increment. Default = 1

-ns nstr

Forward mode: enter the start trace number. The default is the first trace of the record.

-ne netr

Forward mode: enter the end trace number. The default is the last trace of the record.

-T0 tdel

Forward mode: ehe output trace increment (can only skip forward - if you need to skip backwards use editt and pipe into sis_xy). Default = 1

-rs nrst

Forward mode: enter start record number. Default value is the first record.

-re nred

Forward mode: enter end record number. Default value is last record.

-R0 rdel

Forward mode: ehe output record increment (can only skip forward - if you need to skip backwards use editt and pipe into sis_xy). Default = 1

-f dels

Forward mode: enter sample interval override. Default is input sample interval.

-b ncomp

Forward mode: basically a different type of display: windowed data for each selected input record are output in ncomp columns (as a function of time which is the first column). ncomp is the number of data columns. This should be a small (<10) value.

-w wvel

Forward mode: do not output any trace values at the top of the trace that are less than this value. Useful for not outputting say the water column of a velocity data set. Default is to output all valid samples.

-B

Forward mode: enter the command line argument '-B' to suppress null lines between traces. xygraph interprets null lines as separators and will then change colors on the plot. Otherwise it will overplot.

-M

Forward mode: enter the command line argument '-M' to read the MBS depth interval line header word and use this as the sample interval.

-R

Enter the command line argument '-R' to invoke the reverse mode, i.e. reading a file of X-Ys and outputting seismic.

-F

Reverse mode option: enter the command line argument '-F' to invoke sparse mode. Here the file contains only the nonzero entries located at the times specified. The user must input a number of output samples and a sample interval.

-nsamp nsamp

Reverse mode: specify the number of samples per trace. If the input XYs are piped then this must be given on the command line; if the input XYs are in a disk file then this entry is an override. This will change the line header but the actual number of non zero samples output will be determined by the input stream, i.e. the number of samples between null lines.

-dt si

Reverse mode: specify the output sample interval (ms or whatever the unitsc value is). The default is the difference between the first pair of times in the input file.

-ntrc ntrc

Reverse mode: specify the number of traces per record. If the input XYs are piped then this must be given on the command line; if the input XYs are in a disk file then this entry is an override. This will change the line header but the actual number of output traces will be determined by the number of traces in the input file.

-nrec nrec

Reverse mode: specify the number of records. If the input XYs are piped then this must be given on the command line; if the input XYs are in a disk file then this entry is an override. This will change the line header but the actual number of output records will be determined by the number of full records of traces in the input file.

-nv nullval

Reverse mode: this is a value that if it occurs in the input will be zeroed on output. Default = 0.0

-SI

Enter the command line argument '-SI' to have the UnitSC line header entry applied to the output sample interval [not used with -R]. In the case of millisecond time data this will result in all output time samples being multiplied by 0.001 so that the output time axis is actually in seconds. Should the input data be depth then of course the output will be meters [or feet]. It is recommended that the user KNOW what the UnitSc value is for their input dataset. Most USP routines expect data in milliseconds so that the default UnitSc value is 0.001 which may not be correct if your data is sampled in something other than milliseconds. You can set this line header entry using the -h0 option of the USP routine utop.

-UnitSc unitsc

Enter the Units Scalar for the -R ASCII dataset being converted to USP format. An entry of 1.0 indicates seconds for time and meters [or feet] for depth. An entry of 0.001 for time would indicate millisecond data. Default = 0.001.

-TmMsFS

Enter the command line argument '-TmMsFS' to have the initial sample unit set to the value of this line header entry. The default is to assume that sample one is time or depth zero.

-V

Enter the command line argument '-V' to get additional printout.

-?

Enter the command line argument '-?' to get online help. The program terminates after the help screen is printed.

Discussion

The output line header from a -R run will have the following header entries completed:

 NumRec = number of records in
 Format = 3
 NumTrc = number of traces in
 SmpInt = delta X between first two samples, or 1, if the calculated delta X is less than unity.
 NumSmp = number of samples in
 MxShDp = maximum value of X axis
 MnShDp = minimum value of X axis
 IntInc = delta X between first two samples
 UnitSc = UnitSc
 DgTrk1 = S
 DgTrk2 = X
           

EXAMPLES

(1) Forward mode

sis_xy -Nseis_in -T04 | xgraph

where every fourth trace of the input seismic data is converted to X-Y pairs and sent to the X-Y plot program. For millisecond data, time is in milliseconds.

sis_xy -Nseis_in -T04 -SI | xgraph

where every fourth trace of the input seismic data is converted to X-Y pairs whose X coordinate has been multiplied by UnitSc and sent to the X-Y plot program. For millisecond data time will now be in seconds.

wind -Nseis_in -s 400 | sis_xy -T04 -SI -TmMsFs | xgraph

where every fourth trace of the input seismic data is converted to X-Y pairs whose X coordinate has an initial value of 400 and has been multiplied by UnitSc and sent to the X-Y plot program. For millisecond data time will now be in seconds with the first X value set to 0.400.

(2) Reverse mode

sis_xy -Nlog_data -Oseis_log -R -UnitSc 1.0

where log data consisting of depth-travel time pairs are converted into a seismic trace. The SmpInt of the output dataset will be determined from the first two entries on the first trace of the input log. The Unit Scalar of the output dataset is set to 1.0 to designate that the sample axis is in meters [or feet].

sis_xy -Ntime_data -Oseis_data -R -UnitSc 0.001

where x,y time data consisting of time,amplitude pairs are converted into a seismic trace. The SmpInt of the output dataset will be determined from the first two entries on the first trace of the input ASCII file. The Unit Scalar of the output dataset is set to 0.001 to designate that the sample axis is in milliseconds [UnitSc =1.0 would designate seconds].

sis_xy -Ntime_data -Oseis_data -R -UnitSc 0.001 -SI

where x,y time data consisting of time,amplitude pairs are converted into a seismic trace. The SmpInt of the output dataset will be determined from the first two entries on the first trace of the input ASCII file. The Unit Scalar of the output dataset is set to 0.001 to designate that the sample axis is in milliseconds [UnitSc =1.0 would designate seconds]. The -SI entry indicates that the sample axis in the x,y ASCII input is in seconds. This axis will be converted to milliseconds prior to USP trace construction.

BUGS

If the calculated input sample interval ever gets to be less than unity this program will set it to unity. When working with odd units care must be taken to ascertain that nothing bad has happened in the line header department.

If one choses to cat data into this routine when running on the INTEL architecture the data will still be in native form. The incorrect byte swap of the input actually crashes rtape with I/O error. Use a USP routine such as editt to pick the data up for piping and all will be fine.  

AUTHOR

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Index

NAME

SYNOPSIS

DESCRIPTION

Command line arguments

Discussion

EXAMPLES

BUGS

AUTHOR

COPYRIGHT