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PrePoint User Manual

• Introduction
• Description of Operation
• Operational Constraints, Premises, and Assumptions
• Command line options and flags
• Planned Enhancements
• Current Known Issues

Introduction

PrePoint is an application that pre-processes project scan data for input to the PTCS Pointing Models in MATLAB. PrePoint is intended for use with all-sky pointing observation projects, but is not limited to that type. It is project-centric, in that data are read and collated to the scan data collected during a project's observation time frame or subset thereof. Time-centric data, that is, collected via the sampler2log processes outside the project's observation time frame, are not used. PrePoint replaces glish scripts, producing data matching the format output by those scripts, as described at the bottom of PTCS Pointing Model input characterization. As of general GBT software Release 7.2, PrePoint produces the Astronomical Data portion of the required input. Additional modifications to this application are planned, to produce the other four required datasets.

Description of Operation

PrePoint is a command-line application, invoked with a statement and parameters from a command shell. Particulars of the arguments and flags with which the application may be invoked are described in detail below. In summary, one must specify the name of the project (to identify the data folder), and may include options for alternate data locations (-h), alternate output files (-o), type of pointing offsets (-a -lpc -d), the list of scans to process (-s), and whether to also display the results to screen (-v).

PrePoint processes the peak and focus scans of the project specified in the command, and writes a comma-separated ASCII file with a record for each scan-channel processed. At the top of the file is a header naming the fields contained in each record. If the PrePoint command is issued with such parameters that the intended output file already exists, the new data will be appended at the end of that file.

Operational Constraints, Premises, and Assumptions

Only peak and focus type scans from the specified project are processed; other scan types are ignored.

PrePoint processes two channels, assuming they represent X/L and Y/R polarization channels.

Command line options and flags

PrePoint is a command-line application. To run PrePoint, issue a command-line statement of the form:

prepoint <project> [-a] [-d] [-h <data home path>] [-lpc] [-o <output file name>] [-s <scan list>] [-v]

where

    project         : the name of the top-level data directory for the project
                      [ i.e., TPTCSPNT_060818 ]

    OPTIONS

    Options must be separated by spaces; multiple options may not be combined under a single
    option indicator (i.e., no '-ad').  If an option is specified which takes an additional 
    parameter ( -h, -o, -s ), the option symbol and parameter must be separated by a space also.

    -a            : includes the traditional pointing model in offset calculations

    -d            : for focus scans, includes dynamic corrections

    -h path       : specifies the directory in which the project 
                    data directory resides
                    [ if not specified, defaults to /home/gbtdata/ ]

    -lpc          : reports the previous local pointing correction values, instead of
                    including the traditional pointing model in offset calculations
                    - mutually exclusive with the '-a' option

    -o outputfile : filename to which data is written
                    [ if not specified, defaults to <project>.out in the
                      directory from which the prepoint application is run. ]

    -s scanlist   : specifies the list of scans to process
                    [ if not specified, or empty [], defaults to all scans in the project ]

                    individually specified scans:
                        bracketed, comma-delimited list of individual scan numbers.

                        -s [ 19, 23, 497 ]  -->  scans 19, 23, and 497

                    range of scans:
                        quoted RANGE command with desired starting scan number, and
                        end scan number value that is one larger than desired.

                        -s "range(1,5)"  -->  scans 1, 2, 3, and 4

                    complex list of ranges and individual scans:
                        combination of RANGE terms and bracketed terms, using '+'.

                        -s "range(1,5) + [8, 10, 13] + range(19,23)"  
                                  -->  [1, 2, 3, 4, 8, 10, 13, 19, 20, 21, 22]

    -v            : verbose mode; if specified, analysis data is printed
                    to standard output in addition to the data file

    -help         : prints this usage message; if used, should be the only option

Note: the vagaries of the scanlist option '-s' occur because PrePoint relies on the parsing capability of Python, rather than implementing what may be a more natual scanlist specification parser.

Planned Enhancements

Current Known Issues

-- RonGrider - 19 Mar 2007