Geodetic observations require different post-processing to that of astronomy observations. The data is required to be submitted in a particular format. The Haystack Observatory Postprocessing System (HOPS) software is used for this purpose.

source ~/corr_test.setup

This contains the geodetic environment variables:

export HOPS_STATION_CODE=/nfs/apps/vlbi/lba_locations/hops_station_code.txt
export DEF_CONTROL=/nfs/apps/vlbi/lba_locations/fourfit_control.txt
export PATH=${PATH}:/nfs/apps/vlbi/hops/x86_64-3.8/bin
export HOPS_QUIET='SHH'
. ~/bin/hops.bash

The following variables also need to be defined:

export CORDATA=/Exps/exp_name/
export DATADIR=/Exps/exp_name/

where an example is:

export CORDATA=/data/corr/corrdat/p483a

From correlation the data need to be in the mark4 format:

difx2mark4

To run fourfit:

fourfit -txa 1234

This gives a set of plots to inspect.

To rerun fourfit:

fourfit -a 1234

The input data file for aedit is alist.out . This is created by the following command:

alist *

The experiment names (16383) need to be modified in this file to 1234.

Aedit also requires an .ovex file for input, not a .vex. This is generated from a perl script:

./nskd_ovex.pl p483a.01.skd >> 1234.ovex

Changes have been made to the perl script when reading in the source name as it was not pulling in the data correctly.

The .ovex file now contains data with 1-letter code station IDs (mk4_site_ID). These may be incorrect and need to be checked manually. This step will be incorporated into the nskd_ovex.pl code itself soon.

The complete list of Mark4 Station Codes

Station codes:

Put this file, 1234.ovex, in the 1234/ directory.

aedit allows the user to flag the baselines that have bad data.

To start aedit, reading in an input list:

aedit -f alist.out

Remove duplicate data based on SNR (or other parameters)

edit dup SNR

Print to screen a summary of the data:

sum 2

Choose parameters to use:

parameter 1 2 6 7

Write pcal to file:

pwrite pcal.txt

To sort, and only use data of certain quality:

gcodes 1-9
sort baseline
sort freq
edit input

To plot the data:

psplot

This is where data can be flagged as bad and removed from the data set.