Where is a geodetic software package, used for professional analysis of VLBI data.
Running a VLBI analysis
To do an analysis with Where you only need to specify which analysis pipeline you want to run (i.e. VLBI), as well as the date and any pipeline specific options. For VLBI analysis you need to specify session_code. See the IVS observing program to find possible session codes. A basic Where command for VLBI is
where 2016 12 27 --vlbi --session_code=R1772
This command can be extended by setting any of the many configuration options
available for an analysis. Some of these will be described below. You can also
run where --help for a quick overview.
Configuration
Every Where analysis is based on a configuration which describes in detail how the analysis is performed, including
- which models are being used,
- which version of each model that is being applied, and
- which parameters are being estimated.
If you run Where like above - without specifying any particular settings - the default configuration is used.
By using the -E or --edit option open the configuration in your
standard editor and change it:
where 2016 12 27 --vlbi --session_code=R1772 -E
When you are happy with the configuration, save and close the configuration file the analysis will be executed.
Other useful options
If you want to delete a configuration (and any analysis done) you can use the
-D or --delete option:
where 2016 12 27 --vlbi --session_code=R1772 -D
To reset the configuration without deleting any of the previous analysis done,
use the -N or --new option:
where 2016 12 27 --vlbi --session_code=R1772 -N
The same option can be combined with the delete option, to immediately start a new configuration:
where 2016 12 27 --vlbi --session_code=R1772 -D -N
Where tries to skip stages that have previously been processed and where none of the dependencies for
that stage has changed. This behaviour can be overridden using the -F or --force option.
where 2016 12 27 --vlbi --session_code=R1772 --F
Then all stages will be reprocessed using the existing configuration.
Configuration profiles
The default configuration for VLBI is tuned for analyzing R1/R4 sessions. To
make it easy to analyze other kinds of sessions you can create profiles. This is done by appending __<profilename>
to the configuration parameter that you want to change. There are example profiles created for intensive sessions
and VGOS sessions. Example on use:
where 2020 1 9 -v --session_code=VO0009 --profile=vgos
Comparative analysis
If you want to do several analyses of the same session (for instance to compare different models etc), you need to mark the analysis with their own ids. For instance,
where 2016 12 27 --vlbi --session_code=R1772 --elevation:cut_off=0 --id=zero
where 2016 12 27 --vlbi --session_code=R1772 --elevation:cut_off=3 --id=three
This will run two Where analyses with different elevation cut-offs, stored with
the ids of zero and three.
Running many analyses
To analyze many sessions at once, use the where_runner tool. It has the same
form as the regular where command, except that it needs two dates: The start
date and end date of the analysis (both inclusive).
where_runner 2016 1 1 2016 12 31 --vlbi
The where_runner command does not need a --session_code option. It will run all
kinds of sessions that it finds. If you want to specify that only one or a few
types of sessions should be analyzed, you can still list them with the
--session_types option:
where_runner 2016 1 1 2016 12 31 --vlbi --session_types=R,CONT
In this example, Where will run all sessions that are of type R1/R4 and CONT and skip all other session types it finds. Session type in this context is a Where specific definition that refers to the first part of the session code that consist of letters (and not numbers). Meaning a session with code R1881 will have type R and a session with code AOV031 will have type AOV.