About Where

Where is a Python Software package used for analyzing geodetic data. Currently, the software only supports VLBI data, but work is underway also for other techniques. The Where software is made available to the geodetic community as an open source, MIT-licensed project.

Getting Where

The latest release of Where is version 0.21.2. It can be downloaded through GitHub. See Installing Where for details on how to install the software.

License

Where is developed at the Norwegian Mapping Authority and made available under an MIT license. The MIT license is permissive allowing you to use, modify and distribute the software, as long as copyright and license notices are preserved.

Acknowledgement and Citing

If you are using Where for work or research, in presentations or as part of a code or analysis project, we ask that you acknowledge or cite Where as appropriate.

Software Overview

For information on how to get started using Where, see the Quickstart tutorial.

Where is built as a modular software so that it is easy to customize how the analysis done, change which models are used, and even write new models. The following describes some key concepts of the Where software.

Pipeline

A pipeline is a description of a particular analysis. Currently, Where only supports the VLBI pipeline which can analyze VLBI data. Through configuration profiles the VLBI pipeline can be set up to analyze different kinds of VLBI sessions, including R1/R4- and intensive sessions.

Analysis

An analysis is a pipeline applied to specific data. Typically, an analysis is the result of running Where on one VLBI session. The product of an analysis is a dataset containing all the input and output of the analysis. In addition, further products like sinex files, estimation parameters, maps etc may be written at the end of an analysis.

Configuration

Each Where pipeline has a configuration which defines the details of how the analysis is done. Examples of configuration settings for VLBI include

  • which observation format to use (NGS or vgosDB)
  • how to clean the data before analysis
  • which site displacement models to apply
  • which reference frame to use for a priori station coordinates
  • which parameters to estimate

For each analysis, the pipeline configuration is copied and can be tailored to the specific session that is being analyzed, for instance by specifying clock breaks, or that observations for a given radio source should be discarded.

Configuration Profile

In order to simplify configuring Where for different kinds of VLBI sessions, several configuration profiles are defined. The default configuration for VLBI is tuned for R1/R4 24-hour sessions. The same configuration does not work well for intensive sessions, for example, due to there being much fewer observations so that only a few variables should be estimated. This is supported by using the intensives configuration profile.

Dataset

Both input data and results from the modeling are stored in a Where dataset. A dataset essentially consists of corresponding time series for all relevant variables in an analysis.

A dataset can be explored interactively in the companion There software. In addition, Where can transform a dataset to other useful products such as SINEX files, estimated parameters or maps quantifying the result of an analysis.