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# Intermagnet CD Data Viewer Help

# Data Viewing Options

It is not always clear what has been recorded in the 4th (total field) element of the archive format data files. Three different things could be stored here:

- A total field value computed from the main observatory vector data.
- A total field value recorded using an independant instrument (often a proton magnetometer).
- The difference between these two values.

The data viewer uses a number of rules to determine how total field data read from archive files is interpreted.

## The SCF database

The primary means for determining the type of total field data is the SCF database. This database is an Excel comma separated values (CSV) file, the same format used for the lists of countries and observatories. The database holds an entry for each individual year of data from each observatory. The entry may take one of four values:

- An 'S' in a year field indicates that F data was provided from an independant instrument.
- 'V' means F data was calculated from the main observatory instrument.
- 'D' means the value is a vector-scalar difference.
- Blank means no data.

The software uses the most recent version of the SCF files that it finds in the configuration directory ($HOME/.imag/). On Windows $HOME translates to your 'documents and settings' directory, so look for the files in somewhere like c:\documents and settings\your-username\.imag\ - on UNIX $HOME is your login directory.

Each time the software starts it checks for new versions of the file in the software distribution itself (i.e. inside the JAVA jar file). Any versions of the file found in the software distribution that are more recent than those in the configuration directory will be copied to the configuration directory and used immediately.

## Other rules

The SCF database does not cover all eventualities. For example, you may turn off use of the SCR database using the data viewing options dialog, or you may want to use data that is outside the range of the SCF database (ie data before or after the years listed in the database, or from non-INTERMAGNET observatories). To handle these situations a number of other rules are available. Whenever the software finds data that the SCF database cannot be applied to (for whatever reason) it will use these other rules:

Rule | Description
All F data is vector data | Any total field data outside the scope of the SCF database will be ignored (as it is assumed to be a redundant calculation from the XYZ or HDZ elements stored in the archive data format).
All F data is scalar data | Any total field data outside the scope of the SCF database will be used (as it is assumed to originate from an independant scalar instrument).
All F data is delta-F | Any total field data outside the scope of the SCF database is assumed to represent a difference value in the sense F(vector) - F(scalar).

Use the following rules:

This rule assumes that any total field data outside the scope of the SCF data:

- Is vector if it was recorded before a certain year
- Is scalar if it was recorded between this year and a later year
- Is difference data if it was recorded after the later year

The two year boundaries used in this rule can be set by the user in the data viewing options dialog.

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