DSET: Direction Set Header

This record specifies that a set of direction (DIR) observations follows. If a sigma-record identifier is given, it applies to all directions in the set.

The format of the DSET record is as follows:

Columns 002-005: DSET
Columns 007-009: Sigma record identifier (see the SIGM record)

A (horizontal) direction set must be in the following format:
DSET [optional sigma ID]
[Set of DIR observation records]

Each DIR record in a DSET must have the same from-station specified.

If a sigma-record is used for a DSET, the standard deviation, the from-centering, and to-centering values are used to modify or define the standard deviations of the direction measurements in the DSET group.