Grouped observations with covariance are formatted in the same way as grouped observations, but with a covariance or correlation matrix following each group. The covariance is separated from the data by a #end_set data definition command. This format is used for multistation GPS data. The format is:
inst_stn_definition trgt_stn_definition observation trgt_stn_definition observation trgt_stn_definition observation #end_set covariance_matrix_elements .... covariance_matrix_elements .... inst_stn_definition trgt_stn_definition observation trgt_stn_definition observation ....
If the observations are point observations then the instrument station line is omitted, that is:
trgt_stn_definition observation trgt_stn_definition observation trgt_stn_definition observation #end_set covariance_matrix_elements .... covariance_matrix_elements ....
The station definitions inst_stn_definition and trgt_stn_definition (instrument station definition and target station definition) define the station code (the station code from the coordinate file) and the height of the equipment above the station. The preceding #data command may specify that the height is to be omitted (with the no_heights option), in which case the height is treated as being zero.
Each observation definition (observation in the formats above) includes the value of the observation (e.g. the length for a distance measurement). It may also include the error of the observation, and additional information such as refraction coefficient codes, observation classifications, and so on. There may be more than one observation type on each line. For example a data block may hold readings from a total station which include horizontal angle, zenith distance, and slope distance. The contents of the observation section is defined in the preceding #data command.