Mapping between the header records and the data records

  In general, the order and number of the data records stored in the Data Values File may be different than the order and number of the header records stored in the Header Values File. This happens, for example, if the Header Values File has been reshuffled (e.g. sorted or transposed) while the Data Values File was left untouched. Whether the data and header records are in the same order is indicated by the value of the integer parameter same_record_number in the History File. The value of same_record_number is equal to 1 if the records are in the same order, and equal to 0 if they are not. If same_record_number is missing from the History File it is defaulted to 1. When the data and header records are in the same order (same_record_number=1), the association between header records and data records is given by the positions of the records in the respective binary files, and the Data Coordinate System coincides with the the Header Coordinate System. If data and header records are in different order the association between data records and header records is assured by the reserved header key data_record_number, that contains the data record number of the associated data record. The value of the data record number is defined as equal to the position of the data record in the Data Values File.