An up-to-date set of geodetic data is built by downloading a monthly full data set, and then applying all daily incremental updates after the date of the monthly data set.

Note: It is recommended that the data set is maintained by rebuilding from new monthly updates as they become available. For technical reasons there are some changes that occur in Landonline and that are not reflected in the incremental updates. These may give rise to referential integrity errors between tables. For example it is possible for an incremental update to include a new mark name for which there is no corresponding mark. This will not occur in full updates.

Each table in the incremental data set contains only the records that have changed since the last update. These may be new records or records that have been edited. The primary key of the table must be used to determine which is the case - if a record already exists with the same primary key as the record in the new data then it is to be updated, otherwise it is inserted.

Generally geodetic data are not deleted from Landonline - they are just decommissioned (that is, their status is changed). The only data that may be deleted are data that have never been authorised. For example new coordinates may be calculated for points in Landonline, but never be authorised as the official coordinates of the mark. These coordinates may be deleted.

Any data that are deleted will be identifed in the aud1.csv file in the data set. Every other table includes a field called audit_id. The aud1.csv table lists the audit_ids that are to be deleted.