FREEZE MANAGEMENT FOR SURVEY CONVERSION

While survey conversion is in progress in an area, certain Landonline processes are prohibited to avoid data conflict and corruption. This is known as the Survey Conversion freeze.

LINZ has contracted EDS to undertake the Survey Conversion project. This involves EDS extracting from Landonline data in a freeze area, converting the relevant survey data (including integrating it with this existing data) and merging it back into Landonline. It is critical that affected data in Landonline has not been changed between the time it was extracted for conversion and the time the new related data is uploaded. If changes have occurred, such as new parcels or marks appearing, it is very likely the uploaded data will conflict with the new survey data, and in some cases overwrite it. This can seriously comprise the integrity of the record and involve complex resolution.

Considerable investigation has been undertaken to limit the affected processes to only those that could cause data conflict. Other processes may be permitted, but may require some rework once the underlying parcels are converted and the data uploaded into Landonline.

To help minimise the impact of the freeze, LINZ provides information to surveyors and implements internal freeze management processes. LINZ and EDS provide plans for surveyors showing the areas and dates for conversion - this may help surveyors prioritise their work. Landonline also includes a Conversion Freeze Areas layer in the spatial window that shows the extent of the freeze at the current time.

FREEZE DURATION

The unit of work for Survey Conversion is a Parcel Block, typically consisting of 100 - 150 parcels. To ensure that each block fits with its neighbours, both mathematically and topologically, a block cannot be uploaded until all of its neighbours have also been captured, adjusted, and quality assured. Along with the actual conversion time, this block dependency determines the length of the freeze for a given locality. The average Parcel Block is frozen for approximately three weeks.

Blocks on the edges of freeze areas (each consisting of about 35 Parcel Blocks) may need to wait until the neighbouring blocks in the abutting freeze area are also ready. Occasionally the abutting freeze area may not be started for a number of weeks, as other freezes may be scheduled for conversion first. These inter-freeze dependencies may cause some blocks to be held up for several weeks longer than normal. EDS, in consultation with LINZ, have attempted to schedule the freezes so that they have the minimal overall impact.