Data - Page 3

This layer provides all authoritative arc survey observations and is targeted at cadastral surveyors.

Only observations that have been captured in Landonline are available. This includes vectors that were re-captured in the Survey Capture Areas from survey plans lodged prior to Landonline and all survey observations since.

Individual cadastral surveys will commonly re-measure or re-use cadastral lines. Often they will be the same, however as the accuracy capability has increased over time, differences between 'old' and 'new' observations are more likely. Thus all survey observations include the reference to the Survey Plan.

This layer provides the extents of the data incorporated into an adjustment which has been completed as a Wide Area Cadastral Adjustment (WACA). These adjustments are undertaken in areas where there is already substantial survey-accurate data, but there are some inconsistencies in the data resulting from small changes to geodetic control coordinates and/or the progressive submission of additional Cadastral Survey Datasets (CSDs). The improvement of coordinates is controlled by a mathematical adjustment process using a Least Squares methodology. The adjustment/integration process results in increased mapping accuracy of surrounding spatial objects (e.g. parcels), the effect of which is some new observations or parcels appear to move. The extent of the change largely depends upon the accuracy of the underlying data. In general, movements will be no more than 10cm, as the WACAs target areas where coordinates already have fairly high spatial accuracy.

For further information about this dataset, see the Canterbury earthquake information.

Coordinates computed by adding the effects of deep-seated movement to survey points that had authoritative survey-accurate digital cadastre (SDC) coordinates immediately prior to 4 September 2010 (the first Canterbury earthquake). Marks that did not have SDC status at that time are not included in the dataset. Deep-seated movements were evaluated using the NZGD2000 deformation model.

• The 'nod_id' column is the Landonline node id. This is the unique identifier for the mark.
• The 'current_name' column is the Landonline mark name. Many boundary marks do not have a name recorded in this dataset, because this information has not been digitally captured.
• The 'east_mtpleatm2000' and 'north_mtpleatm2000' columns are the east and north coordinates (metres) in terms of the Mt Pleasant 2000 transverse mercator projection. Rounded to the nearest centimetre.
• The 'coord_order' column is the Landonline coordinate order immediately prior to 4 September 2010.

The estimated absolute uncertainty of these coordinates is 0.09m at the 95% confidence level.

These coordinates are intended for the use of Licensed Cadastral Surveyors when locating boundaries in Christchurch, in accordance with the Rules for Cadastral Survey 2010 and associated guidance, particularly guidance relating to the earthquakes.

This layer details the movement of survey marks due to the Canterbury Earthquake Sequence (CES). The movements include the impact of 5 major earthquakes on 4 September 2010, 22 February 2011, 13 June 2011, 23 December 2011 and 14 February 2016.

Note that these movements apply only at the survey mark. Nearby land may have moved differently, especially in areas impacted by substantial shallow ground movement.

For further earthquake information, see the Canterbury earthquake information on the LINZ website.

Scope

Movements do not include the regular tectonic movement (not related to earthquakes) of approximately 5cm per year.

As well as Christchurch, the data covers Lyttelton, Spencerville, Kaiapoi, Pines Beach, Woodend, Pegasus and Waikuku Beach.

Mark Movement Calculations

Observed mark movements have been calculated from geodetic and cadastral survey data collected at the same physical survey mark before and after the earthquakes. Various filters have been applied to ensure as far as practicable that the movements reflect real-world earthquake-related movements of marks. For example, only non-boundary marks that have been directly measured (rather than adopted) are included.

Modelled mark movements have been calculated using models of the tectonic-scale movements resulting from each earthquake, supplied by GNS Science, supplemented with more detailed modelling carried out by LINZ. These models typically represent deep-seated movement only. They do not include shallow movement, such as that resulting from liquefaction.

Therefore the difference between the post-earthquake observed and post-earthquake modelled position generally represents shallow ground movement. The difference between the post-earthquake modelled and pre-earthquake observed position generally represents deep-seated movement. The difference between the post-earthquake observed position and pre-earthquake observed position represents total movement due to the earthquakes.

Accuracy

The uncertainty of the coordinate changes is 0.1m at a 95% confidence interval.

Layer Attributes

• nod_id_post_eq: Landonline node id for the latest post-earthquake node (mark)
• code_post_eq: Geodetic code for the latest post-earthquake node
• name_post_eq: Mark name for the latest post-earthquake node
• nod_id_pre_eq: Landonline node id for the pre-earthquake node (mark)
• code_pre_eq: Geodetic code for the pre-earthquake node
• name_pre_eq: Mark name for the pre-earthquake node
• de_mod_obs: East change from modelled post-earthquake to observed post-earthquake position
• dn_mod_obs: North change from modelled post-earthquake to observed post-earthquake position
• hz_mod_obs: Horizontal change from modelled post-earthquake to observed post-earthquake position
• bg_mod_obs: Bearing from modelled post-earthquake to observed post-earthquake position
• de_pre_mod: East change from observed pre-earthquake to modelled post-earthquake position
• dn_pre_mod: North change from observed pre-earthquake to modelled post-earthquake position
• hz_pre_mod: Horizontal change from observed pre-earthquake to modelled post-earthquake position
• bg_pre_mod: Bearing from observed pre-earthquake to modelled post-earthquake position
• de_pre_obs: East change from observed pre-earthquake to observed post-earthquake position
• dn_pre_obs: North change from observed pre-earthquake to observed post-earthquake position
• hz_pre_obs: Horizontal change from observed pre-earthquake to observed post-earthquake position
• bg_pre_obs: Bearing from observed pre-earthquake to observed post-earthquake position

For further information about this dataset, see the Canterbury earthquake information.

Coordinates computed by adding the effects of deep-seated movement to survey points that had authoritative survey-accurate digital cadastre (SDC) coordinates immediately prior to 4 September 2010 (the first Canterbury earthquake). Marks that did not have SDC status at that time are not included in the dataset. Deep-seated movements were evaluated using the NZGD2000 deformation model.

• The 'nod_id' column is the Landonline node id. This is the unique identifier for the mark.
• The 'current_name' column is the Landonline mark name.
• The 'east_mtpleatm2000' and 'north_mtpleatm2000' columns are the east and north coordinates (metres) in terms of the Mt Pleasant 2000 transverse mercator projection. Rounded to the nearest centimetre.
• The 'coord_order' column is the Landonline coordinate order immediately prior to 4 September 2010.

The estimated absolute uncertainty of these coordinates is 0.09m at the 95% confidence level.

These coordinates are intended for the use of Licensed Cadastral Surveyors when locating boundaries in Christchurch, in accordance with the Rules for Cadastral Survey 2010 and associated guidance, particularly guidance relating to the earthquakes.