Tagged: LAND-Geodesy - Page 2

The Canterbury region of New Zealand experienced a sequence of significant earthquakes during 2010 and 2011. These earthquakes occurred on 2010-09-04, 2011-02-22, 2011-06-13 and 2011-12-23. The coordinates in this layer account for all significant movements relating to these, so should be consistent with any observations made after the last earthquake to affect a given area (neglecting localised deformation such as that due to liquefaction).

Users may also be interested in the more comprehensive data in the companion layer Canterbury Earthquake Geodetic Marks (2010, 2011) - Comprehensive.

These coordinates are only provisional. Analysis is ongoing as further data is collected. Coordinates were calculated using SNAP v2.3.61. Stations were constrained using coordinates calculated by GNS Science. Some coordinates were calculated from data provided by Christchurch City Council. No precise levelling data has been used.

The estimated accuracy is 0.02m horizontally and 0.03m vertically.

The deformation model igns2011_working.grd calculated from a model (v4) provided by GNS Science on 28 April 2011 was used to remove secular deformation.

These coordinates are suitable for use in surveys and other geospatial activities in Canterbury and Christchurch.

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

The Canterbury region of New Zealand experienced a sequence of significant earthquakes during 2010 and 2011. These earthquakes occurred on 2010-09-04, 2011-02-22, 2011-06-13 and 2011-12-23. Precise-levelling surveys have been carried out throughout Canterbury and Christchurch to re-establish heights after these earthquakes.

Users may also be interested in the horizontal coordinates derived from GNSS data in the companion layers Canterbury Earthquake Geodetic Marks (2010, 2011) - Comprehensive and Canterbury Earthquake Geodetic Marks (2010, 2011) - Simple

Horizontal Accuracy (standard deviation) approx 1m.
Vertical Accuracy of Lyttelton Vertical Datum 1937 heights (standard deviation) 0.005m.

Heights generated from precise levelling data undertaken to a misclose standard (mm) of 5*sqrt(k) where k is the distance in kilometres. Precise levelling in the Christchurch area was undertaken after the 23 December 2011 earthquake. Other areas were levelled after the most recent earthquake to have affected heights in that area. Heights therefore represent the position of marks accounting for all four substantial Canterbury earthquakes.

These heights are only provisional. Analysis is ongoing as further data is collected.
Heights calculated using SNAP v2.3.64.
Heights were constrained using the pre-earthquake heights at geodetic codes AC9B, AFAQ, AG32 and B853. GNSS observations and modelling indicates that the height change of these marks was negligible.
Some heights were calculated from precise levelling data provided by Christchurch City Council.

These coordinates are suitable for use in surveys and other geospatial activities in Canterbury and Christchurch.

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

The LTN37-NZVD2016 grid enables the conversion of normal-orthometric heights from the Lyttelton 1937 local vertical datum to the New Zealand Vertical Datum 2016 (NZVD2016).

The conversion value is represented by the attribute “O”, in metres.

This conversion and NZVD2016 are formally defined in the LINZ standard LINZS25009.

LTN37-NZVD2016 is published on a two arc-minute grid (approximately 3.6 kilometres) extending over the benchmarks that nominally define the extent of the Lyttelton 1937 vertical datum (168.53° E to 174.2° E, 41.3° S to 45.1° S).

The height conversion grid models the difference between the Lyttelton 1937 vertical datum and NZVD2016 using the LINZ GPS-levelling marks. From the GPS-levelling marks the expected accuracy of LTN37-NZVD2016 is better than 2 centimetres (95% Confidence interval).

More information on converting heights between vertical datums can be found on the LINZ website.

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

Coordinates computed from surveys undertaken after the 14 February 2016 Canterbury earthquake. These should be consistent with any observations made after this earthquake (neglecting any localised deformation such as that due to liquefaction).

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

These coordinates are only provisional. Analysis is ongoing as further data is collected. Coordinates were calculated using SNAP v2.5.33. Stations were constrained using coordinates of distant PositioNZ continuous GNSS stations that were unaffected by the earthquake.

The standard deviations of coordinates are 0.01m horizontally and 0.02m vertically, relative to the PositioNZ network.

Coordinate changes due to the earthquake have been calculated by comparing pre and post-earthquake coordinates. Pre-earthquake coordinates were calculated relative to public and private continuous GNSS stations. These continuous GNSS stations had data processed for several days early in 2016 (before the earthquake). Other pre-earthquake geodetic data was then readjusted with the continuous GNSS data. Note that this means these coordinate changes may differ slightly from those that would be calculated by comparing the post-earthquake coordinates with those currently in the Geodetic Database.

These coordinates are suitable for use in surveys and other geospatial activities in Canterbury and Christchurch.

The OTP64-NZVD2016 grid enables the conversion of normal-orthometric heights from the One Tree Point 1964 local vertical datum to the New Zealand Vertical Datum 2016 (NZVD2016).

The conversion value is represented by the attribute “O”, in metres.

This conversion and NZVD2016 are formally defined in the LINZ standard LINZS25009.

OTP64-NZVD2016 is published on a two arc-minute grid (approximately 3.6 kilometres) extending over the benchmarks that nominally define the extent of the One Tree Point 1964 vertical datum (171.3° E to 174.4° E, 40.4° S to 42.7° S).

The height conversion grid models the difference between the One Tree Point 1964 vertical datum and NZVD2016 using the LINZ GPS-levelling marks. From the GPS-levelling marks the expected accuracy of OTP64-NZVD2016 is better than 1 centimetre (95% Confidence interval).

More information on converting heights between vertical datums can be found on the LINZ website.

The WGN53-NZVD2016 grid enables the conversion of normal-orthometric heights from the Wellington 1953 local vertical datum to the New Zealand Vertical Datum 2016 (NZVD2016).

The conversion value is represented by the attribute “O”, in metres.

This conversion and NZVD2016 are formally defined in the LINZ standard LINZS25009.

WGN53-NZVD2016 is published on a two arc-minute grid (approximately 3.6 kilometres) extending over the benchmarks that nominally define the extent of the Wellington 1953 vertical datum (174.4° E to 176.4° E, 39.1° S to 41.6° S).

The height conversion grid models the difference between the Wellington 1953 vertical datum and NZVD2016 using the LINZ GPS-levelling marks. From the GPS-levelling marks the expected accuracy of WGN53-NZVD2016 is better than 2 centimetres (95% Confidence interval).

More information on converting heights between vertical datums can be found on the LINZ website.

The NSN55-NZVD2016 grid enables the conversion of normal-orthometric heights from the Nelson 1955 local vertical datum to the New Zealand Vertical Datum 2016 (NZVD2016).

The conversion value is represented by the attribute “O”, in metres.

This conversion and NZVD2016 are formally defined in the LINZ standard LINZS25009.

NSN55-NZVD2016 is published on a two arc-minute grid (approximately 3.6 kilometres) extending over the benchmarks that nominally define the extent of the Nelson 1955 vertical datum (171.3° E to 174.4° E, 40.4° S to 42.7° S).

The height conversion grid models the difference between the Nelson 1955 vertical datum and NZVD2016 using the LINZ GPS-levelling marks. From the GPS-levelling marks the expected accuracy of NSN55-NZVD2016 is better than 2 centimetres (95% Confidence interval).

More information on converting heights between vertical datums can be found on the LINZ website.

Introduction
This dataset provides gravity observations, reductions and metadata for New Zealand’s national airborne gravity survey at flight elevation. A full description of each field in this dataset is available in the accompanying pdf NZ Airborne Gravity Flight Lines at Elevation (2013-2014) Description.

Description
New Zealand’s national airborne gravity dataset is comprised of more than 50,000 linear km of flight observations, covering the three main islands of New Zealand and up to 10km offshore.

Gravity observations can be used to compute gravity anomalies: differences between measured gravity and an ellipsoidal model of the Earth’s gravity field. Gravity anomalies correspond to un-modelled density variations within the Earth’s crust and upper mantle. They are used to investigate concealed geological structures and for quasigeoid modelling.

The national airborne gravity dataset was collected as a joint project between Land Information New Zealand (LINZ), GNS Science (GNS) and Victoria University of Wellington (VUW). The airborne survey was completed in a total of eight months, over two campaigns: August – October 2013, and February – June 2014.

Users may also be interested raster layers created for each of the free-Air and Bouguer Anomalies which have been downward continued to ground surface NZ Airborne Gravity Free-Air Anomalies at Ground Surface (2013-2014) and NZ Airborne Gravity Bouguer Anomalies at Ground Surface (2013-2014).

The AUK46-NZGD2000 grid enables the conversion of normal-orthometric heights from the Auckland 1946 local vertical datum directly to New Zealand Geodetic Datum 2000 (NZGD2000) ellipsoidal heights.

AUK46-NZGD2000 is published on a one arc-minute grid (approximately 1.8 kilometres) extending over the benchmarks that nominally define the extent of the Auckland 1946 vertical datum (174.0° E to 176.2° E, 36.1° S to 38.0° S).

The conversion value is represented by the attribute “delta”, in metres.

This grid is a combination of New Zealand Quasigeoid 2016 NZGeoid2016 and the AUK46-NZVD2016 height conversion grid. Where NZGeoid2016 is the reference surface for the New Zealand Vertical Datum 2016 (NZVD2016), while the AUK46-NZVD2016 grid models the difference between the Auckland 1946 vertical datum and NZVD2016 using the LINZ GPS-levelling marks.

More information on converting heights between vertical datums can be found on the LINZ website.