Following analysis and modelling of geodetic data, LINZ has made a bulk spatial update in Landonline to account for the movement of marks resulting from the Christchurch earthquakes in 2010 and 2011.
This update also accounts for four other significant earthquakes that have affected the South Island since 2000.
All marks which have moved more than 0.05 metres have been updated, including some 400,000 parcels and 1,700,000 survey marks and boundary points. The largest coordinate updates are in the vicinity of the Darfield fault rupture, approaching two metres.
The areas covered by the adjustment can be seen here: http://data.linz.govt.nz/layer/1685
To help you adjust your spatial datasets in the affected areas, we have documented three methods:
- ArcGIS’s Project Tool (using NTv2)
- ArcMap’s Spatial Adjustment Tool or
- GDAL ogr2ogr program (using NTv2)
|Download files for ArcGIS’s Project (Data Management) Tool|
The following process is for applying the adjustment using the ArcGIS Project tool under the Data Management toolbox. This is the preferred method for ESRI users and doesn’t have the limitations of the Spatial Adjustment tool described below. It can be applied to data with a spatial reference system (SRS) of either NZGD 2000 or NZTM 2000. It applies the adjustment to any data in the affected areas of the South Island.
A few notes before you start
This is a quick and robust process and can be used to adjust large datasets; however it involves a small workaround. The ArcGIS Project tool requires that data is shifted from one coordinate reference system to another, whereas here we are shifting data without changing the coordinate reference system. To get around this we have included two projection files, NZGD_2000_Deformation_Model_20130801_Patch.prj and NZTM_2000_Deformation_Model_20130801_Patch.prj which are identical except in name to the New Zealand Geodetic Datum 2000 and New Zealand Transverse Mercator 2000 projection respectively. This ‘tricks’ the ArcGIS Project tool into accepting that it’s changing coordinate systems when it’s not.
This adjustment applies only to data with a SRS of NZGD 2000 or NZTM 2000. If you want to apply the adjustment to data that is in another SRS you will first have to convert it to NZGD 2000 or NZTM 2000.
Install the files:
- Unzip arcgis_project_files.zip. It contains four files that need to be saved to specific locations on your computer. Note: They are similarly named, so be sure you copy the appropriate files to the specified locations.
- Copy the file nzgd2000_deformation_model_20130801_patch_cadastral.gsb to the folder:
C:\Program Files (x86)\ArcGIS\Desktop<version>\pedata\ntv2\newzealand
Where <version> is your ArcGIS version number – 10.1, 10.2 etc
Note: Copying files under the Program Files directory may require administrative permissions on your computer.
Copy the file NZGD_2000_Deformation_Model_20130801_Patch.gtf to the folder:
C:\Documents and Settings\<login>\Application Data\ESRI\Desktop<version>\ArcToolbox\CustomTransformations
For Windows 7:
Copy the two .prj files NZGD_2000_Deformation_Model_20130801_Patch.prj and
NZTM_2000_Deformation_Model_20130801_Patch.prj to the folder:
C:\Documents and Settings\<login>\Application Data\ESRI\Desktop<version>\ArcMap\Coordinate Systems
For Windows 7:
Run the Project tool to apply the adjustment:
Note: The adjustment should only be applied once for each dataset. Running the adjustment more than once will shift the data more than once.
- Open the ArcCatalog’s Project tool from the Data Management toolbox and select the input dataset or feature class and specify the output dataset or feature class.
Check the Input Coordinate System is populated. In this example it’s NZGD 2000:
- Click the icon to the right of the Output Coordinate System textbox to open the spatial reference properties dialog box.
Expand the Favourites folder.
If the input data has a SRS of NZGD 2000 choose NZGD_2000_Deformation_Model_20130801_Patch as the output coordinate system.
If the input data has a SRS of NZTM 2000 choose NZTM_2000_Deformation_Model_20130801_Patch as the output coordinate system.
Here our data is in NZGD2000:
- Under the Geographic Transformation input box the transformation NZGD_2000_Deformation_Model_20130801_Patch should appear.
If it doesn’t appear check that you have copied all the files into the correct locations.
Click OK to run the transformation.
- Once the adjustment has completed, clean up the SRS by changing it from the custom SRS of NZGD_2000_Deformation_Model_20130801_Patch or NZTM_2000_Deformation_Model_20130801_Patch to NZGD 2000 or NZTM 2000 respectively.
To do this, right click on the layer in ArcCatalog and choose Properties…
The ‘real’ SRS can be selected under the XY Coordinate System tab.
Click apply to change the SRS.
To check the adjustment has been successful, compare the layer in ArcMap with the original. You can download the deformation model contours from the LINZ Data Service to determine the expected size of the adjustment.
Reversing the Adjustment
One of the advantages of this method is the adjustment can be reversed if needed.
- In ArcCatalog, browse to the feature class that you want to reverse the adjustment on. Right click on the feature class and choose Properties…
Under the XY Coordinate System tab:
For a feature class with a SRS of NZGD 2000 change it to: NZGD_2000_Deformation_Model_20130801_Patch
for a feature class with a SRS of NZTM 2000 change it to:
Look under the Favourites folder to find the deformation model SRSs.
Click Apply and then OKto close the dialog box.
- Open the Project tool from the ArcToolbox within ArcCatalog. Choose the Input Dataset or Feature Class that you’ve changed the SRS for in the previous step.
Specify an Output Dataset or Feature Class to create.Set the Output Coordinate System to the original SRS before it was changed in step one above; being either NZGD 2000 or NZTM 2000.
In the Geographic Transformation input box NZGD_2000_Deformation_Model_20130801_Patch should appear.
Click OK to run the transformation.
The following process is for applying the adjustment using ArcMap’s Spatial Adjustment tool.
There are two adjustment link files (one each for NZGD 2000 and NZTM 2000) for each of the following areas:
- Fiordland, and
- a highly accurate geodetic adjustment corresponding to the new version of the NZGD 2000 deformation model (this is a National adjustment and therefore includes both Canterbury and Fiordland areas).
|Files for use with ArcMAP’s Spatial Adjustment Tool|
|Area||NZTM 2000||NZGD 2000|
|Fiordland||fiordland _clpt_nztm.zip||fiordland _clpt.zip|
(Whole South Island)
Important: DO NOT apply the geodetic adjustment together with either Canterbury or Fiordland adjustments. However, you can apply the Canterbury and Fiordland adjustments to the same spatial data.
A few notes before you start
The link files can be read in by ArcMap’s Spatial Adjustment tool and define the rubbersheeting adjustment to be applied.
The Spatial Adjustment tool cannot handle large amounts of data. We have tested it successfully on a layer containing 7000 polyline features (in ArcMap 10.2), however layers larger than this may cause ArcMap to crash. For large layers, use ArcGIS’s Project tool as described above.
Tip: This adjustment edits the layer directly, so before adjusting your layer it’s strongly recommended to first back it up. As well as being good practice, it also is useful as a before and after check once the adjustment has been applied.
The layer must either be in the NZGD 2000 or NZTM 2000 coordinate reference system.
- Add the layer to ArcMap.
- Start an edit session: From the top navigation, click Edit > Start Editing.
- Add the Spatial Adjustment toolbar: From the top navigation, click Customize > Toolbars > Spatial Adjustment
- To load in the links file click Spatial Adjustment > Links > Open Links File…
Browse to the appropriate links file for the area you want to adjust and the coordinate reference system that matches your data.
- For Canterbury use canterbury_ctlpt_nztm.txt for layers in NZTM 2000, and canterbury_ctlpt.txt for layers in NZGD 2000.
- For Fiordland use fiordland_ctlpt_nztm.txt for layers in NZTM 2000 and fiordland_ctlpt .txt for layers in NZGD 2000.
For the high accuracy geodetic adjustment use geodetic_ctlpt_nztm.txt for layers in NZTM2000 and geodetic_ctlpt .txt for layers in NZGD 2000.
Note:It will take a few minutes for ArcMap to load the link file.
- Once the link file has loaded click Spatial Adjustment > Set Adjust Data and select the layer you want to adjust from the list.
- Set the adjustment method to “Rubbersheet”: click Spatial Adjustment > Adjustment Methods > Rubbersheet
- To run the adjustment click Spatial Adjustment > Adjust
- When the adjustment has finished click Editor > Save edits.
The following process is for applying the adjustment using ogr2ogr.
There are four adjustment link files to choose from; three apply the cadastral adjustment as applied to Landonline divided into Fiordland, Canterbury and the whole of the South Island for your convenience. The fourth file applies a highly accurate geodetic adjustment for the whole of the South Island, intended for geodetic use only.
- Canterbury cadastral adjustment
- Fiordland cadastral adjustment
- South Island cadastral adjustment (one file that combines the Canterbury and Fiordland adjustments), and
- a highly accurate South Island geodetic adjustment corresponding to the new version of the NZGD 2000 deformation model.
Important: DO NOT apply either of the two South Island adjustments with any other adjustment to the same data. However, you can apply the Canterbury and Fiordland adjustments to the same data.
OGR is part of the GDAL toolkit. It can be used to apply the adjustment using a NTv2 grid shift defined in the .gsb files.
GDAL/OGR can be freely downloaded for Windows, MAC and LINUX from this GDAL binary download page.
- Before running the adjustment, copy the appropriate .gsb grid file (see table above), to the <GDAL/OGR install directory>/share/proj directory.
Note: If the directory naming is different on your install, find it by searching for “nzgd2kgrid0005.gsb”. This file will be in the correct directory.
There are three adjustment grid files to choose from:
- For Canterbury use canterbury_ogr2ogr.gsb
- For Fiordland use fiordland_ogr2ogr.gsb
- For the high accuracy geodetic adjustment use geodetic_ogr2ogr.gsb (applies to the new version of the NZGD2000 deformation model).
Note:Make sure the source data has NZGD2000 as its coordinate reference system. We do not provide a file to adjust data that is in NZTM2000 for OGR2OGR.
Run the command below
ogr2ogr --debug on -f "ESRI Shapefile" -s_srs "+proj=longlat +ellps=GRS80 +nadgrids= geodetic_ogr2ogr.gsb" -t_srs "+proj=longlat +ellps=GRS80 +towgs84=0,0,0,0,0,0,0" shifted_data.shp data_to_shift.shp
Tip:This example shows how to apply the shift to a shapefile. Ogr2ogr supports most spatial data formats. To see all valid formats and for a usage guide to ogr2ogr type “ogr2ogr” in your command line.