EPSG:1071

Vertical Offset by Grid Interpolation (NZLVD)

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Data source: OGP

Information source: IOGP

Revision date: 2019-03-22

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Definition: OGP XML

<div class="syntax"><pre><span class="cp">&lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;</span> <span class="nt">&lt;gml:OperationMethod</span> <span class="na">xmlns:epsg=</span><span class="s">&quot;urn:x-ogp:spec:schema-xsd:EPSG:1.0:dataset&quot;</span> <span class="na">xmlns:gml=</span><span class="s">&quot;http://www.opengis.net/gml/3.2&quot;</span> <span class="na">xmlns:xlink=</span><span class="s">&quot;http://www.w3.org/1999/xlink&quot;</span> <span class="na">gml:id=</span><span class="s">&quot;iogp-method-1071&quot;</span><span class="nt">&gt;</span> <span class="nt">&lt;gml:metaDataProperty&gt;</span> <span class="nt">&lt;epsg:CommonMetaData&gt;</span> <span class="nt">&lt;epsg:informationSource&gt;</span>IOGP<span class="nt">&lt;/epsg:informationSource&gt;</span> <span class="nt">&lt;epsg:revisionDate&gt;</span>2019-03-22<span class="nt">&lt;/epsg:revisionDate&gt;</span> <span class="nt">&lt;epsg:changes&gt;</span> <span class="nt">&lt;epsg:changeID</span> <span class="na">xlink:href=</span><span class="s">&quot;urn:ogc:def:change-request:EPSG::2016.031&quot;</span> <span class="nt">/&gt;</span> <span class="nt">&lt;epsg:changeID</span> <span class="na">xlink:href=</span><span class="s">&quot;urn:ogc:def:change-request:EPSG::2019.011&quot;</span> <span class="nt">/&gt;</span> <span class="nt">&lt;/epsg:changes&gt;</span> <span class="nt">&lt;epsg:show&gt;</span>true<span class="nt">&lt;/epsg:show&gt;</span> <span class="nt">&lt;epsg:isDeprecated&gt;</span>false<span class="nt">&lt;/epsg:isDeprecated&gt;</span> <span class="nt">&lt;/epsg:CommonMetaData&gt;</span> <span class="nt">&lt;/gml:metaDataProperty&gt;</span> <span class="nt">&lt;gml:metaDataProperty&gt;</span> <span class="nt">&lt;epsg:CoordinateOperationMethodMetaData&gt;</span> <span class="nt">&lt;epsg:isOperationReversible&gt;</span>true<span class="nt">&lt;/epsg:isOperationReversible&gt;</span> <span class="nt">&lt;epsg:signReversal</span> <span class="na">changeSign=</span><span class="s">&quot;true&quot;</span> <span class="na">xlink:href=</span><span class="s">&quot;urn:ogc:def:parameter:EPSG::8732&quot;</span> <span class="nt">/&gt;</span> <span class="nt">&lt;epsg:signReversal</span> <span class="na">changeSign=</span><span class="s">&quot;false&quot;</span> <span class="na">xlink:href=</span><span class="s">&quot;urn:ogc:def:parameter:EPSG::1048&quot;</span> <span class="nt">/&gt;</span> <span class="nt">&lt;epsg:example&gt;</span>For a point in the Dunedin 1958 height area at 44.42°S, 168.92°E (NZGD2000) with NZVD2016 height of 50.000 metres, to find its Dunedin 1958 height: First obtain the offsets at each of the surrounding grid nodes: NW corner 44.4000°S, 168.9000°E, offset = 0.3028m NE corner 44.4000°S, 168.9333°E, offset = 0.3029m SE corner 44.4333°S, 168.9333°E, offset = 0.3055m SW corner 44.4333°S, 168.9000°E, offset = 0.3051m Then using bi-linear interpolation for 44.42°S, 168.92°E, offset = 0.304m Then Dunedin 1958 height = 50.000 + 0.304 = 50.304m. For the reverse calculation to find the NZVD2016 height from a point with Dunedin 1958 height of 50.304m: First obtain the offsets at each of the surrounding grid nodes: NW corner 44.4000°S, 168.9000°E, offset = 0.3028m NE corner 44.4000°S, 168.9333°E, offset = 0.3029m SE corner 44.4333°S, 168.9333°E, offset = 0.3055m SW corner 44.4333°S, 168.9000°E, offset = 0.3051m Then using bi-linear interpolation for 44.42°S, 168.92°E, offset = 0.304m Then NZVD2016 height = 50.304 - 0.304 = 50.000m.<span class="nt">&lt;/epsg:example&gt;</span> <span class="nt">&lt;/epsg:CoordinateOperationMethodMetaData&gt;</span> <span class="nt">&lt;/gml:metaDataProperty&gt;</span> <span class="nt">&lt;gml:identifier</span> <span class="na">codeSpace=</span><span class="s">&quot;IOGP&quot;</span><span class="nt">&gt;</span>urn:ogc:def:method:EPSG::1071<span class="nt">&lt;/gml:identifier&gt;</span> <span class="nt">&lt;gml:name&gt;</span>Vertical Offset by Grid Interpolation (NZLVD)<span class="nt">&lt;/gml:name&gt;</span> <span class="nt">&lt;gml:formula&gt;</span>The relationship between NZVD16 height and thirteen local gravity-related coordinate reference systems (LVDs) for New Zealand is available through gridded data files of offsets (sometimes called height differences). The vertical offset at a point is first interpolated within the grid of values using bi-linear interpolation. For interpolation within the offset grids, horizontal positions in the NZGD2000 geographic 2D CRS are used. The interpolated value is then applied as an offset: • If the height in a LVD is required when a NZVD2016 height is given, add the interpolated offset to the NZVD2016 height (LVD height = NZVD2016 height + interpolated offset). • If the NZVD2016 height is required when a LVD height is given, subtract the interpolated offset from the LVD height (NZVD2016 height = LVD height - interpolated offset). Care! In the EPSG Dataset, offsets are additive (for the forward transformation). See EPSG Guidance Note 7-2, Implementation Notes - Offsets. The LINZ convention assumes that the offset is subtracted, and grid file names reflect that convention. The offset files therefore have names which conflict with the source and target CRSs of the EPSG transformation.<span class="nt">&lt;/gml:formula&gt;</span> <span class="nt">&lt;gml:generalOperationParameter</span> <span class="na">xlink:href=</span><span class="s">&quot;urn:ogc:def:parameter:EPSG::8732&quot;</span> <span class="nt">/&gt;</span> <span class="nt">&lt;gml:generalOperationParameter</span> <span class="na">xlink:href=</span><span class="s">&quot;urn:ogc:def:parameter:EPSG::1048&quot;</span> <span class="nt">/&gt;</span> <span class="nt">&lt;/gml:OperationMethod&gt;</span> </pre></div>
<?xml version="1.0" encoding="UTF-8"?>
 <gml:OperationMethod xmlns:epsg="urn:x-ogp:spec:schema-xsd:EPSG:1.0:dataset" xmlns:gml="http://www.opengis.net/gml/3.2" xmlns:xlink="http://www.w3.org/1999/xlink" gml:id="iogp-method-1071">
  <gml:metaDataProperty>
    <epsg:CommonMetaData>
      <epsg:informationSource>IOGP</epsg:informationSource>
      <epsg:revisionDate>2019-03-22</epsg:revisionDate>
      <epsg:changes>
        <epsg:changeID xlink:href="urn:ogc:def:change-request:EPSG::2016.031" />
        <epsg:changeID xlink:href="urn:ogc:def:change-request:EPSG::2019.011" />
      </epsg:changes>
      <epsg:show>true</epsg:show>
      <epsg:isDeprecated>false</epsg:isDeprecated>
    </epsg:CommonMetaData>
  </gml:metaDataProperty>
  <gml:metaDataProperty>
    <epsg:CoordinateOperationMethodMetaData>
      <epsg:isOperationReversible>true</epsg:isOperationReversible>
      <epsg:signReversal changeSign="true" xlink:href="urn:ogc:def:parameter:EPSG::8732" />
      <epsg:signReversal changeSign="false" xlink:href="urn:ogc:def:parameter:EPSG::1048" />
      <epsg:example>For a point in the Dunedin 1958 height area at 44.42°S, 168.92°E (NZGD2000) with NZVD2016 height of 50.000 metres, to find its Dunedin 1958 height:

First obtain the offsets at each of the surrounding grid nodes:
NW corner 44.4000°S, 168.9000°E, offset = 0.3028m
NE corner 44.4000°S, 168.9333°E, offset = 0.3029m
SE corner 44.4333°S, 168.9333°E, offset = 0.3055m
SW corner 44.4333°S, 168.9000°E, offset = 0.3051m

Then using bi-linear interpolation for 44.42°S, 168.92°E, offset = 0.304m

Then Dunedin 1958 height = 50.000 + 0.304 = 50.304m.

For the reverse calculation to find the NZVD2016 height from a point with Dunedin 1958 height of 50.304m:

First obtain the offsets at each of the surrounding grid nodes:
NW corner 44.4000°S, 168.9000°E, offset = 0.3028m
NE corner 44.4000°S, 168.9333°E, offset = 0.3029m
SE corner 44.4333°S, 168.9333°E, offset = 0.3055m
SW corner 44.4333°S, 168.9000°E, offset = 0.3051m

Then using bi-linear interpolation for 44.42°S, 168.92°E, offset = 0.304m

Then NZVD2016 height = 50.304 - 0.304 = 50.000m.</epsg:example>
    </epsg:CoordinateOperationMethodMetaData>
  </gml:metaDataProperty>
  <gml:identifier codeSpace="IOGP">urn:ogc:def:method:EPSG::1071</gml:identifier>
  <gml:name>Vertical Offset by Grid Interpolation (NZLVD)</gml:name>
  <gml:formula>The relationship between NZVD16 height and thirteen local gravity-related coordinate reference systems (LVDs) for New Zealand is available through gridded data files of offsets (sometimes called height differences). The vertical offset at a point is first interpolated within the grid of values using bi-linear interpolation. For interpolation within the offset grids, horizontal positions in the NZGD2000 geographic 2D CRS are used.

The interpolated value is then applied as an offset:
•	If the height in a LVD is required when a NZVD2016 height is given, add the interpolated offset to the NZVD2016 height (LVD height = NZVD2016 height + interpolated offset).
•	If the NZVD2016 height is required when a LVD height is given, subtract the interpolated offset from the LVD height (NZVD2016 height = LVD height - interpolated offset).


Care! In the EPSG Dataset, offsets are additive (for the forward transformation). See EPSG Guidance Note 7-2, Implementation Notes - Offsets. The LINZ convention assumes that the offset is subtracted, and grid file names reflect that convention. The offset files therefore have names which conflict with the source and target CRSs of the EPSG transformation.</gml:formula>
  <gml:generalOperationParameter xlink:href="urn:ogc:def:parameter:EPSG::8732" />
  <gml:generalOperationParameter xlink:href="urn:ogc:def:parameter:EPSG::1048" />
</gml:OperationMethod>