EPSG:1071

Vertical Offset by Grid Interpolation (NZLVD)

Attributes

Data source: OGP

Information source: IOGP

Revision date: 2016-12-10

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Definition: OGP XML

<?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>2016-12-10</epsg:revisionDate>
         <epsg:changes>
            <epsg:changeID xlink:href="urn:ogc:def:change-request:EPSG::2016.031" />
         </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="false" 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. 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).

For interpolation within the offset grids, horizontal positions in the NZGD2000 geographic 2D CRS are used.</gml:formula>
   <gml:generalOperationParameter xlink:href="urn:ogc:def:parameter:EPSG::8732" />
   <gml:generalOperationParameter xlink:href="urn:ogc:def:parameter:EPSG::1048" />
</gml:OperationMethod>
<?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>2016-12-10</epsg:revisionDate>
         <epsg:changes>
            <epsg:changeID xlink:href="urn:ogc:def:change-request:EPSG::2016.031" />
         </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="false" 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. 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).

For interpolation within the offset grids, horizontal positions in the NZGD2000 geographic 2D CRS are used.</gml:formula>
   <gml:generalOperationParameter xlink:href="urn:ogc:def:parameter:EPSG::8732" />
   <gml:generalOperationParameter xlink:href="urn:ogc:def:parameter:EPSG::1048" />
</gml:OperationMethod>