geodetic new object

[stansmith907]

Schema rules for geodetic: "parameters for the shape of the earth."

Rules:

• [ ] optional

Definitions:

• datumIdentifier: {identifier} "the identification given to the reference system used for defining the coordinates of points."
• datumName: (string) "the identification given to the reference system used for defining the coordinates of points."
• ellipsoidIdentifier: (identifier) "the identifier and reference for the ellipsoid"
• ellipsoidName: {string} "identification given to established representations of the Earth's shape."
• semiMajorAxis: {real} "radius of the equatorial axis of the ellipsoid."
• axisUnits: {string} "units of the semi-major axis."
• denominatorOfFlatteningRatio: {real} "the denominator of the ratio of the difference between the equatorial and polar radii of the ellipsoid when the numerator is set to 1."

Rules:

• [x] datumIdentifier optional
• [ ] datumName optional
• [x] ellipsoidIdentifier optional
• [ ] ellipsoidName required
• [x] semiMajorAxis optional
• [x] axisUnits required optional
• [x] denominatorOfFlatteningRatio optional Note: FGDC does not handle ellipsoidIdentifier and thus requires all the remaining elements. ISO can handle either the identifier or the other elements when defining an ellipsoid.

mdJson:

{
   "spatialReferenceSystem": [
      {
         "referenceSystemType": "MD_ReferenceSystemTypeCode",
         "referenceSystemIdentifier": {},
         "referenceSystemParameterSet": {
            "projection": {},
            "geodetic": {
               "datumIdentifier": {},
               "datumName": "",
               "ellipsoidIdentifier": {},
               "ellipsoidName": "",
               "semiMajorAxis": 9.9,
               "axisUnits": "",
               "denominatorOfFlatteningRatio": 9.9
            },
            "verticalDatum": {}
         }
      }
   ]
}

FGDC mapping:

• Both horizontal datum name horizdn and ellipsoid name ellips seem to have the same name and placed into mdJson ellipsoidIdentifier.
• FGDC specifies axis units separately in the planar.planci.plandu element as shown below.

<metadata>
  <spref>
    <horizsys>
      <geodetic>
        <horizdn>World Geodetic System of 1984</horizdn>
        <ellips>World Geodetic System of 1984</ellips>
        <semiaxis>6378137.0</semiaxis>
        <denflat>298.257223563</denflat>
      </geodetic>
    </horizsys>
  </spref>
</metadata>

ISO 19115-2 mapping: The ellipsoid elements map to MD_EllipsoidParameters in ISO 19115-2 which is not yet implemented. The ISO MD_ReferenceSystem classes were not added to the ISO XSD so I have no means of verifying my example is correct. Further, adding these classes to an ISO record will cause validation against the XSD to fail.

    <gmd:referenceSystemInfo>
        <gmd:MD_CRS>
            <gmd:projection>
                <gmd:RS_Identifier>
                    <gmd:code>
                        <gco:CharacterString></gco:CharacterString>
                    </gmd:code>
                </gmd:RS_Identifier>
            </gmd:projection>
            <gmd:ellipsoid>
                <gmd:RS_Identifier>
                    <gmd:code>
                        <gco:CharacterString></gco:CharacterString>
                    </gmd:code>
                </gmd:RS_Identifier>
            </gmd:ellipsoid>
            <gmd:datum>
                <gmd:RS_Identifier>
                    <gmd:code>
                        <gco:CharacterString></gco:CharacterString>
                    </gmd:code>
                </gmd:RS_Identifier>
            </gmd:datum>
            <gmd:ellipsoidParameters>
                <gmd:MD_EllipsoidParameters>
                    <gmd:semiMajorAxis>
                        <gco:Real>9.9</gco:Real>
                    </gmd:semiMajorAxis>
                    <gmd:axisUnits>meters</gmd:axisUnits>
                    <gmd:denominatorOfFlatteningRatio>
                        <gco:Real>9.9</gco:Real>
                    </gmd:denominatorOfFlatteningRatio>
                </gmd:MD_EllipsoidParameters>
            </ellipsoidParameters>
        </gmd:MD_CRS>
    </gmd:referenceSystemInfo>

ISO 19115-3 mapping: Does not map to ISO 19115-1/3. This information was removed to ISO 19111 ( I do not have documentation at this time ).

[jlblcc]

So, should we require ellipsoidIdentifier or all: semiMajorAxis, axisUnits, denominatorOfFlatteningRatio?

Where does ellipsoidName map to? How does it differ from ellipsoidIdentifier?

[stansmith907]

So, should we require ellipsoidIdentifier or all: semiMajorAxis, axisUnits, denominatorOfFlatteningRatio?

I think it depends on if we want to write an FGDC or ISO record. FGDC requires ellipsoidName, semiMajorAxis, and demoninatorOfFlatteningRatio; ISO needs only an ellipsoidIdentifier, but will require semiMajorAxis, axisUnits, and demoninatorOfFlatteningRatio if ellipsoidIdentifier is not available.

This is part of the miss-match between FGDC and ISO that we try to accommodate. So, maybe require ellipsoidIdentifier OR (ellipsoidName, semiMajorAxis, axisUnits, and demoninatorOfFlatteningRatio).

Where does ellipsoidName map to? How does it differ from ellipsoidIdentifier?

In the internal object it maps to geodetic.ellipsoidName. Maps to Ellipsoid_Name in FGDC and is not used in ISO, it would be part of identifier if one was specified.

[stansmith907]

Dropped datumName and ellipsoidName.

[stansmith907]

So the rules become:

• [ ] datumIdentifier - optional
• [ ] ellipsoidIdentifier - optional
• [ ] (other elements) - if one, then ellipsoidIdentifier plus all other must be present