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use text string for WKT-CRS #89

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use text string for WKT-CRS #89

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eb4293d
use text string for wkt-crs
mo-marqh Dec 27, 2018
ad42621
return vertical datum example as WKT string
mo-marqh Dec 27, 2018
c9f4e70
escape characters for WKT
mo-marqh Dec 28, 2018
f664bfb
remove line returns
mo-marqh Dec 28, 2018
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33 changes: 8 additions & 25 deletions spec.md
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Expand Up @@ -408,37 +408,20 @@ Example of a vertical CRS, here representing height above the NAV88 datum:
```

#### 5.1.4 Providing inline definitions of CRSs
Sometimes there may be no well-known identifier for a geospatial CRS. Or the data provider may wish to make the CoverageJSON file more self-contained by avoiding external lookups. In this case a full inline definition of the CRS in JSON (instead of, or in addition to the `"id"`). This has not yet been fully defined in this specification, but we recommend following the OGC Well-Known Text (WKT) structure, for example:
Sometimes there may be no well-known identifier for a geospatial CRS. Or the data provider may wish to make the CoverageJSON file more self-contained by avoiding external lookups. In this case a full inline definition of the CRS in JSON (instead of, or in addition to the `"id"`) may be provided.

It is recommended that a Well-Known Text Coordinate Reference System String, conforming to the OGC WKT-CRS and ISO19162 joint specification is included as a string attribute.

The attribute name shall be `"WKTCRS"`.

The following example inlcudes escape characters for all of the double quote characters in the WKT-CRS, which are required.

```json
{
"type": "VerticalCRS",
"id": "http://www.opengis.net/def/crs/EPSG/0/5703",
"datum": {
"id": "http://www.opengis.net/def/datum/EPSG/0/5103",
"label": {
"en": "North American Vertical Datum 1988"
}
},
"cs": {
"id": "http://www.opengis.net/def/cs/EPSG/0/6499",
"csAxes": [{
"id": "http://www.opengis.net/def/axis/EPSG/0/114",
"name": {
"en": "Gravity-related height"
},
"direction": "up",
"unit": {
"symbol": "m"
}
}]
}
"WKTCRS": "VERTCRS[\"NAVD88 height\",VDATUM[\"North American Vertical Datum 1988\"],CS[vertical, 1],AXIS[\"gravity-related height (H)\", up],LENGTHUNIT[\"metre\", 1.0]]"
}
```

In future work, a mapping from OGC WKT2 to JSON may be defined, and may be adopted into the CoverageJSON specification.


### 5.2. Temporal Reference Systems

Time is referenced by a temporal reference system (temporal RS).
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