#### Description:

This attribute controls how the values supplied for the SkyRef and SkyRefP attributes are used. These three attributes together allow a SkyFrame to represent offsets relative to some specified origin or pole within the coordinate system specified by the System attribute, rather than absolute axis values. SkyRefIs can take one of the case-insensitive values `"` Origin`"` , `"` Pole`"` or `"` Ignored`"` .

If SkyRefIs is set to `"` Origin`"` , then the coordinate system represented by the SkyFrame is modified to put the origin of longitude and latitude at the position specified by the SkyRef attribute.

If SkyRefIs is set to `"` Pole`"` , then the coordinate system represented by the SkyFrame is modified to put the north pole at the position specified by the SkyRef attribute.

If SkyRefIs is set to `"` Ignored`"` (the default), then any value set for the SkyRef attribute is ignored, and the SkyFrame represents the coordinate system specified by the System attribute directly without any rotation.

Type:

  String.

#### Applicability

##### SkyFrame

All SkyFrames have this attribute.
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