A very simple 
    
TerrainProvider that produces geometry by tessellating an ellipsoidal
surface.
| Name | Type | Description | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| options | Object | optional
                
                
                
            
                Object with the following properties: 
 | 
See:
Members
readonly availability : TileAvailability
    Gets an object that can be used to determine availability of terrain from this provider, such as
at points and in rectangles.  This function should not be called before
TerrainProvider#ready returns true.  This property may be undefined if availability
information is not available.
readonly credit : Credit
    Gets the credit to display when this terrain provider is active.  Typically this is used to credit
the source of the terrain.  This function should not be called before 
EllipsoidTerrainProvider#ready returns true.
readonly errorEvent : Event
    Gets an event that is raised when the terrain provider encounters an asynchronous error.  By subscribing
to the event, you will be notified of the error and can potentially recover from it.  Event listeners
are passed an instance of 
TileProviderError.
    Gets a value indicating whether or not the requested tiles include vertex normals.
This function should not be called before 
EllipsoidTerrainProvider#ready returns true.
    Gets a value indicating whether or not the provider includes a water mask.  The water mask
indicates which areas of the globe are water rather than land, so they can be rendered
as a reflective surface with animated waves.  This function should not be
called before 
EllipsoidTerrainProvider#ready returns true.
    Gets a value indicating whether or not the provider is ready for use.
    Gets a promise that resolves to true when the provider is ready for use.
readonly tilingScheme : GeographicTilingScheme
    Gets the tiling scheme used by this provider.  This function should
not be called before 
EllipsoidTerrainProvider#ready returns true.
Methods
    Gets the maximum geometric error allowed in a tile at a given level.
    
| Name | Type | Description | 
|---|---|---|
| level | Number | The tile level for which to get the maximum geometric error. | 
Returns:
    The maximum geometric error.
    
    Determines whether data for a tile is available to be loaded.
    
| Name | Type | Description | 
|---|---|---|
| x | Number | The X coordinate of the tile for which to request geometry. | 
| y | Number | The Y coordinate of the tile for which to request geometry. | 
| level | Number | The level of the tile for which to request geometry. | 
Returns:
    Undefined if not supported, otherwise true or false.
    
    Makes sure we load availability data for a tile
    
| Name | Type | Description | 
|---|---|---|
| x | Number | The X coordinate of the tile for which to request geometry. | 
| y | Number | The Y coordinate of the tile for which to request geometry. | 
| level | Number | The level of the tile for which to request geometry. | 
Returns:
    This provider does not support loading availability.
    
requestTileGeometry(x, y, level, request) → Promise.<TerrainData>|undefined
    Requests the geometry for a given tile.  This function should not be called before
    
TerrainProvider#ready returns true.  The result includes terrain
data and indicates that all child tiles are available.
| Name | Type | Description | 
|---|---|---|
| x | Number | The X coordinate of the tile for which to request geometry. | 
| y | Number | The Y coordinate of the tile for which to request geometry. | 
| level | Number | The level of the tile for which to request geometry. | 
| request | Request | optional The request object. Intended for internal use only. | 
Returns:
    A promise for the requested geometry.  If this method
         returns undefined instead of a promise, it is an indication that too many requests are already
         pending and the request will be retried later.
    
