| url | String | 'https://a.tile.openstreetmap.org' | optional
                
                
                
            
                The OpenStreetMap server url. | 
    
        
            
                | fileExtension | String | 'png' | optional
                
                
                
            
                The file extension for images on the server. | 
    
        
            
                | proxy | Object |  | optional
                
                
                
            
                A proxy to use for requests. This object is expected to have a getURL function which returns the proxied URL. | 
    
        
            
                | rectangle | Rectangle | Rectangle.MAX_VALUE | optional
                
                
                
            
                The rectangle of the layer. | 
    
        
            
                | minimumLevel | Number | 0 | optional
                
                
                
            
                The minimum level-of-detail supported by the imagery provider. | 
    
        
            
                | maximumLevel | Number |  | optional
                
                
                
            
                The maximum level-of-detail supported by the imagery provider, or undefined if there is no limit. | 
    
        
            
                | ellipsoid | Ellipsoid |  | optional
                
                
                
            
                The ellipsoid.  If not specified, the WGS84 ellipsoid is used. | 
    
        
            
                | credit | Credit
|
String | 'MapQuest, Open Street Map and contributors, CC-BY-SA' | optional
                
                
                
            
                A credit for the data source, which is displayed on the canvas. |