6.5. Handling imagery layers

Cesium supports adding additional imagery layer to the Earth map by using the OGC compliant Web Map Service (WMS). Starting from version 2.0.0, the 3D web client also supports Web Map Tile Service (WMTS). The 3D web client provides a simple widget panel which allows the user to easily add and remove any imagery layers. The widget panel (1) (marked in the following figure) can be expanded and collapsed by clicking on the Imagery Layer button on the widget panel.

../_images/3d_web_client_wms.png

Fig. 6.12 The input panel (1) for adding a new imagery layer and the BaseLayerPicker widget (2) where the added imagery layers will be listed together with the per default available imagery layers

The parameters required for defining such imagery layers are described as follows:

Type

WMS for Web Map Service or WMTS for Web Map Tile Service

URL (*)

The location of the dataset on the web

Name (*)

The name of the imagery layer to be displayed in the BaseLayerPicker panel (2)

Sub-layers (*)

An imagery layer may contain one or more sublayers, whose names must be separated by comma

Style

(Only for WMTS) The style identifier available in the imagery dataset

tileMatrixSetID

(Only for WMTS) The TileMatrixSet identifier listed in the imagery dataset

Icon URL

The URL of the icon used for representing this imagery layer in the BaseLayerPicker

Tooltip

A text to be displayed when the mouse pointer is hovering over the layer’s icon

Other parameters

Additional parameters can be specified as key=value pairs separated by the & character

Proxy URL

Location of the proxy server used for cross-domain issues, such as /proxy/

The Proxy URL parameter helps the 3D web client to get around the cross-domain issue when performing HTTP requests. Since most of the WMS/WMTS server do not support CORS, a proxy running behind the 3D web client is required. If you use the JavaScript-based HTTP server shipped with the 3D web client or if you are using the 3D web client hosted on the 3DCityDB server, you do not need to change the default value, since there already exists a built-in proxy running with the relative path /proxy/. Otherwise, this parameter value must be adjusted according to the path of the proxy in use.

Usage example:

In this example, a WMS imagery layer provided by the Vorarlberg State Government will be added to and displayed in the 3D web client. The following parameter values should be entered into the corresponding input fields:

Type

WMS

URL (*)

http://vogis.cnv.at/mapserver/mapserv

Name (*)

Vorarlberg Aerial

Sub-layers (*)

wi2015_20cm

Icon URL

http://cdn.flaggenplatz.de/media/catalog/product/all/4489b.gif

Tooltip

Vorarlberg Aerial Photography taken during the winter 2015

Other parameters

map=i_luftbilder_r_wms.map

Proxy URL

/proxy/
../_images/3d_web_client_wms_gui.png

Fig. 6.13 Example showing how to add a new WMS layer to the 3D web client

Note

For your convenience, this example is readily available for access here.

As shown in the figure above, once the parameter settings have been completed, the WMS layer can be loaded by clicking on the Add / Update Imagery Layer button (3). Its icon image together with its label name (4) will be listed on the BaseLayerPicker widget (2). You can use the Geocoder widget (5) to zoom the Earth map to the region of Vorarlberg state and check the added WMS layer. Clicking on the Remove imagery layer button (6) will remove the WMS layer and replace it with the default imagery layer that is the first item listed on the BaseLayerPicker widget (2).