Configuring the Virtual Globe

This file is out of date, the norwegian version is more updated

Java Web Start

The Virtual Globe is usually started as a Java Web Start application. JWS applications are started by activating a JNLP file. For a description of Java Web Start and the JNLP file see here.

The VirtualGlobeStarter script

The Virtual Globe server provides server script that automatically generates a JNLP file and even a html page that tests for the existence of Java at the clients computer, and gives some troubleshooting tips. The script is found at: http://www.virtual-globe.info/VirtualGlobeStarter.php. Examples of using this script is found as links all over the Virtual Globe pages (especially have a look in the viewpoints pages). A VirtualGlobeStarter URL is autoamtically generated and put on the clipboard for the current view position and dataset by selecting the menu item Tools/Copy link for current view.

VirtualGlobeStarter arguments:

viewpoint
Comma separated list of position and attitude parameters of initial viewpoint:
longitude
latitude
both decimal degrees
height
meters above sea level
compass direction
zero to the north, positive direction to the right
elevation angle
zero is horizontal, positive direction upwards
.
dataset
URL to a VGML file (see below).
name
name of this viewpoint in Tools/Viewpoints list.
libs
comma separated list of extra libraries. Currently only 'Xj3D' is recognized for 3D feature and VRML support.
request
type of request:
start
return the java Web Start JNLP file that starts the Virtual Globe. If there is no request argument this is the default.
page
return an information html page that tests for the existence of Java on the client computer, and initiates a download if necessary. It also describes the viewpoint and gives some hints for new users.
download
Download Java, only used internally.
Example: http://www.virtual-globe.info/VirtualGlobeStarter.php?name=Europe&request=page&dataset=http://www.virtual-globe.info/globe.vgml&viewpoint=4.787607927703958,27.52509436526137,3178271.6469249073,0.39637688320507086,-60.09160309417106

Example of starting with a local "dataset" file: http:///www.virtual-globe.info/VirtualGlobeStarter.php?dataset=file://localhost/C:/Documents%20and%20Settings/raa/Desktop/globe.vgml. Naturally, you have to provide your own VGML file first, as described in the next section. The VGML file can be stored on your own webserver or on your local computer. The only requirement is that it should be accessible through an URL from the Virtual Globe client.

The dataset configuration file

The datasets are configured in a Virtual Globe Markup Language (VGML) file. VGML uses an XML syntax and new users should first be familiar with the XML basics. Several guides are available on the Internet.

The configuration file describes the contents of the data viewed in the Virtual Globe application. Users can interact with the data by selecting data specific menues in the windows to the left of the 3D view.

For an example of a VGML file download and save: http://www.virtual-globe.info/globe.vgml. The file is commented and can be used for learning how to edit your own configuration files. Currently the following data items can be configured in the VGML file:

Elevation service
The elevation service is using a proprietary format that is currently only used by our own servers.
Map and image coverages
The map and image coverages can use Web Map Services (WMS) layers, and are very useful for those wanting to make custom configurations. The different layers can be enabled and disabled in the map layers data menues to the left of the 3D view.
3D features
The 3D features creates a 3D billboard object in the terrain. The billboard shows an image specified in the configuration file. An info URL can be attached to the object, and the contents are shown in your default web browser on clicking in the 3D object. Other feature types are planned.
Viewpoints
Viewpoint specifications similar to the viewpoint argument to the virtual globe starter script. Creatres selectable buttons in the data menues to the left of the 3D view.
Flight paths
References to flight path files. Record a flight by using the Tools/Flight path menu, and reference the generated file through an URL.

Simple example


<?xml version="1.0" encoding="ISO-8859-1"?>
  <vgml>
    <universe>
      <world base-url="http://www.virtual-globe.info">
	<viewpoint-set>
	  <viewpoint name="Europe">
            4.78760792770,27.525094365,3178271,0.39637688,-60.0
	  </viewpoint>
	  <viewpoint name="North America">
	    -98.17452747,18.241150,6758337,0.1405,-75.2	
	  </viewpoint>	
	</viewpoint-set>
        <globe-surface>
          <elevations href="srtm30plus.fcgi"/>
          <layered-pyramid-coverage href="WMSproxy.fcgi">
	    <wms-texture-set  
       	        host="onearth.jpl.nasa.gov"
	        command="wms.cgi">
	      <layer name="BMNG" min-pix-size="500" enabled="true"/>
	    </wms-texture-set>
          </layered-pyramid-coverage>
	  <feature-set>
	    <feature-list>
	      <feature lon="10.6988547" lat="59.9413160" 
	         info-url="http://www.sintef.no/">
	        <billboard board-height="600" stem-height="600"
		image="http://globe.sintef.no/SINTEF_hovedlogo_PMS295.gif"/> 
	      </feature>
	    </feature-list>
	  </feature-set>
        </globe-surface>
      </world>
    </universe>
  </vgml>

Description of VGML elements

Common framework

This is the common framework that surrounds the data content. The only parameter here is the base-url argument. The value is used as a basis for relative URLs in the rest of the file. 

<?xml version="1.0" encoding="ISO-8859-1"?>
  <vgml>
    <universe>
      <world base-url="http://www.virtual-globe.info">
        ...
      </world>
    </universe>
  </vgml>

Globe surface

The Globe Surface element defines the globe surface with the elevation service. It contains one elevations element, one coverage element (usually a layered-pyramid-coverage) and zero or more feature-sets. 

        <globe-surface>
          <elevations href="srtm30plus.fcgi"/>
          ....
        </globe-surface>

Coverage

A layered-pyramid-coverage consists of several map layers stored on the server or assembled from Web Map Services. The layers are composed on the server, transformed to the Virtual Globe internal coordinate system, converted to a graphics friendly format and cached on the server for fast access for later users. Users adding theyr own WMS servers should note that the WMS server must be accessible from the Globe server!

Arguments:

href
URL to the WMSproxy server, relative to the base-url. 

          <layered-pyramid-coverage href="WMSproxy.fcgi">
	    <wms-texture-set  
       	        host="onearth.jpl.nasa.gov"
	        command="wms.cgi">
	      <layer name="BMNG" min-pix-size="500" enabled="true"/>
	    </wms-texture-set>
          </layered-pyramid-coverage>

WMS maps


         <layered-pyramid-coverage href="WMSproxy.fcgi">
	    <wms-texture-set  
       	        host="ims.cr.usgs.gov"
	        command="servlet19/com.esri.wms.Esrimap/USGS_EDC_Ortho_133Urban"
		transparent="true">
	      <layer name="Mar_2002_0.3m_Color_Albuquerque" 
                 bbox="-106.885181144181, 34.863397889534, -106.367636294967, 35.2623245540334" 
                 max-pix-size="25" min-pix-size="1" enabled="true"/>
	      <layer name="Feb-Apr_2002_0.3m_ColorIR_Allentown-Bethlehem" 
                bbox="-75.2311507722967, 40.6235999909394, -75.1123224410419, 40.7994446095312" 
                max-pix-size="25" min-pix-size="1" enabled="true"/>
	    </wms-texture-set>
	    <wms-texture-set  
       	        host="onearth.jpl.nasa.gov"
	        command="wms.cgi">
	      <layer name="global_mosaic" min-pix-size="15" enabled="true"/>
	      <layer name="modis" min-pix-size="500" enabled="true"/>
	    </wms-texture-set>
          </layered-pyramid-coverage>
The wms-texture-set element defines a WMS server. It has the following arguments:
host
The name of the WMS host.
command
The command part of the WMS URL.
transparent
True for all except the totally earth covering base layer.

The layer element defines a layer in a WMS. It has the following arguments:

name
The WMS layer name
bbox
Bounding box of the data coverage, a comma separated list of min-longitude, min-latitude, max-longitude, max-latitude, all decimal degrees WGS84. The bounding box stops the Virtual Globe vasting resources trying to download WMS images where there are no data.
max-pix-size
Maximum pixel size of this layer, in meters on the ground. If ommitted the layer is visible all the way out.
min-pix-size
Minimum pixel size of this layer, in meters on the ground. If ommitted the layer is expected to have infinite resolution.
enabled
Enabled by default. Can be changed by the user in the data menu to the left of the 3D view.

3D Features

The globe currently has a very simple point feature functionality. Expect improvements in this functionality in the near future. 

	  <feature-set>
	    <feature-list>
	      <feature lon="10.6988547" lat="59.9413160" 
	         info-url="http://www.sintef.no/">
	        <billboard board-height="600" stem-height="600"
		image="http://globe.sintef.no/SINTEF_hovedlogo_PMS295.gif"/> 
	      </feature>
	    </feature-list>
	  </feature-set>
        </globe-surface>
A feature-set contains a feature-list. The feature-list contains features. A feature has the following arguments:
lat
lon
Latitude and longitude of point feature, decimal degrees, WGS84.
info-url
URL to info page for the feature. The info page is opened when the object is clicked. (optional)
Currently only one object type is availabe, a 3D billboard. It has the following arguments:
image
URL to image that is shown on the billboard.
board-height
stem-height
Height of the board and the stem, meters, terrain scale.
Contact: Rune.Aasgaard@norkart.no