Google Earth Hacks

Rob Ratcliffrob@futuretek.com

Outline

Display Streaming GIS-related data to GE in near real time using push

Generating KML code from Java Interacting with GE via it’s COM and

KML interface Embedding GE into a Java application Demo

Target Scenario

EventServer

GEWrapperEvent

Listener

GPS Position and TimeAsynchronous Messages

GPS Position and Time

KML Over COM

Tomcat

Hack Alert

Comparison of XML Bindings for the GE Schema

XMLBeans JAXB Custom library called “gekmllib”

by Keith Powers

Target KML<?xml version="1.0" encoding="UTF-8" standalone="yes"?><kml xmlns="http://earth.google.com/kml/2.1"> <Document> <Folder> <name>This is the Root Folder</name> <description>Root Folder</description> <Folder> <name>Point Folder</name> <description>This is the Folder of Points</description> <Placemark> <description>Here is a point</description> <Point id="point1"> <coordinates>-97.5,20.1,0</coordinates> </Point> </Placemark> </Folder> </Folder> </Document></kml>

XMLBeans Generation

scomp -d c:/temp/kml -src c:/tmp/kmlsrc -out kml121.jar kml21.xsd

XMLBeans Usage

KmlDocument kmlDoc = KmlDocument.Factory.newInstance();KmlType kml = kmlDoc.addNewKml();

DocumentDocument dd = DocumentDocument.Factory.newInstance();DocumentType doc = dd.addNewDocument();kml.setFeature(doc); // doesn’t produce the right type

PlacemarkDocument pmd = PlacemarkDocument.Factory.newInstance();PlacemarkType pm = pmd.addNewPlacemark();doc.setFeatureArray(new FeatureType[] { pm});... Gave upSystem.out.println(kmlDoc.toString());

Don’t know if XMLBeans can be used on this schema...didn’t get it to work as expected given the currently generated API. (I think the GE’s type hierarchy is confusing XMLBeans or there is some other trick to using the API. Email me if you know the solution.)

JAXB Generation

xjc -d ..\src -p com.company.earth.jaxb -xmlschema -verbose kml21.xml

See generated classes at:

http://www.austinjug.org/presentations/ge-schema.gifhttp://www.austinjug.org/presentations/ge-relationships.gif

JAXB UsageJAXBContext context = JAXBContext.newInstance("com.jug.earth.bindings");ObjectFactory factory = new ObjectFactory();KmlType kmlType = factory.createKmlType();JAXBElement<KmlType> kml = factory.createKml(kmlType);DocumentType doc = factory.createDocumentType();JAXBElement<DocumentType> d = factory.createDocument(doc);kmlType.setFeature(d);FolderType rootFolder = factory.createFolderType();rootFolder.setName(“Root Folder”);rootFolder.setDescription(“This is the Root Folder");doc.getFeature().add(factory.createFolder(rootFolder));

FolderType childFolder = factory.createFolderType();childFolder.setName(“Point Folder”);childFolder.setDescription(“This is the Folder of Points");rootFolder.getFeature().add(factory.createFolder(childFolder));PlacemarkType pm = factory.createPlacemarkType();pm.setDescription("Here is a point");childFolder.getFeature().add(factory.createPlacemark(pm));PointType pt = factory.createPointType();pt.setId("point1");pt.getCoordinates().add("-97.5,20.1,100.0");pm.setGeometry(factory.createPoint(pt));Marshaller marshaller = context.createMarshaller();marshaller.setProperty("jaxb.formatted.output",Boolean.TRUE);marshaller.marshal(kml,System.out);

GEKMLLIB UsageKml kml = new Kml();Document doc = new Document();kml.addDocument(doc);Folder rootFolder = new Folder();rootFolder.setName("Root Folder");rootFolder.setDescription(“This is the Root folder");doc.addFolder(rootFolder);Folder childFolder = new Folder();childFolder.setName("Folder of Points");childFolder.setDescription("This is the a folder contained by the root");rootFolder.addFolder(childFolder);

Placemark pm = new Placemark();pm.setDescription(“Here is a point”);childFolder.addPlacemark(pm);Point pt = new Point();pt.setId(“point1”);pt.setNumericalCoordinates(new double[] {-97.5, 20.1, 100.0});pm.addPoint(pt);System.out.println(kml.toKML());

Conclusions GEKMLLIB had the most intuitive and

convenient bindings with the tradeoff that it has to be manually updated when the schema changes

JAXB produced more intuitive bindings than XMLBeans for the GE schema with less convenient bindings than GEKMLLIB

Don’t know if XMLBeans can even be used for the GE schema (needs further study)

Updating a KML Document

Can only do this using a request to a web server

Refreshes from local files are not allowed due to recently imposed security restrictions by GE

KML updates via COM do not update existing KML objects (or I didn’t see the way to do it.)

Index File<?xml version="1.0" encoding="UTF-8"?><kml xmlns="http://earth.google.com/kml/2.1"><Document id="trails">

<name>Trail Data</name><refreshMode>onChange</refreshMode><viewRefreshMode>never</viewRefreshMode><Folder id="trajectories">

<name>Sensor Trajectories</name></Folder>

</Document></kml>

Sample Network Link File<?xml version="1.0" encoding="UTF-8"?><kml xmlns="http://earth.google.com/kml/2.1"><NetworkLink id="31571602">

<name>TrailTrajectory</name><Link id="27682895"><href>http://localhost/trajectory.kml</href><refreshMode>onExpire</refreshMode><viewRefreshMode>never</viewRefreshMode></Link>

</NetworkLink></kml>

Sample Update File<?xml version="1.0" encoding="UTF-8"?><kml xmlns="http://earth.google.com/kml/2.1"><NetworkLinkControl><Update><targetHref>http://localhost/index.kml</targetHref><Create>

<Folder id="trajectories" targetId="trajectories"><Folder id="trajectories_001">

<name>Trajectories 001</name><Folder id=“rob">

<name>Rob</name></Folder>

</Folder></Create></Update></NetworkLinkControl></kml>

Update 2<?xml version="1.0" encoding="UTF-8"?><kml xmlns="http://earth.google.com/kml/2.1"><NetworkLinkControl><Update><targetHref>http://localhost/tags/index.kml</targetHref><Create><Folder id="trajectories" targetId="trajectories"><Folder id="trajectories_002"><name>Trajectories 002</name><Folder id="p006"><name>p006</name><Placemark id="p006_2008-02-26 16:39:44.75"><name>2008-02-26 16:39:44.75</name><TimeSpan id="8293453"><begin>2008-02-26T16:39:44.75Z</begin></TimeSpan><LineString id="2955420"><tessellate>true</tessellate><altitudeMode>clampToGround</altitudeMode><coordinates>-122.31170056139348,37.66159863308147,110.0 -122.24735227989765,37.69740212067616,109.99999999906868</coordinates></LineString></Placemark></Folder></Folder></Folder></Create></Update></NetworkLinkControl></kml>

Communicating with GE via COM using JaWin

What does JaWin do for me? Using the Type Browser to generate type-

safe classes from DLLs Source code examples

JaWin Type Browser

See generated diagram of generated classes at:http://www.austinjug.org/presentations/jawin.gif

Embedding GE Into Java Application

Source code browsing of salient hacks and JaWin code

Demos

Starting GE with JaWinIApplicationGE ge = new IApplicationGE("GoogleEarth.ApplicationGE");System.out.print("Initializing Google Earth ");while (ge.IsInitialized() <= 0) {

Thread.currentThread().sleep(350);System.out.print(".");

}System.out.println("\nGoogle Earth Initialized.\n");

Getting the Window Handle of the Peer Component of a JPanel

private int getGUIHwnd() {int hwnd = 0;System.loadLibrary("jawt");sun.awt.windows.WToolkit tk = (sun.awt.windows.WToolkit) this.getToolkit();Window w = SwingUtilities.getWindowAncestor(this);Object peer = tk.targetToPeer(w);Class c = peer.getClass();this.f = this.getDeclaredField(c, "hwnd"); // recurse through hierarchy // looking for “hwnd” variablef.setAccessible(true); // override permissionsObject result = f.get(peer);hwnd = ((Long) result).intValue();return hwnd;

}

Hack Alert!

Reparenting the GE Windowvoid attachRenderHwnd() {

//hide GE main windowtry {

User32.ShowWindow(getMainHwnd(), 0); //hide GE main window} catch (COMException e) {

e.printStackTrace();} catch (IOException e) {

e.printStackTrace();}

resizeGERenderHwnd();

//attach GE render window to the GUItry {

FuncPtr setParent = new FuncPtr("USER32.DLL", "SetParent");setParent.invoke_I(getRenderHwnd(), this.getGUIHwnd(),

ReturnFlags.CHECK_FALSE);} catch (COMException e) {

e.printStackTrace();}

}

GE Embedded In Prototype Java Application

References Google Earth Schema -

http://code.google.com/apis/kml/documentation XMLBeans - http://xmlbeans.apache.org JAXB - https://jaxb.dev.java.net/ GEKMLLIB - http://code.google.com/p/gekmllib/ JaWin - http://jawinproject.sourceforge.net/ See GE COM message board and Sun’s Java bug parade for

other examples of embedding windows