Map Animation with GE

This note describes the basic procedures for creating simple map animations for Google Earth.


Background: TimeStamp and TimeSpan Elements in KML

KML is the language for Google Earth.  Google Earth will automatically add a timeline control if the KML file contains the TimeStamp or TimeSpan elements.  The KML segment below specifies when the point will be displayed:

       <Placemark>
         <TimeSpan>
           <begin><![CDATA[1960-01-01]]></begin>
           <end><![CDATA[1963-01-01]]></end>
         </TimeSpan>
         <Point>
           <coordinates>
             -106.227034748875,34.9289275350805,0
           </coordinates>
         </Point>
       </Placemark>

If <end> is left unspecified, the point will be continuously displayed.  For polygon features, the code is longer but with essentially the same structure:

       <Placemark>
         <TimeSpan>
           <begin><![CDATA[1982-01-01]]></begin>
           <end><![CDATA[]]></end>
         </TimeSpan>
         <Polygon>
           <outerBoundaryIs>
           <LinearRing>
             <coordinates>
               -87.0659986269817,30.9181675150873,0
               -86.3887706596153,30.2080797324039,0
               -85.3184365526709,29.7266398862173,0
               -83.7974804501572,29.8395433928932,0
               -82.8074194133055,28.9559433234986,0
               -82.3150629151148,27.0218231589456,0
               -80.9552878101271,25.3912422371639,0
               -80.3718054146054,25.3029960994589,0
               -79.9688975669653,26.5191890681993,0
               -81.6385696503477,30.6712811685338,0
               -87.0659986269817,30.9181675150873,0
             </coordinates>
           </LinearRing>
           </outerBoundaryIs>
         </Polygon>
       </Placemark>

Data Requirement

There are three requirements.  First, the map features (Placemark) need to have a time attribute, either a time stamp or a time span.  Second, the data need to be in KML format.  Third, the coordinates must be in WGS84.

Preparing Animation Data in ArcMap

  1. Add or modified the attribute table so that it contains either a time stamp field (when) or time span fields (begin and end).  Note that the data type for these time attribute fields must be "Date".
  2. Specify appropriate map symbols for the layer.  Note that there is no one-to-one match of map symbols between ArcMap and Google Earth.
  3. Use the ArcMap extension "Export to KML" to export the layer.

Check out two simple examples at: K:\Courses\GEO600\Li\ge

Animating Image Data

It is also straightforward.  A good example is the global clouds animation.  Below is the essential structure for image animation:

<GroundOverlay>
    <name>2008-10-12, 04:00 UTC</name>
<TimeSpan>
    <begin>2008-10-12T04:00:00Z
    </begin><end>2008-10-12T16:00:00Z</end>
</TimeSpan>
<Icon>
    <href>http://www.barnabu.co.uk/files/clouds/20081012-0400.png</href>
    <viewBoundScale>0.75</viewBoundScale>
</Icon>
<LatLonBox>
    <north>90</north>
    <south>-90</south>
    <east>180</east>
    <west>-180</west>
    </LatLonBox>
</GroundOverlay>

The critical procedure is obtaining the right <LatLonBox>.  Google has provided this utility  to assist the process.

Further Reading / Browsing