Animation

Overview

Animation of KML features is possible using through use of the <TimePrimitive>. Elements can be tagged with either <TimeStamp> which defines a single point time or <TimeSpan> which defines a range of times.

New KML: <begin> <end> <TimeSpan> <TimeStamp> <When>

Tutorial

Animation Using the Time Primitive

(1) Open UFOTime.kmz (linked to above) in Google Earth.
(2) The time slide should appear at the top of the view. It will look similar to this:



(3) Open the dialog box and reduce the animation speed to a low setting, and set the repeat mode to wrap. The time dialog box can be accessed by clicking on the small white clock to the left of the time slide. It will look similar to this:



(4) Adjust the time slider so the two end markers are a small distance apart. It will look similar to this:



(5) Play animation in Google Earth.
(6) Adjust the time slider till the two markers become one. It will look similar to this:



(7) Play animation in Google Earth. What happened?
(8) Adjust the time slider and time dialog box so there are two markers with the left one clamped at the beginning of the time window. They will look similar to this:




(9) Play animation in Google Earth.

Defining Time Spans

(10) Copy one of the UFO placemarks in to a text editor.
(11) All of the KML should be familiar except for elements related to Time. Identify these new KML elements and save as the file as ET.kml.
(12) Swap the <TimeStamp> and <when> elements for <TimeSpan>, <begin> and <end>. Define the begin time as 1944 and the end as 1970.
(13) Save as ET.kml and open in Google Earth.
(14) Adjust the time slider till the two markers become one (see 7).
(15) Make sure ET.kml and UFOTime.kmz are both "on" (i.e. checked in the sidebar listing) and play animation. What happens?
(16) The <TimeStamp> and <TimeSpan> elements are the two ways a temporal value can be added to KML features. How this will appear when animated (i.e. when the time slider is used) will depend on the settings used for the time slider. Read the KML documentation and experiment.

Format of DateTime in the Time Primitive

The dateTime values used within <TimeStamp> and <TimeSpan> are defined according to XML Schema time. The value can be expressed as yyyy-mm-ddThh:mm:sszzzzzz, where:

yyyy = four digit year
mm = two digit month
dd = two digit day
hh = two digit hour (24 hour clock)
mm = two digit minutes
ss = two digit seconds
T = separator between the date and the time,
z = time zone, using either Z (for UTC) or zzzzzz, which represents ±hh:mm in relation to UTC.

Exercises

(A) Create an animation of the following data (earthquakes.txt) using <TimeStamp>. Specify any settings required for the time slider in a description balloon associated with the document.

(B) Repeat exercise (A) using <TimeSpan> and no specific time slider settings.