KML Height and Time

Height

GeoServer by default creates two dimensional overlays in Google Earth. However, GeoServer can output features with height information (also called "KML extrudes") if desired. This can have the effect of having features "float" above the ground, or create bar graph style structures in the shape of the features. The height of features can be linked to an attribute of the data.

Setting the height of features is determined by using a KML Freemarker template. Create a file called height.ftl, and save it in the same directory as the featuretype in your GeoServer data directory. For example, to create a height template for the states layer, the file should be saved in <data_dir>/workspaces/topp/states_shapefile/states/height.ftl.

To set the height based on an attribute, the syntax is:

${ATTRIBUTE.value}

Replace the word ATTRIBUTE with the name of the height attribute in your data set. For a complete tutorial on working with the height templates see Heights Templates.

Time

Google Earth also contains a "time slider", which can allow animations of data, and show changes over time. As with height, time can be linked to an attribute of the data, as long as the data set has a date/time attribute. Linking this date/time attribute to the time slider in Google Earth is accomplished by creating a Freemarker template. Create a file called time.ftl, and save it in the same directory that contains your data's info.xml.

To set the time based on an attribute the syntax is:

${DATETIME_ATTRIBUTE.value}

Replace the word DATETIME_ATTRIBUTE with the name of the date/time attribute. When creating KML, GeoServer will automatically link the data to the time element in Google Earth. If set successfully, the time slider will automatically appear.

For a full tutorial on using GeoServer with Google Earth's time slider see Time