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Geomajas Google layer plug-in Table of Contents
List of Figures
List of Tables
List of Examples
- 2.1. Google layer dependency, using geomajas-dep
- 2.2. Google layer dependency, explicit version
- 2.3. Google layer dependency for GWT, using geomajas-dep
- 2.4. Google layer dependency for GWT, explicit version
- 2.5. Simple Google layer configuration
- 2.6. Google layer configuration
- 2.7. Configure to use satellite images and
- 2.8. Configure to use satellite images
- 2.9. Using custom URLs
- 2.10. Using a custom URL selection
- 2.11. Google layer max zoom level
- 2.12. Using the GoogleAddon
The Google layer allows you to use Google maps imagery as a raster
layer in Geomajas. There are three possible types of images which can be
displayed: the normal view displays street data, satellite view displays
satellite images and physical view displays a hybrid of street and elevation
information.
Note
Use of the Google Maps images is subject to Googles terms of use.
For details, check with Google, though the following URLs may help you
http://code.google.com/intl/nl/apis/maps/terms.html
and http://www.google.com/intl/en_ALL/help/terms_maps.html.
Table of Contents
Make sure your include the plug-in in your project. If you are using
Maven and the geomajas-dep dependency to manage versions, include
following dependency to your pom:
Example 2.1. Google layer dependency, using geomajas-dep
<dependency>
<groupId>org.geomajas.plugin</groupId>
<artifactId>geomajas-layer-google</artifactId>
</dependency>
If you are not using geomajas-dep to manage versions, then you need
to mention the version explicitly.
Example 2.2. Google layer dependency, explicit version
<dependency>
<groupId>org.geomajas.plugin</groupId>
<artifactId>geomajas-layer-google</artifactId>
<version>2.1.0</version
</dependency>
If you want to use these as part of an application using the GWT
face, then the dependencies change to:
Example 2.3. Google layer dependency for GWT, using geomajas-dep
<dependency>
<groupId>org.geomajas.plugin</groupId>
<artifactId>geomajas-layer-google-gwt</artifactId>
</dependency>
If you are not using geomajas-dep to manage versions, then you need
to mention the version explicitly.
Example 2.4. Google layer dependency for GWT, explicit version
<dependency>
<groupId>org.geomajas.plugin</groupId>
<artifactId>geomajas-layer-google-gwt</artifactId>
<version>2.1.0</version
</dependency>
Warning
When using the Google layer, it is your responsibility to comply
with the Google's terms of use. Some sources of information about
these terms include http://code.google.com/apis/maps/,
http://code.google.com/intl/nl/apis/maps/terms.html
and http://www.google.com/intl/en_ALL/help/terms_maps.html.
Some of the things you need to do include adding the Google API code
in your application (using a Google API key when not running on
localhost), and (from the GWT face), using the
GoogleAddon class to assure the copyright notices are
displayed on the map.
A base Google layer configuration looks as follows:
Example 2.5. Simple Google layer configuration
<bean name="google" class="org.geomajas.layer.google.GoogleLayer">
<property name="tilesEnabled" value="true" />
<property name="apiKey" value="" />
</bean>
Warning
If you are using 1.7.1 or earlier of the OpenStreetMap plug-in
then this configuration will not work. In that version we simplified
configuration by not forcing you to configure values you are not
allowed to change anyway. For the old version, the configuration would
look like this:
Example 2.6. Google layer configuration
<bean name="layerGoogle" class="org.geomajas.layer.google.GoogleLayer" >
<property name="layerInfo" ref="layerGoogleInfo" />
<property name="satellite" value="false" />
<property name="maxZoomLevel" value="21" />
</bean>
<bean name="layerGoogleInfo" class="org.geomajas.configuration.RasterLayerInfo">
<property name="crs" value="EPSG:900913"/>
<property name="maxExtent">
<bean class="org.geomajas.geometry.Bbox">
<!--
see http://cfis.savagexi.com/2006/05/03/google-maps-deconstructed
-20037508.342789, -20037508.342789 to 20037508.342789, 20037508.342789
-->
<property name="x" value="-20026376.393709917"/>
<property name="y" value="-20026376.393709917"/>
<property name="width" value="40052752.787419834"/>
<property name="height" value="40052752.787419834"/>
</bean>
</property>
<property name="tileWidth" value="256"/>
<property name="tileHeight" value="256"/>
</bean>
Note that these older versions do not allow all of the other
configurations.
You can add some properties to define the kind of images which are
produced. By default, the layer displays road information, but this can
be changed to either satellite or physical (roads+elevation) imagery.
The view style modes are exclusive, last set will be valid
Table 2.1. GoogleLayer image type configuration
GoogleLayer configuration satellite Set to true to use satellite view from Google. When this
and physical are false (the default), the normal view (showing
streets) will be used. Setting to true will reset physical to
false. physical Set to true to use physical view from Google. When this
and satellite are false, the normal view (showing streets) will
be used. Setting to true will reset satellite to false. maxZoomLevel Set to a number for which maps are available in the
region of interest, defaults to 19. The first zoom level has one
tile for the entire world, the second has four tiles
etc.
These are used in the following configuration.
Example 2.7. Configure to use satellite images and
increase max zoom level -->
<bean name="satellite" class="org.geomajas.layer.google.GoogleLayer">
<property name="tilesEnabled" value="true" />
<property name="satellite" value="true" />
<property name="maxZoomLevel" value="21" />
<property name="apiKey" value="" />
</bean>
Alternatively, you can also configure the display style using the
dataSourceName property in the layer info. This is shown in the example
below. However, it is preferred to use the properties on the layer
itself. This can be useful for the dojo face, which uses this property
to detect Google layers. Note that the suffix "@GoogleLayer" will
automatically be added. Possible values are "G_NORMAL_MAP",
"G_SATELLITE_MAP" and "G_PHYSICAL_MAP".
Example 2.8. Configure to use satellite images
and increase max zoom level -->
<bean name="satelliteDs" class="org.geomajas.layer.google.GoogleLayer">
<property name="tilesEnabled" value="true" />
<property name="layerInfo">
<bean class="org.geomajas.configuration.RasterLayerInfo">
<property name="dataSourceName" value="G_SATELLITE_MAP" />
<property name="crs" value="EPSG:900913" /> <!-- required property -->
<property name="tileHeight" value="640" />
<property name="tileWidth" value="640" />
</bean>
</property>
<property name="apiKey" value="" />
</bean>
You can also force the set of URLs to choose from, as in the
following example. Note that this may fail when setting the image type.
You can define the different options using ${level}, ${x} and ${y} for
the zoom level and tile coordinate. A simple configuration looks like
this:
Example 2.9. Using custom URLs
<bean name="googleSingle" class="org.geomajas.layer.google.GoogleLayer">
<property name="tilesEnabled" value="true" />
<property name="tileUrl"
value="http://maps.googleapis.com/maps/api/staticmap?center=${center}&zoom=${level}" />
<property name="apiKey" value="" />
</bean>
The Google layer allows configuration of the strategy to choose
the server to provide the tiles. Each of the image types can be served
from four servers. The default behaviour is to select the server using a
round robin strategy.
The strategy can also be configured. For example, the sample below
selects the class to use for the URL selection strategy (this needs to
implement UrlSelectionStrategy).
Example 2.10. Using a custom URL selection
strategy -->
<bean name="googleStrategy" class="org.geomajas.layer.google.GoogleLayer">
<property name="apiKey" value="" />
</bean>
By default the maximum zoom level is 19, but this can be modified
using the maxZoomLevel property if your data source supports a different
level.
Example 2.11. Google layer max zoom level
configuration -->
<bean name="googleMaxLevel" class="org.geomajas.layer.google.GoogleLayer">
<property name="tilesEnabled" value="true" />
<property name="maxZoomLevel" value="12" />
<property name="apiKey" value="" />
</bean>
To enable the display of copyright information on the map (to comply
with Google's terms of use), you should use the GoogleAddon. This can be
done using a line of code like:
Example 2.12. Using the GoogleAddon
map.registerMapAddon(
new GoogleAddon("google", map, GoogleAddon.MapType.SATELLITE, false));
This needs to be called on the MapWidget object. The first parameter
is the DOM id for the object, the second the map widget itself, the third
the type of imagery which needs to be used and the last indicates whether
the Google map should be made visible.
Note that you will need to add the Google API key in your html
source file to assure this can work (otherwise you will probably get an
exception from Google when not accessing the page on localhost.
