Exploring Maps

Finding a map to view

Note

It is advisable to use the public demo site http://demo.geonode.org/ for this section

To start searching existing maps, click the Explore Maps button on the front page.

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Here you will see a list of maps others have created, listed in the order in which they were created. Use the search box to find things you want.

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Next to the map titles are the names of the people who created them so you can contact them. GeoNode is about encouraging collaborations between people with common interests.

Click on the Alyssa Wright link in the Contact column: this will take you to Alyssa’s user profile. The profile displays all the maps and data that she’s responsible for.

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Let’s take a look at the Haiti Damage Assessment Map.

Map information page

Most links to maps in GeoNode go to that map’s information page, which displays metadata for that Map (Title, Abstract, contactable user) and provides other useful information and tools.

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To download all the layers in this map as a .zip file, click the Download all layers included in this map link. This will prompt you to log in to the site. If you do not have a user login on the site already, please follow the steps in the section Registering a new Account in GeoNode to register on the demo.geonode.org site.

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A page will be displayed listing the layers that cannot be download either due to security restrictions or because they are from another server.

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This page also links to other information pages about the data used in the map. Click the link to HaitiHealthFacilityMaster_20100125.

You should be directed to a new page with the metadata for this data set. Note that while the Map you were looking at was focused on Port-au-Prince, this page shows the entire data set of Haiti’s health facilities.

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From this page, you can download this data in various formats. For example, click the “JPEG” link in the upper left hand corner. This will give you a JPEG version of the data set via the open service WMS.

Look for the buttons in the Style section of this page. Click around to switch between different styles that users have made for this data.We will explore this sort of page in more detail later.

Go Back (in your browser) to the Map Information Page. Then click the link for View or edit this map. This will take you to the Map Composer, with a large map viewer and a side bar with a list of layers.

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Note on permissions

You need to have a registered user account to have permission to save a map. But you can still make changes to a map even when unregistered. Without permissions you will be able to add layers from GeoNode as well as add remote web services just for the session, but you will not be able to save your additions.

In previous chapter you created your own map, to which you have full permissions.

Currently this map is set to be viewable by anyone in the world.

Choice of basemaps

A number of preset basemap layers are available, including Google Satellite, the NASA Blue Marble satellite image, Open Street Map, and a No Background options. Other commercial and non commercial base maps can be added to a custom GeoNode installation.

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Ways to zoom

There are several ways you can zoom (change scales) in GeoNode:

  • Map navigation tools include the standard zoom bar and map drag
  • Roll your mouse wheel
  • Choose a scale from the scale bar readout
  • Zoom and pan simultaneously by defining a box on the map (shift-drag box) which upon release zooms you to the area you defined with the box
  • You can right-click on a layer name and select Zoom to Layer Extent to zoom to that layer

The shift-drag box approach may be the most powerful once you get the hang of it.

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Legend, Scale Bar

GeoNode generates legends automatically based on the SLD (Styled Layer Descriptor) symbolization. Legends for any layers being displayed are in the Legend tab next to the Data tab at the upper left.

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The scale bar changes with zoom level and the exact scale ratio is displayed.

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Layer on/off, Layer order, Transparency

You can turn layers on and off.

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Layers which are above others in the layer panel display on the map on top of those which are below. Display order can be changed by dragging and dropping layers up or down and the names of folders and layers can be changed.

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You can also change transparency of any layer by right clicking and going to Layer Properties > Display.

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Getting feature info

To see more information about a feature, click the Get Feature Info button at the far right of the toolbar.

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Then click on a feature on the map. The popup window will display the attributes of all features in the clicked-on location. GeoNode will return attributes for as many (vector) layers as you have turned on.

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Adding a layer from GeoNode

Click the Add Layers button, a green plus sign above the layer list. There is a dropdown of available servers from which you can add data and the option to add another WMS server (see below).

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Scroll down on the layer list and select the Haiti_Damage_Assessment_Points layer. You can click the + icon to see more information about the layer. Then add it to the map.

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Adding a layer from an external WMS Server

GeoNode supports the addition of a layer to a map via a web map service or WMS. Given a WMS URL to a remote server, GeoNode will request a list of all the Layers available on that remote server and display the list in GeoNode to select from and add to the Map.

Let’s look at how a remote WMS layer can be added.

Copy the World Health Organization URL.

In the Map Composer, click the Add Layers button and then click Add New Server.

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The following dialog will be displayed. You need to provide the URL to an external WMS. It is not strictly necessary to provide the query string arguments (?service=wms&request=GetCapabilities) portion of the URL as these will be appended to what you enter in the input text box. Paste the URL into the form and make sure there are no spaces at the end of the URL. Click Add Server.

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GeoNode will contact the remote server and get a list of its Layers via its GetCapabilities Document.

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When the GetCapabilities document has been fetched. The list of layers will be displayed and you can add them to the map as you would any other layer in GeoNode.

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Viewing a map in the embedded 3D Google Earth Viewer

GeoNode allows you to view a map in Google Earth with an embedded Google Earth Viewer. You will need to install the Google Earth plugin which is available from http://www.google.com/earth/explore/products/plugin.html. Once the plugin is installed, from the Map Composer, click the “Switch to Google Earth 3D Viewer” button in the toolbar to view the map with Google Earth.

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