Difference between revisions of "GeoExplorer"

Revision as of 17:07, 26 June 2012

The GeoExplorer Portlet is a web application that allows users to interactive navigate, organize, analyze, search and discovery internal or external GIS Layers. GeoExplorer Portlet operates on a GeoNetwork instance in order to discover layers residing on a distributed e-Infrastructure.

Overview

GeoExplorer Portlet startup screenshot

The GeoExplorer Portlet provides the following facilities:

• Internal layers exploration (preview, sorting, filtering, multi-selecion);
• Interactive layers visualization on a Geospatial Map (zoom & pan);
• Visual correlation analysis of several overlying layers;
• CQL visual filter of one or more layers;
• Tabular spatial data retrieval of one or more layers;
• Transect layers analysis;
• Default Base Layers visualization (TrueMarble, GEBCO, relief, and so on);
• External WMS Layers management;

The webapp is partitioned into two logical components: the GeoExplorer area and the GisViewer area.

GeoExplorer Component

Fig. 1 - GeoExplorer panels subdivision

The GeoExplorer component offers an analytic view of all layers discovered by GeoNetwork. It consists of two panels: a tabular paging view of the layers (fig. 1.1), and a layer details contextual panel (fig. 1.2). The table exposes a summary of layers metadata, like the layer title, name and url of the Geoserver that stores this layer.

It's possible to:

• interactively move around the pages;
• operate filtering and sorting to search for a given layer;
• select one or more layers to be shown in the GisViewer;
• obtain on demand details for a selected layer (layer image preview, name, title, full name and so on);

In order to add a layer, a user can click on the AddLayer button in the table. In order to add several selected layers (by means of checkboxes), a user can click on the "Add Selected Layers" button (located on the top of the table).

Note: the layers are loaded by a csw global query on the GeoNetwork server; this query can take some minutes, therefore a cache is used for offering a rapid layers exploration. This cache is updated each 30 minutes, but it's possible to operate an "hard refresh" (by means of the update button on the top) to force reload.

GisViewer Component

Example of a GisViewer screenshot

A graphical map-based representation is crucial for enabling users to analyze layers containing geo-spatial data and to retrieve hidden information. Many layer tools have been developed oriented to user-friendly interaction.

Initially the GisViewer is a collapsed panel located on the top. By adding one ore more layers from the GeoExplorer Panel, the Gisviewer Panel automatically expands to show opened layers. However it's possible at any time to expand or collapse the panel by means of the Expand/Collapse button . Also the panel can be horizontally resized by the horizontal line between GeoExplorer and GisViewer Panels.

The GisViewer panel consists of three sub-panels: Layers Panel, Map Panel and Data Panel.

Layers Panel

The Layers panel (fig. 2) is the container for all layers that users want to analyze in a session study. This panel uses the "overlay" concept to able users to create a personal view map environment. The layers are represented by a dynamic sortable list, where the ordering denotes how the layers are superimposed with each other how they are shown on the map. Again, the layers can be selectively hidden/shown to smart focus on a different layers subset.

Each layer has integrated toolbar which allow different operations. This toolbar can be separately open for each layer, in order to have more flexibility (fig. 3).

From the layer tools it's possible to perform:

• Setting of layer opacity;
• Selection of an alternative layer style, if exists (fig. 4);
• Making of a CQL filter to display on the map (fig. 5);
• Saving a layer snapshot into the workspace or exporting in tha local space (fig. 6);
• Get a transect function on the layer by specifying a line on the map (fig. 7)

Map Panel

The Map Panel show a GIS navigable map of all visible layers, exploiting the OpenLayers javascript library. It's possible to pan and zoom on the map benefiting users to find geographic information.

Furthermore, a pop-up panel is included on thr right side of the map for base layer selection. Typically a base layer is a map such as "True Marble" or "GEBCO", useful to have a reference point for all visible layers (fig. 8).

Data Panel

The Data Panel is used to get tabular spatial data related to one or more layer on a defined geographical area. By default this panel is collapsed and it's shown when a spatial query is made, but at any time the panel can be expanded or collapsed.

From the Map Panel users can operate a spatial query to get visible layers information around a point on the map or a rectangular area. Simply clicking or drawing a rectangle on the map the query will start, and the Data Panel shown will contains all avaiable data for this spatial selection (there will be a table for each visible layer). It's also possible to export a csv data file for external analysis.

Fig. 8 - Base layer selection

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  Fig. 2 - Layers Panel

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  Fig. 3 - Layer Tools

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  Fig. 4 - Layer styles selection

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  Fig. 5 - Example of CQL filter on depth mean

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  Fig. 6 - Layers Panel

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  Fig. 7 - Layer transect operation