Finding Map Information
The identify tool is the simplest way to retrieve attribute data about a feature on the map. Clicking the Identifier button will activate the Identifier plug-in, and set the mouse cursor into identifier mode.
- Select the layer to query in the legend. (The darker rectangle indicates the selected layer).
- If a shapefile layer is selected, the identifier window will be put into Shapefile mode.
- When the user clicks on shapes in the Shapefile, the table will show information from the attribute table on the shapes.
- The identify result tool has a limited radius of effect when clicking. The mouse button may be held down and dragged to form a box; features within this box will be shown in the identifier.
There are options to find features based upon searching the Attribute Table, either via Find or Query. To use these options, highlight the specific layer, right click and open the attribute table.
To search for text (string);
- Click on [Tools] then [Find]
- Type in the search string and click [OK]. The first feature with that search string will be selected.
- To go to the feature on the map Click on [View] then [Zoom to Selected Shapes]
This option is only useful if shapefiles do not have multiple features with this same text.
The Query tool allows users to build queries on fields to select features with similar attributes.
- Click on [Selection] then [Query]
- Build the query then [Apply]. For rules for queries, click on [Help] in the Query box.
- The features selected by the Query will be highlighted in the attribute table
- To highlight the features on the map click on [View] then [Zoom to Selected Shapes]
The field calculator allows the user to build an expression and use the results to populate an attribute column.
- To use, Click on [Tools] then [Field Calculator Tool]
- Build the Query - See Table Editor Functions for a list of functions which can be used
- Select the Field name the results will be saved to
- Click on OK