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Hi, in this demonstration I will show you how to load a feature layer into TerraExplorer,
define the layer’s style, perform queries and edit data.
A feature layer is a visual representation of a geographic data set like political boundaries,
roads, or national airports, using geographic objects such as polygons, lines and points.
TerraExplorer supports various formats of feature layers that can be loaded to the project,
either from local files, such as Shapefile, Geodatabase MDB or MicroStation DGN, or from
server connections such as Skyline SFS or Oracle Spatial.
For the first example, I’m going to show you how to load a point shapefile layer.
When adding a layer to a project, TerraExplorer reads its coordinate system and reprojects
it on the fly to the project’s coordinate system. If the layer does not include coordinate
system information, it can be manually defined in the Coordinate System dialog box.
By selecting the “Entire Layer” load option, TerraExplorer pre-loads the entire layer’s data to my project.
I choose to create annotations and use City visibility settings.
In the layer settings I load all the attribute fields. Labels can be added to features using the annotation tab.
To do this, click the annotation tab, select text label symbols,
and set the text to the value of the Feature Name attribute field.
I then set the font size, style, altitude and pivot and click Import.
The layer is added to the project tree and its features are displayed on the terrain.
By default, the points are loaded with a pushpin icon. Let’s use icons based on an attribute value.
I select the layer to open the Layer Edit tab and then click Layer Properties.
On the Image File field let’s click Field by Attribute button, and use Feature_Type attribute
and User Defined classification.
We can specify the attribute value and its corresponding image file.
Let’s do the same for all values and click OK.
Notice how different features are displayed with a different icon based on their attribute value.
Styling Fields by Attribute can also be used to create a thematic map that represents spatial phenomena.
I load a polygonal shapefile that displays rooftops. This time I select streaming mode,
which means the data is dynamically added or removed from the view based on the viewer’s position.
This allows data of unlimited size to be displayed, since only the required information
is loaded into the scene.
From the layer properties, change the type to 3D buildings and use the Maximum Height attribute for the roof altitude.
Using the Field by Attribute, I can classify the buildings based on their height, by colorizing the faces.
See how the commercial and the residential areas are emphasized.
Some complex layers are already pre-styled.
For example, I select the Google Earth KMZ format to load a countries layer.
In this chapter I will show you how spatial and attribute based queries can be performed
in order to select and edit features.
Using the Select Feature, I can open the object’s properties and edit its attribute values.
Observe how the icon is changed accordingly.
Using the Control key, I can select several objects which then can be moved, deleted
or edited from the attribute table.
Features can also be selected based on their spatial relationship with other objects.
Using the Area query, I can select all the features within an area.
To select features within a distance of 100 meters from a road, I use Line query with buffer of 100 meter.
I can choose to include only features that entirely overlap with my drawn geometry,
or to include also those that partially intersect.
If a road feature already exists, I can select the features based on its geometry.
Queries can also be performed on attribute values.
To select all the Park features I open the attribute table,
select the attribute and the value and click Search.
From the Operation button I can select Show Exclusive to show only the results.
TerraExplorer Pro enables us to perform various spatial operations on the layer’s features.
Let’s review some of the operations. This layer contains 3 polygons.
I click Add Polygon to add a new feature to the layer, then draw a polygon and name it.
Selecting these two polygons I can use the Clip command to clip away from the yellow polygon
the area that overlaps with the green polygon.
The red and blue polygons are partially overlapping.
The Intersect command creates a new feature from the common areas of the two polygons.
I select the red polygon so that its attributes will be used for the intersection feature.
The Merge operation merges the red polygon and the yellow polygon into a new multi-part feature.
This time I’ll select the yellow polygon so that its attributes will be used for the merged feature.
By selecting the multi-part feature and using the explode all command,
the multi-part feature can be separated into its individual components
In this video we demonstrated how to define a feature layer’s style and how to perform
queries and spatial operations.