This tutorial introduces you to working with feature and mesh layers, using the Hurricane Michael Damage Management dataset to showcase some of TerraExplorer's abilities.
- Let's continue in the Hurricane Michael project from the previous tutorial (Open TerraExplorer > Open Project from SGS > Search for mexico_beach_emergency_response and click Open).
- Skyline created a mesh model not only of Mexico Beach, Florida, but also of nearby coastline states affected by Hurricane Michael. In the Project Tree, expand the New Bern folder, and double-click to fly to a mesh layer of New Bern, North Carolina.
By the time Hurricane Michael moved through North Carolina on October 11th, its wind speed had decreased sufficiently to categorize it as a tropical storm, rather than hurricane. This resulted in significantly less damage to the area compared to Mexico Beach, mostly downed trees, sporadic power outages, and some minor structural damage. To help New Bern in efficient recovery efforts, Skyline created a polygon feature layer classifying each building’s damage. Classification enables you to visually distinguish different areas of the mesh layer and perform spatial and attribute queries. (More about: Feature layers and Classifying mesh layers)
- Select the radio option of in the Project Tree to display this classification layer. The New Bern Buildings - Severity shapefile contains four levels of damage: Not Inspected, No Damage, Minor Damage, and Major Damage, with each category level displayed in a different color in the 3D Window. As you move the mouse over the colorized mesh you will see a tooltip with the building's damage level. This classification was instrumental in increasing the efficiency and focus of the disaster response. (More about: Classifying mesh layers)
- Most feature layers store attribute field values for each of their features. In the case of building layers, the attributes might contain information on the type of building, e.g., municipal or residential, or the year built. These values can be used to do any of the following: display information in the Information Query Tool results, control the appearance and behavior of layer features based on field attribute values, or perform actions on sets of layer features matching a specific set of attribute field values (e.g., display only features with a certain value).
Let's open the Attribute Table for the New Bern Buildings shapefile to see what attribute information is contained in it: Select the New Bern Buildings - Severity layer in the Project Tree, and then on the Feature Layer tab, select . (More about: Attribute queries). In the Attribute Table that opens, note all the different attributes. Let's say that we're interested in finding only the larger buildings. We can do so by filtering based on the Area attribute. In the Query builder section, enter an attribute (in our case "Shape_Area"), condition (>), and value (2000) and click Insert String. The search expression is then displayed in the Search String field. Click Search. Note how the number of search results decreased from 1000 to 45.
Now let's display in the 3D Window only the buildings that meet our query filter. In the Attribute Table dialog, click and then select Set Visibility by Attribute. Note how the number of buildings in the 3D Window has decreased significantly. Now let's remove the filter: Click > Select Clear Visibility by Attribute. All the buildings are once again displayed in the 3D Window.
- We can also query features in the layers to display their attribute information: On the Analysis tab > select Query. Then in the 3D Window, point to any building (see how it is highlighted in purple) and then click. Note the attribute information in the Query Results box.
- More advanced steps: Let's now create our own classification layer that classifies the type of debris (vegetative, construction, hazardous waste, household appliance, and soil/mud) for efficient debris clearance. In the Project Tree, expand the 3D City Models group, and select . Then on the 3D Mesh Layer tab, click Create Layer.
- In the Create Classification Layer dialog, enter a Layer Name and then some attributes, e.g., debris type, approximate quantity in kilo, urgency. Note that there can't be spaces in the attribute name. Set an appropriate Attribute Type for each of the attributes. And select which attribute's values should determine the colorization of the debris piles in the layer. In the example below, Color Classification is based on debris type, similar to what we saw in the example above. A feature layer is created in the Project Tree. (More about: Creating classification layers)
- Right-click your newly created layer in the Project Tree, and select Properties. Note that in the Fill Color field, a value appears in brackets, e.g., "[DebrisType]". This is the field that you selected above on which to base the colorization classification. Click Edit to open the Field by Attribute dialog in which you can associate a specific color with each attribute value, and then click OK.
- Now navigate to a few different piles of debris and for each pile do the following: On the Feature Layer tab > Add Polygon. Then in the 3D Window, draw a polygon around the debris pile by clicking in the desired locations for each of the polygon points, and then right-clicking to complete. In the property sheet that opens, set the values of the attributes. See how the color of the debris pile changes based on the debris type.
- See the resources below for more information on working with feature and mesh layers.
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