Using Spatial Data with SAS/GIS Software

Defining Layers in Imported Data

In addition to identifying the default composites, a preliminary step of the import is to identify all of the layers that will be created by the import. Each layer represents a set of features on the map and how those features will be displayed. With the exception of the TIGER and DYNAMAP import types, which have a standard set of predefined layer definitions, the layer definitions are based on attributes that are found in the input data. Then, during the import, the layers are actually created. However, you can review the default layer definitions before the import takes place, and you can modify them if you choose.

Before selecting the [Import] button, you have to fill out the INPUT and OUTPUT sections on the GIS Spatial Data Importing window. Then you can select the [Modify Layers] button, which opens the Import window as shown in Import Window -- Modifying Layers.

Import Window -- Modifying Layers

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When the window is first displayed, the first layer in the Layer Names list is selected and its definition is displayed in the window. This list contains all of the layers that will be created for this import. To review a layer, click on its name in the Layer Names list box. All of the information in the window will be updated for the selected layer. You can now modify any of the fields. Unlike the Import window for modifying composites, all the fields in the window, except the Layer Statement field, are immediately editable, and none are hidden. Import Window Fields for Modifying Layers describes each of the fields and their uses.

Import Window Fields for Modifying Layers
Text Fields/Buttons Type Use

Layer Names List Selectable list of layer names.

Reset Layer Button This button is used to reset the layer definition to the way it was initially (with the exception of the layer name).

Name Text To change the layer name, type another name in this field.

Action Button Choices are either CREATE or REPLACE.

Type Button Specifies the type of layer to be created or replaced. Choices are POINT, LINE, or AREA. By default, one of these will be selected, but you can change it to either of the others.

Description Text A description for the layer.

On/Off Scale Text Defines the scale at which to turn the layer on and off. The default is 0.

Where Expression Text Specifies the expression to be used to define features for the layer. You can type directly in this field. Invalid expressions are flagged.

Where Builder Button Clicking this button brings up the WHERE window, which allows you to build a valid WHERE expression. When the WHERE window is closed, the resulting expression is displayed in the Where Expression field.

Clear Expression Button Clears the WHERE expression.

Composites Variables List This list contains all the composites that are defined for this import. Selecting a composite inserts it in the layer statement.

Layer Statement Text This is a noneditable text field that displays the layer statement as it will appear when it is sent to the GIS procedure by the import.

***Import Window Fields for Modifying Layers***
Text Fields/Buttons	Type	Use
Layer Names	List	Selectable list of layer names.
Reset Layer	Button	This button is used to reset the layer definition to the way it was initially (with the exception of the layer name).
Name	Text	To change the layer name, type another name in this field.
Action	Button	Choices are either CREATE or REPLACE.
Type	Button	Specifies the type of layer to be created or replaced. Choices are POINT, LINE, or AREA. By default, one of these will be selected, but you can change it to either of the others.
Description	Text	A description for the layer.
On/Off Scale	Text	Defines the scale at which to turn the layer on and off. The default is 0.
Where Expression	Text	Specifies the expression to be used to define features for the layer. You can type directly in this field. Invalid expressions are flagged.
Where Builder	Button	Clicking this button brings up the WHERE window, which allows you to build a valid WHERE expression. When the WHERE window is closed, the resulting expression is displayed in the Where Expression field.
Clear Expression	Button	Clears the WHERE expression.
Composites Variables	List	This list contains all the composites that are defined for this import. Selecting a composite inserts it in the layer statement.
Layer Statement	Text	This is a noneditable text field that displays the layer statement as it will appear when it is sent to the GIS procedure by the import.

The command buttons are used to perform window-wide functions. The [Close] button closes the window and saves all changes that you made. The [Cancel] button closes the window and cancels all changes that you made. The [New] button allows a new layer to be defined. The [Remove] button removes the currently selected layer. The [Help] button accesses the Help system.

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