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Clipping Layers

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Existing layer(s) can be clipped against shapes (polygons) defined in an area layer. Typically a selection set is used to select the area features that form the clipping polygon. Maptitude has two functions to do this. Clip by Area is the simplest and clips one layer. In contrast, the Multi Clipper is capable of clipping all layers in the current map, and creating a new map from the clipped layers.

To use either method, you should probably create a selection set that defines the clipping polygon. In the example below, we use the County layer but use a selection set to create a clipping polygon from one feature (Harris, TX). To clip a single layer, set the layer to be the working layer and then select Tools->Geographic Utilities->Clip by Area from the main menu. This will display the Clip by Area dialog box:

The Clip by Area dialog box (set to clip the Highway layer to the Harris County selection set)

The Clip by Area dialog box (set to clip the Highway layer to the Harris County selection set)

Use the Layers tab to specify the layer and selection set that will be used to define the clip polygon (Harris County from the County layer). Set the Add layer to map if you wish to create a copy from the clipped layer. If you clear this checkbox, the existing layer will be replaced by the clipped layer. This is not recommended. Use the Attributes and Node Attributes tabs to define which attributes should be copied to the new clipped layer. Press OK to start the clip operation. Here are the results:

The Highways layer clipped to the Harris County polygon (note: the original unclipped Highways layer has been hidden)

The Highways layer clipped to the Harris County polygon (note: the original unclipped Highways layer has been hidden)

Here, the Highways layer has been clipped to the Harris County area. A copy was created (Highway/Freeway:1) and this is displayed. The original Highways layer has been hidden so that the smaller clipped layer is visible.

To use the Multi Clipper, select Tools->Geographic Utilities->Multi Clipper on the main menu. The resulting Multi Clipper dialog box lets you choose which layers to clip. Instead of an Add layer to map checkbox, there is an Options radio button. You can still choose to add the clipped layers to the current map (i.e. duplicating the original layers), but you also have the option to Create new map from the clipped layers. This latter option is generally easier to manage.

Masks are a less destructive alternative to using the multi clipper. Instead of destroying the features outside of the desired area, masks simply cover the unwanted areas up. This is ideal for presentations.

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