The Merge Land Use command of GeoHECHMS allows the user to merge two or more land use layers into a single land use layer.
Having multiple land use layers may create issues during the course of a modeling exercise, which is why the user may want to merge multiple layers together into one integrated surface layer. For example, although one land use layer could contain the general area map coverage created using the Classify Land Use command, this command will not likely capture an accurate land use map of an urban area contained within the area being processed. Under these circumstances, the user would be advised to use the Draw Land Use command. However, since the Classify Land Use command already analyzed the entire area, the user would not be able to use the base map and “draw” regions of different land use polygons within the urban area. In this situation, the solution would be for the user to create two land use layers—one layer that was created using the automated Classify Land Use command and another layer that was more detailed and developed manually using the Draw Land Use command. The user can then use the Merge Land Use command to merge these two layers.
Follow the steps given below to merge two or more land use layers using the Merge Land Use command:
- From the Input ribbon menu, select the Merge Land Use command.
- The Merge Land Use dialog box will be displayed.
The following sections describe how to interact with the above dialog box.
Select Land Use Layers to Merge
This section controls the selection of land use layers to be merged into a single layer.
From the Existing land use layer dropdown combo box, select the land use layers, one at a time, which need to be merged and click the [Add] button. The selected land use layer will be added to the table listing the land use layers to be merged.
To change the merge order of the listed land use layers, select the appropriate row and right-click to display a context menu. Then, select the Move Layer Up or Move Layer Down context menu command to change the merge order of the highlighted land use layer. Layers that are higher in the listing have precedence over layers that appear lower in the list.
Merged Land Use Layer Limits
This section allows the user to define the rectangular extents of the merged land use layer using the criteria described below. The following options are available to define the rectangular extents of the merged land use layer:
- Land use layer limits: The merged land use layer will have the same extent as the original source data.
- User-defined limits: The user can draw the rectangular extents of the merged land use layer to correspond to a specific area defined by the user. This can make the merged land use layer smaller and easier to work with. Click the [Pick] button to define the limits of the land use layer. The dialog box will temporarily disappear, and an information message will be displayed on the status line. Click and drag a rectangular region to define the limits of the merged land use layer. After releasing the mouse, the user will be returned to the dialog box. A layer will be created with a rectangular box to represent the user-defined selected region.
- Clipping polygons: The user can select one or more land use polygons and the software will clip the selected land user layer to the boundary of the polygons. The software will set the limits of the layer to the extents of the selected polygons. Clicking the [Pick] button causes the dialog box to disappear, at which point the user is then prompted to select land use polygons. After selecting the polygons, the user is immediately returned to the dialog box. The software then displays the total number of selected polygons in the dialog box.
- HEC-HMS model extents: If a HEC-HMS model has been defined, this option will create a bounding rectangular region to correspond to the extents of the defined model, plus an additional buffer boundary.
Land Use Processing Specifications
This section allows the user to specify the new land user layer name in the Merged land user layer entry field.
Merging the Land Use Layer
After the options have been defined, click the [Merge] button and the software will merge the land use layers into a new land user layer and load the layer into the Map Data Layers panel.