Generating spot heights on DEMs

The Generate Spot Heights tool creates spot heights based on one or more digital elevation models (DEMs). A wizard guides you through the spot height generation process, allowing you to configure several options including where to store the generated spot heights and in which field to store the z-values for the spot heights.

A DEM contains the information used to derive the spot heights but may not cover a large area of interest. When more than one DEM is selected, a mosaic is created so there is a single elevation model.

Once the DEMs are selected, a grid is created to define the density of the spot heights generated. The grid can be created in memory during the spot height generation process, or you can use a polygon feature class as the grid. When a grid is created in memory, you can specify the number of rows and columns it is going to contain. When a grid is based on a feature class, you can use a polygon grid or other feature class that contains polygons.

After the spatial grid is defined, the method used to generate the spot heights can be selected. For each cell of the spatial grid, you can specify what points to generate.

Pasos:

1. Start ArcMap.
   Sugerencia:

   If the ArcMap - Getting Started dialog box appears, you can open a new or existing map document. You can also check the Do not show this dialog box in the future check box and click Open.

2. Load a DEM in the table of contents.
3. Add the Generate Spot Heights tool in ArcMap by doing the following:
   1. On the main menu, click Customize > Customize Mode.

      The Customize dialog box appears.

   2. Click the Commands tab.
   3. In the Categories list, choose Production Contour Tools.
   4. From the Commands list, drag the Production Generate Spot Heights tool to a toolbar.
   5. Click Close.
4. On the main menu, click Customize > Toolbars > Production Editing.
5. Click the Production Start Editing button on the Production Editing toolbar.
   Nota:

   The Manage Features and Create Attributes, Update Attributes, or Metadata Attributes windows automatically appear when you start an edit session using the Production Start Editing tool.

   Sugerencia:

   If the Create Attributes, Update Attributes, or Metadata Attributes window does not appear when you start an edit session, click the Link Feature Manager To Attributes Window button on the Manage Features window.

6. Click the Generate Spot Heights button .

   The Layer Settings dialog box appears.
7. Click the Spot Height Layer arrow and choose the point feature class in which you want to store the spot heights.
8. If necessary, click the Elevation Field to Update (optional) drop-down arrow and choose a field in which to store the z-values.
9. Click Next.

   The DEM Settings dialog box appears.
10. Choose the DEMs you want to use to derive spot heights from the DEM Layers list.
Nota:

You can choose multiple DEMs by dragging or by holding the CTRL or SHIFT key and clicking the DEM names.

Sugerencia:

You can run the process on a single DEM and append the spot heights to an existing layer. This may be more efficient than creating a mosaic of many DEMs and generating the spot heights.

11. If you are using more than one DEM, you can change the default name and location of the output mosaic by clicking the ellipsis button (...) next to the Output Mosaic Location field.
12. To delete the mosaic once the process is complete, check the Delete output mosaic check box.
13. Click Next.

    The Spatial Grid Settings dialog box appears.
14. Choose an option in the Spatial Grid Options area.
    • Create an in-memory spatial grid—The spatial grid is created during the spot height generation process based on the number of rows and columns specified.
    • Use existing feature layer as spatial grid—The spatial grid is created using an existing polygon feature class.
15. If you want to create an in-memory spatial grid, do the following:

    To create a grid using an existing feature class, proceed to step 16.

    1. Type a value or use the arrows in the Spatial Grid Rows box to define the number of rows the grid is going to have.
    2. Type a value or use the arrows in the Spatial Grid Columns box to define the number of columns the grid is going to have.
16. If you want to create the spatial grid using an existing feature class, do the following:
    1. Choose the Use existing feature layer as spatial grid option in the Spatial Grid Options area.
    2. Click the Select Spatial Grid Layer arrow and choose a feature class to use as the grid.
17. Click Next.

    The Spot Height Generation Mode dialog box appears.
18. Choose an option in the Spot Height Generation Mode area.
    • Generate Highs and Lows—Generates two points for each spatial grid cell or polygon using both the highest and lowest pixel values from the DEM
    • Generate Highs Only—Generates one point for each spatial grid cell or polygon using the highest pixel value in the DEM
    • Generate Lows Only—Generates one point for each spatial grid cell or polygon using the lowest pixel value in the DEM
19. Click Finish.

The spot heights are created for the DEMs you have chosen, and z-values are populated based on the options defined in the wizard.