The Elevation (DEM) function (
) makes it possible to import geospatial elevation data from digital elevation models (on the DEM file format using the USGS standard from the United States Geological Survey) and map the elevation data to a function of x and y. A DEM file contains elevation data for a portion of the Earth’s surface. The resulting function behaves essentially like a grid-based interpolation function. The default Function name is elev1.
) makes it possible to import geospatial elevation data from digital elevation models (on the DEM file format using the USGS standard from the United States Geological Survey) and map the elevation data to a function of x and y. A DEM file contains elevation data for a portion of the Earth’s surface. The resulting function behaves essentially like a grid-based interpolation function. The default Function name is elev1.Enter the path and name of the elevation file in the Filename text field, or click Browse to select a DEM file with elevation data in the Elevation Data dialog box. When a DEM file is open, the File section displays the coordinates for the southeast corner.
Click Import to import the elevation data in the specified DEM file into the model; otherwise, COMSOL references the elevation data on your file system. When the elevation data is imported, the File section (under Data imported into model) contains information about the filename and the location for the data. Click Export to save the elevation data to a file and reference from that file instead of including it in the model. Click the Discard button to delete the imported data from the model.
For interpolation in the elevation data, select an Interpolation method from the list: Nearest neighbor or Linear (the default).
For extrapolation of values that are outside the range in the elevation data, select an Extrapolation method from the list: Constant (the default), Linear, Nearest function (which evaluates the function from the closes grid point at the actual point where a value is requested), or Specific value. For a Specific value, enter a value to Replace missing data with field (SI unit: m). The default is 0 m.
On the Settings window toolbar, click the Create Surface button (
) to add a Parametric Surface node to represent the elevation function as a parametric surface in the Geometry branch for 3D models.
) to add a Parametric Surface node to represent the elevation function as a parametric surface in the Geometry branch for 3D models.