Overlay a Geo-referenced Map on a Digital Elevation Model in 3D View

This section will guide how to load a satellite geo-referenced map from Google Earth to cover the surface of a DEM (topo) in 3D View of EFDC_Explorer 10.

This guidance will take the demo model DM-13 as an example because it is available on EEMS resources. The instruction is mostly presented in the EEMS 3D View.

Generate DEM file

Load the DM-13 model, open the 2DH View, select Generate DEM option from the Layer Control as shown in Figure 1.

Figure 1. Generate a DEM option from Layer Control in 2DH View.

Once the option is selected, the Generate DEM form will appear as shown in Figure 2. From this form, the user can click on Add File then browse to the digital elevation data file (terrain*.xyz) from the Data folder. Once loaded, the coordinates of the Lower-Left and Upper-Right points will be updated as well as the Cell Size and Number of Cells, the user can change the Cell Size then click on the Calculator symbol to update the Number of Cells and vice versa. The more cells the higher resolution of the DEM file. The output format for the generated DEM files is TB2, click the Generate DEM button to start generating DEM file.

Figure 2. Generate DEM form.


Once, the Generate DEM button is selected, the Export DEM form is displayed as shown in Figure 3. Enter a name in the File Name (e.g DEM), select the folder directory to store the file then click Save button as shown in Figure 3.

Figure 3. Export DEM to a file.



Load a DEM file in 3D View

Open the 3D View, click the Import External Layer in the Layer Control.  The Open External Layer form will be displayed. Select the DEM data file from the drop-down list next to the File Name box as shown in Figure 4. Select the DEM.tb2 in the Data folder then click Open button. The DEM layer will be added to the Layer Control and displayed as Figure 5.

Figure 4. Import DEM file.


Figure 5. DEM displayed in 3D View.

The Figure 5 shows the model grid is not fit to the DEM. To fix this issue, RMC on the DEM layer on the Layer Control, then select Properties option as shown in Figure 6

Figure 6. RMC the DEM layer in 3D View.

The DEM Layer Properties form will appear as shown in Figure 7, click on Flip button then click OK button.

Figure 7. DEM properties.

The user can adjust vertical exaggeration to having a better view by changing the Vertical Scale Modifier in the DEM Layer Properties form as shown in Figure 7 and in the form of 3D View Settings by RMC on the legend as shown in Figure 8.

Figure 8. 3D View Settings.

Use Overlay Image

This option allows using a geo-referenced map (e.g Google satellite image) to cover the surface of the DEM. Checked on the box of Use Overlay Image then click Browse button to browse to the geo-referenced image as shown in Figure 9, select map_geo.jgw file in the Map-Images folder then click Open button and result is shown in Figure 10.


Figure 9. Use the Overlay Image option.


Figure 10. DEM covered with a satellite image.