Georeferencing Sources

When the GeoHECHMS software imports a HEC-HMS model, it automatically places the source on the Map View. However, if the original HEC-HMS model was not spatially georeferenced, the source will not align with any loaded background base map. While the software can operate without any issues in this situation, the user may prefer that the source be georeferenced to the background base map. Therefore, it may become necessary to georeference the imported HEC-HMS source.

The Georeference Sources command is used to manually georeference each of the sources to the background base map displayed in the Map View.

Follow the steps below to use the Georeference Sources command:

1. From the Input ribbon menu, click the Sources dropdown menu and select the Georeference Sources
   
2. The Georeference Sources dialog box will be displayed.
   

The following sections describe how to georeference a source to a desired location and interact with the above dialog box.

Selecting Source to Georeference

The Select Source to Georeference section allows the user to select the source that is to be georeferenced. The user can select the source present in the HEC-HMS model from the Source ID dropdown combo box. Alternatively, the user can click the [Pick] button to select the source from the Map View.

After clicking the [Pick] button, the dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user on what to do next. The user can then interactively select a source from the Map View.

Note that the user can select only one source at a time to georeference.

Upon selecting a source, the dialog box will be redisplayed, and the Source ID dropdown combo box updates automatically to match the selected source. The user can unselect the source using the [Clear] button.

Snapping Source to an Alignment Point

If an existing alignment point for the source exists on the Map View, the Snap to Alignment Point option can be used to snap the HEC-HMS source to the alignment point.

The user can click the [Pick] button to select the alignment point from the Map View. On clicking the [Pick] button, the dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user on what to do next. The user can then interactively select the alignment point from the Map View.

Upon selecting the point, the user is immediately returned to the dialog box, and the status of the Select alignment point read-only field changes to Selected. The user can select only one alignment point to use for georeferencing. The user can unselect the alignment point using the [Clear] button.

Once the alignment point is selected, the user can click the [Snap] button and the software will snap the selected source to the alignment point.

Drawing Source Node on Map View

The Draw on Map View radio button option allows the user to draw a source node on the Map View to which the selected source is to be georeferenced.

Selecting the Draw on Map View radio button option enables the [Draw] button. The user can click the [Draw] button to interactively draw a source node on the Map View.

On clicking the [Draw] button, the dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user on what to do next. The user can then draw the source node on the Map View. Once the source node is drawn, the dialog box will be redisplayed, and the selected source will be georeferenced to the drawn node.

Assigning Source Elevation

The Assign Source Elevation section uses the elevation data to assign an invert elevation to the georeferenced source. The user should define the data in this section before georeferencing sources. Alternatively, the user can use the Assign Sources Elevations command to assign invert elevations to the already drawn sources. Refer to this article in our knowledge base to learn more about Assign Source Elevations command.

For assigning elevation data, this section supports the following terrain elevation source types:

The following terrain elevation source types are unsupported:

The user can also apply an elevation offset to raise or lower the selected source by the specified amount by checking the Apply elevation offset option. On selecting this checkbox, the entry field next to it becomes available for entering an elevation offset value.