Assigning a Coordinate Reference System

Within GeoHECRAS, every data layer has its own coordinate reference system which is used to integrate it with other data layers within the Map View. Data layers that are constructed with different coordinate reference systems are automatically reprojected to the Map View so that they align with the assigned project coordinate reference system.

To define a coordinate reference system (CRS) for the project, follow these steps:

  1. Select File | Map Coordinates from the ribbon menu.
  2. The Map Coordinates backstage page will be shown.
  3. From the Projected CRS Regions tab, the user can browse to those supported CRS for the location of interest by expanding the continent, country, and then local region. The software will then list all of the coordinate reference systems that correspond to the selected location. Note that some countries straddle the Europe, Asia and Africa boundaries, and are grouped into the Asia, Middle East subregion. Note that countries located in the southwest Pacific Ocean region are grouped into the Australasia continent.
  4. From the Projected CRS Listing tab, the user can browse through all of the supported CRS contained within the software. Once the desired CRS category is found, the user can then expand the category to see all of the listed CRS that correspond to a selected category.
  5. Alternatively, the user can manually enter the region (i.e., state) of interest in the search field and then click on the [Search] button. The software will then filter out only those CRS that correspond to the defined region. For example, entering “Penn” (for Pennsylvania) will only return CRS that correspond to that state.
  6. Single clicking on a listed CRS will show the bounds of the CRS in the Preview window.
  7. Double clicking on a listed CRS will then assign the selected CRS to the project.

Automatic Assigning CRS to non-CRS Data Layers

While assigning the coordinate reference system (CRS) to the project, the Map Coordinates backstage page provides a checkbox option to assign any data layers that do not have a CRS assigned to them to then have the selected CRS assigned to them.

By default, this checkbox is checked (i.e., selected). However, some non-CRS referenced data layers may not lie within the selected project CRS. If this occurs, the software will display an informational dialog box describing this issue for each of the data layers whose coordinates lie outside of the assigned CRS. The user has the option to continue with the CRS assignment for the data layer or skip over it. This can commonly happen to HEC‑RAS models that have not been created in a coordinate reference system. In these situations, it is better to skip over the assignment of the CRS. The data layer may need to be manually georeferenced.

Manually Assigning of CRS to a non-CRS Data Layer

If a data layer has been added to a project and does not have a CRS defined for it, it will display in its own local coordinate reference system. This might happen, for example, when importing an elevation grid data file to the project.

After loading the data layer, only that data layer will be shown in the Map View. The other data layers lie in a different projection of the Map View. The user can then manually assign the project’s CRS to the non-CRS referenced data layer if the data layer coordinates lie within the project’s CRS.

Follow these steps:

  1. Restore the Map View back to one of the other data layers that correspond to the project’s CRS. This can be done by selecting the data layer in the Map Data Layers panel, and then right-clicking and selecting Zoom to Layer Extents from the displayed context menu.
  2. Confirm that the correct CRS has been restored by looking in the lower right corner of the application and examining the CRS that is listed.
  3. After the Map View CRS has been restored, click on the […] properties button for the non-CRS data layer within the Map Data Layers panel. The Properties dialog box for that data layer will be displayed.
  4. Click on the Spatial Reference tab contained within the Properties dialog box.
  5. Click on the [Assign Current CRS] button. This will cause the data layer to be assigned to the Map View CRS. The data contained within the data layer should be visible on the Map View along with the other data.
  6. Click on the [OK] button in the displayed Properties dialog box to finish the process.

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