GeoHECRAS fully supports both Metric (SI) and US units.
Default Project Units
The software will auto detect the country that the computer is located in. If the computer is located within the United States, it will default to US units. If the computer is located outside of the United States, it will default to metric (SI) units.
The units are defined in the Options backstage page. Select File | Options to view the Options backstage page. The default units can be overwritten by the user.
Importing HEC‑RAS Models
An imported HEC‑RAS model defines the project’s units. For example, even if the default project units are US, importing a metric HEC‑RAS model will set the project units as metric.
If other data (e.g., shapefiles) have already been loaded that are in a different unit system than the HEC‑RAS model, then the software will display a confirmation dialog box when importing the HEC‑RAS model. This confirmation dialog box will inform the user that the loaded data and the HEC‑RAS model are in different unit systems, and will ask if it should continue with the HEC‑RAS import process.
HEC‑RAS Model Unit Conversion
GeoHECRAS will not perform unit conversions (i.e., US to Metric, Metric to US) of HEC‑RAS models. However, the software will perform unit conversions and reprojections of GIS and elevation data.
Coordinate Reference Systems
Note that the selected Coordinate Reference System (CRS) should match the units to be used in defining the HEC‑RAS model data. See this section for more information on assigning a coordinate reference system.
Most countries use either a period (.) or a comma (,) symbol as the decimal separator in numbers; each country has adopted a standard for which decimal separator symbol is to be used. Unfortunately, the HEC‑RAS analysis engine requires that the period be used as a decimal separator.
If something other than the period is being used as the decimal separator, the correct decimal separator can be selected within Microsoft Windows. From the Windows Control Panel, select Region and Language. Windows will display the Region and Language dialog box. Select English (United States) as the format.