Adding an Elevation Layer

GeoHECRAS can construct an elevation terrain surface from online elevation data sources or through a local elevation data file.

Adding Online Elevation Data

GeoHECRAS can utilize elevation data directly from either the USGS or NASA elevation data servers:

  • US Elevation (10m) – USGS: Accesses the elevation data from the USGS National Elevation Dataset (NED) data server. Elevation data with a resolution of 10m confined to the area within the borders of the United States. Different parts of the United States have different elevation resolutions. The National Elevation Dataset (NED) is the primary elevation data product of the USGS, and is a seamless dataset with the best available raster elevation data of the conterminous United States, Alaska, Hawaii, and territorial islands.
  • World Elevation (30m) – NASA: Accesses the elevation data from NASA elevation data server. Elevation data with a resolution of 30m, derived from the Shuttle Radar Topography Mission (SRTM) data. Different parts of the world have different elevation resolutions. The SRTM obtained elevation data on a near-global scale to generate the most complete high-resolution digital topographic database of Earth. The SRTM consisted of a specially modified radar system that flew onboard the Space Shuttle Endeavour during an 11-day mission in February 2000.

To add the online elevation data from the USGS or NASA Elevation Data Server:

  1. Right-click on the Map Data Layer panel and select Add Elevation Layer from the displayed context menu.Select Add Elevation Data
  2. The Add Elevation Layer dialog box will appear.
    Online Elevation Data dialog box
  3. Select the Online Elevation Data tab.
  4. Check the Use online elevation data source checkbox.
  5. Click the [OK] button.
  6. The software will start to pulling elevation data tiles from the selected elevation data source and construct an elevation terrain surface.
  7. Alternatively, you can download the data onto the local computer as an elevation grid DEM. Choose the Download Elevation DEM tab. You can then specify the boundary limits and where the DEM file should be saved.
    Online Elevation Data dialog box

Adding Local Elevation Grid Data

GeoHECRAS supports most major elevation grid data file formats, such as:

  • ArcInfo ASCII Elevation Grids
  • ArcInfo Binary Elevation Grids
  • GeoTIFF Elevation Grids
  • USGS DEM Elevation Grids
  • USGS NED Elevation Grids – BIL Format
  • USGS NED Elevation Grids – Float Format

To add elevation data using a local elevation grid data file:

  1. Right-click on the Map Data Layer panel and select Add Elevation Layer from the displayed context menu.Select Add Elevation Data
  2. The Add Elevation Layer dialog box will appear.
  3. Select the Local File Elevation Data tab.
    Online Elevation Data dialog box
  4. Click on the […] file browse button and select the elevation grid data file to load.
  5. Click the [OK] button.
  6. The software will load the elevation grid data file as an elevation terrain surface.

Using Other Elevation Data

Other local elevation data files can be processed within the software to create an elevation terrain surface. This includes:

  • ArcInfo Contour Shapefiles
  • ArcInfo Elevation Point Shapefiles
  • ArcInfo GDB File Geodatabases
  • ArcInfo MDB Personal Geodatabases
  • AutoCAD Civil 3D Terrain Surfaces
  • AutoCAD Contours
  • Bentley MicroStation Terrain Surfaces
  • Bentley MicroStation Contours
  • LandXML Terrain Models
  • XYZ ASCII Point Terrain Data

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