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Elevation Layers

VTBuilder will read in elevation files and save them to a simple binary terrain format (BT). You can load multiple files, merge them, and select the area of interest to export.

VTBuilder can import elevation from these formats:

• USGS DEM (Digital Elevation Models)
• SDTS DEMs
• several less-common flavors of DEM
• GTOPO30
• DTED0
• CDF (preliminary)
• PGM ("portable graymap format")
• Surfer 7 Binary Grid
• TerraGen terrains
• ArcInfo Ascii Grid (preliminary)

Both 1-degree (geographic) and 7.5-minute (UTM) DEMs are supported.  If UTM DEMs cross a zone boundary, VTBuilder can convert them to the same zone for you.

The native format for elevation is the BT format.  BT can be read by VTP Enviro program and other

Display of Elevation Layers

The default is to display elevation as artificially shaded and false-colored by elevation.  Elevation at sea level is shown in blue.  Areas of unknown elevation are shown in red, unless hidden with the View: Hide Unknown Areas option

How To Resample and Export Elevation

• Use the Area Tool to drag the black lines with the mouse to indicate the area of interest.  You can also type in precise extents with the command Export Area - Numeric Values
• Use the command "Elevation - Merge and Export Elevation" to create a BT file
• Important!  If you will be using this for terrain LOD in Enviro (recommended), let VTBuilder enforce the size constraints in the "Merge and Resample" dialog.

Elevation Menus

• Elevation
  • Select Elevation
    • Use this mode to pick elevation layers with the mouse.
  • Remove terrain above sea
    • For the currently selected layer, sets all elevation points which are above sea level to 'unknown' (shown as red)
  • Fill in unknown areas
    • For the currently selected layer, this feature can be used to fill "cracks" of unknown values.  The unknown areas are filled in by interpolating the surrounding known areas.
  • Scale Elevation
    • For the currently selected layer, scales the elevation values up or down.
  • Export to TerraGen
    • Saves the current elevation layer to a TerraGen file.
  • Merge Area and Save to BT
    • Asks you for an output filename, merges and resamples all elevation within the Export Area into a new BT file.
• Export Area
  • Set to Extents
    • Moves the black lines to surround all of the currently loaded terrains.
  • Numeric Values
    • Allows you to examine and manually enter the range of the export area.
  • Export Bitmap
    • Creates and saves a bitmap (BMP) of the Export Area.  The current terrain layer will be used to provide artificial color and shading for the bitmap.  When you don't have any imagery for your area, only elevation, this can give you a visually useful image - similar to the "Texture: Derive from Elevation" option in Enviro, but better because the image is generated before runtime.