A Digital Elevation Model (DEM) is a representation of the bare ground (bare earth) topographic surface of the Earth excluding trees, buildings, and any other surface objects. 

Legacy DEMs were produced from cartographic contours derived from hand-drawn topographic maps. 

USGS DEMs were replaced by NEDs (National Elevation Dataset) in 1999.

• Complete Coverage of the Continental US in 30 or 60 Meter resolutions
       Models contain ODB level 1 / 2 data.
  
  
• Models all voided and slivered areas filled
  
  
• Quads are made rectangular data sets to be compatible with ChartTiff Topographic Maps
  
  
• File names compatible with USGS DRG Quad naming standard
  
  
• Horizontal Resolutions Available
  
  • 30 Meter (1 Arc Second) resolution for Continental US
  • 60 Meter (2 Arc Second) resolution for Continental US
        Generated from the 30-Meter DEMs
  
  
• Vertical Datum: 1929 (NGVD 29)
  
  
• USGS DEM (Digital Elevation Model) format documentation:
  
  • Click here to download 1DEM0897 standard in PDF format
  • Click here to download 2DEM0198 standard in PDF format
  • Click here to download 3DEM0897 standard in PDF format
  • Click here to download PDEM0198 standard in PDF format


• Creation Date from Metadata file included in ChartTiff's Order.txt file.
  
  
• Order by:
  • Individual Quads


• Formmats Available:
  
  • USGS Standard DEM file format
  • GeoTIFF Format, includes ".tfw" world file
  • ESRI Grid Float Format
  • PLS-CADD ASCII Text, X,Y,Z format
        XYZ text file format specifically for PLS CADD Software
  • ASCII Text, X,Y,Z format
        XYZ text file format is a simple text format
        where each elevation point is described by x, y, and z coordinates.
        The x value defines the east/west coordinate,
              y defines the north/south coordinate, and
              z defines the elevation.
        User can select Tab, Comma or Space delimited file.
        The XYZ text format does not contain any header information:
    
               x1,y1,z1
               x2,y2,z2
               x3,y3,z3
               .....
               xn,yn,zn
  • C Tech File Format
        GMF and EFF files, directly read by C Tech Software
  
  
• Available Projections
  • UTM - User Selectable Zones - NAD27 / NAD83 / WGS72 / WGS84
  • State Plane - User Selectable Zones - NAD27 / NAD83
  • Latitude / Longitude - NAD27 / NAD83 / WGS72 / WGS84
  • Web Mercator - WGS84


• Optional Shaded Elevation Models can be added as an additional file.
  Click Here for Additional Information.
  


• A DEM Quad is available as 1 Free Download