ENVI Raster

Long name ENVI Image Format
Short name NVI
File extension(s) .hdr
ENVI raster files (.hdr) are supported by GDB for import, update, and export. ENVI data sets consist of two files:
  • the header file (with the extension .hdr)
  • the image file (same basename as the .hdr file, with no fixed extension, but it may be .dat, .img, or .bil, or no extension)

Always use the .hdr file to reference the data set, but the image file is selectable.

Import and export support includes extensive support for projections, including Lat/Long, State Plane, UTM, and other complex projections listed below.

This format provides extensive support for datums and ellipsoids, including:
  • WGS*
  • NAD27
  • NAD83

Most complex projections are imported and exported. Projections that cannot be converted become generic METREs/Arbitrary.

For export, when the projection can be converted to ENVI, the datum is always written.

The following GDB projections can be exported:
  • MSC (Modified Stereographic Conformal)
  • ACEA (Albers Conical Equal Area)
  • AE (Azimuthal Equidistant)
  • EC (Equidistant Conic)
  • ER (Equirectangular)
  • GVNP (General Vertical Near-Side Perspective)
  • GNO (Gnomonic)
  • GOOD (Goode's Homolosine)
  • ISIN (Integerized Sinusoidal)
  • LAEA (Lambert Azimuthal Equal-Area)
  • LAEA_ELL (Lambert Azimuthal Equal-Area)
  • LCC (Lambert Conformal Conic)
  • LONG
  • MER (Mercator)
  • MC (Miller Cylindrical)
  • NZMG (New Zealand Map Grid)
  • OG (Orthographic)
  • OM (Oblique Mercator)
  • PS (Polar Stereographic)
  • PC (Polyconic)
  • RSO (Rectified Skew Orthomorphic)
  • ROB (Robinson)
  • SIN (Sinusoidal)
  • SOM (Space Oblique Mercator)
  • SPCS (State Plane Coordinate System)
  • SPAF (State Plane U.S. Feet)
  • SG (Stereographic)
  • TM (Transverse Mercator (Gauss-Krueger))
  • UTM (Universal Transverse Mercator)
  • VDG (Van der Grinten)

Unsupported projections are exported as ENVI 'Arbitrary' and a Raw projection.

The GDB ENVI format directly supports import of the following ENVI raster types:
  • type 1 (8-bit unsigned integer)
  • type 2 (16-bit signed integer)
  • type 4 (32-bit floating point)
  • type 12 (16-bit unsigned integer)
GDB imports the following ENVI raster types as 32-bit floating point:
  • type 3 (32-bit signed long integer)
  • type 13 (32-bit unsigned long integer)
GDB does not support import of the following ENVI raster types:
  • type 5 (64-bit double precision floating point)
  • type 6 (2x32-bit complex, real-imaginary pair of 32-bit floating point)
  • type 9 (2x64-bit double precision complex, real-imaginary pair of double precision)
  • type 14 (64-bit unsigned integer)
  • type 15 (64-bit unsigned long integer)

Class name and color map information is neither read from, nor written to, ENVI files.

Export of ENVI files is supported. These files are exported with a file type 'NVI'. The exported files can have any number of channels, and may be of any PCI-supported channel type. Exporting multiple channel types will create a raster of a single type that supports all the types because all the channels in an ENVI Raster file must be of the same type. Georeferencing information will be written to the ENVI .hdr file with the limitations mentioned above.

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