Earth Reference Models (ERMs)

• Earth’s shape

  • Sphere: Used by meteorology community (see JMCDM).
  • Ellipsoid: 21 (as per NIMA TR 8350.2).
  • Mathematical approximations are not the earth.
  • ERMs do not include the natural environment (smooth surfaces).

• Horizontal Datum

  • 200+ (as per NIMA TR 8350.2)
  • Common interoperability problem in C4ISR community

• Vertical Datum

  • Many ...
    • Earth Reference Model (i.e., sphere/ellipsoid)
    • WGS-84 Geoid
    • MSL (local)
    • Others (e.g., NAVD-88, EGM-96)
  • Interoperability problem in littoral regions.

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