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USGS CMG "Navigation" Definition

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    This documents InfoBank's usage of "navigation".
  • "Navigation" (as used within the CMG InfoBank ) is the position of a platform at a specific time.

  • The position is commonly a latitude, longitude pair.

  • UTM x/y coordinates are sometimes used.


Latitudes and longitudes
  • Latitudes are parallel to the Equator and range from -90 degrees (South Pole) to+90 degrees (North Pole).
  • The northern hemisphere has positive latitudes.
  • The southern hemisphere has negative latitudes.
  • Longitudes are perpendicular to the Equator are range from -180 degrees (International Date Line) to +179.99999... degrees (just west of the International Date Line).
  • Under this convention -- the western hemisphere has negative longitudes and the eastern hemisphere has positive longitudes.

  • UTM x/y coordinates are a rectangular coordinate system with units in meters from the equator (the "y" value) and meters from a central meridian (the "x" value).
  • The central meridian defines a 6 degree wide zone.
  • The zone must beknown for uniqueness.
  • Zone 1 starts at the International Date Line, has a central meridian 3 degrees counterclockwise around the earth from there (-177d), and continues another 3degrees.
  • Zone 2 has a central meridian of -171d (-177 - 6), and so on around the globe.

Derivative information
  • Course, speed, distance, and Eotvos are derived from pairs of positions and their associated times.

  • Navigation information occurs in the InfoBank as:
    scattered < Activity-ID >.0# or <Activity-ID>.6# files containing time sequential information.
    analog physical records, usually electrostatic or photostatic rolls
    metadata information about navigation analog paper rolls, inventory of gear, deployment of gear, operation of gear, magnetic tapes and floppies, paper printer listings, and platform movements.

    • A "time" key is associated with each record for correlation with other scattered information datasets.

    "We will be known by the tracks we leave behind." -- Dakota proverb

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    Page Last Modified: Mon Nov 4 03:37:31 PST 2013  (chd)