Text 12925, 61 rader
Skriven 2014-03-18 12:18:04 av mark lewis (1:3634/12.71)
  Kommentar till text 12901 av Joe Delahaye (39489.fidonews)
Ärende: Kyoto anyone?
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On Mon, 17 Mar 2014, Joe Delahaye wrote to TIM RICHARDSON:

 TR> A jumbo jet that travels either either within a country's borders, 
 TR> or transcontinental, ought to have a GPS system that pinpoints its 
 TR> location to within a few hundred feet.

 JD> They have one,  What they do not have, is a GPS transmitter.

exactly... but it doesn't have to be specificly GPS... it only needs to include
the GPS data...

 JD> If memory serves me, GPS will not help a lot over the ocean.  Not 
 JD> enough satelites there to do that.  You need at least 3 satelites 
 JD> to pinpoint a location.  I may be wrong there though regards the 
 JD> number of GEO sats available in sparse areas 

the GPS satellites are not in geosync orbit... they are in constellations and
move around the earth overlapping others' foot prints... yes, a minimum of 3
are needed for basic pinpointing of one's location... more gives better
accuracy... generally speaking, there are 8 or 9 GPS satellites visible for use
at any time and for any point on the earth... the number of visible satellites
can be as high as 12 as they orbit into and out of range...

GPS satellites generally orbit about 20200km (12600mi) and make two full orbits
for each sidereal day... they repeat the same ground tracks each day... there
are 32 (IIRC) satellites in the constellation today...

the information above mainly pertains to the US' NAVSTAR satellites... there
are other GPS satellite constellations in use and being put in place these
days...

  GLONASS - Russia's global navigation system. Fully operational worldwide.

  Galileo - a global system being developed by the European Union and other
            partner countries, planned to be operational by 2014 (and fully
            deployed by 2019)

  Beidou  - People's Republic of China's regional system, currently limited
            to Asia and the West Pacific[136]

  COMPASS - People's Republic of China's global system, planned to be
            operational by 2020

  IRNSS   - India's regional navigation system, planned to be operational by
            2014, covering India and Northern Indian Ocean

  QZSS    - Japanese regional system covering Asia and Oceania


yes, i do track satellites and have written a few private tracking and
prediction packages that make use of the available two-line element (TLE)
files... i also watch the visible ones fly overhead when the sky is clear in
the evenings and mornings ;)

)\/(ark

One of the great tragedies of life is the murder of a beautiful theory by a
gang of brutal facts. --Benjamin Franklin

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