Each GNSS constellation - depends on which system you're talking about
In the U.S. they're called a GPS constellation
every GPS satellite broadcasts a “navigation message”
navigation message -- broadcast by each satellite
-- contains the information needed to identify ALL the satellites in the constellation
-- contains information needed to compute each satellite's approximate position in orbit
network of ground-based observing stations
constantly tracks the satellites
computes predictive models of each satellite’s orbit.
predicted orbital parameters for a given satellite
recorded in a docuмent called an “ephemeris”
ephemeris ------> plural = “ephemerides”
satellite orbits vary over time
each ephemeris needs to be updated regularly
ground-based Master Control Station performs regular updates of satellite orbits
updated orbits (ephemerides) are transmitted to the GPS satellite constellation
An ephemeris provides the parameters
used to calculate the position of a satellite
along its orbit at any moment in time
An almanac provides the ephemerides
for an entire constellation of satellites
navigation message is broadcast by each satellite
it includes its own ephemeris
this ephemeris is called the “broadcast ephemeris”
updated at frequent intervals
contains the “almanac”
almanac is the less-frequently updated collection of the ephemerides for ALL GPS satellites in the constellation
almanac is updated at much longer intervals
orbital parameters are less accurate in almanacs than the broadcast ephemeris from each individual satellite
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What computes each satellite's orbit information?
What does an almanac provide?
Which is plural, ephemerides or ephemeris?
What do ground-based observing stations do?
What kind of updates does a Master Control Station provide?
Where does a GPS satellite constellation obtain its ephemerides?
Does any particular satellite receive and use all the ephemerides broadcast?
What component sends out a navigation message?
What is used to compose a navigation message?
Why are GPS satellites grouped into constellations?
When a particular satellite leaves Libra and moves into Sagittarius does it change constellations?
What is the almanac a collection of?
Which is updated more often: almanac ephemerides or broadcast ephemerides?
Which is more reliable, almanac ephemerides or satellite signals?
Why bother with a less reliable set of data?
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Sorry for backtracking here but I forgot to say something before that post timed out.
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I was going to add: If anyone can think of additional questions it would be great if you could post them, because I thought of a few later, too.
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The authors are taking us through an overall view first, setting some key cornerstones in place, so that we can more easily grasp the detailed material later on. It is a very well written tutorial and I'm quite impressed that it is open source like this. They could have charged some hard fees for the use of this material.
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It's too bad flat-earthers don't want to know about this stuff. Greater understanding does wonders for your peace of mind.
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But their curiously exclusionary and myopic behavior exemplifies the principle that one firm step into the world of error can mean a complete turn-off to better knowledge of reality and the world around us.
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Those 3 guys taking pictures of the ISS transit of the sun are decidedly immune from the contagion of flat-earthism.
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Topic: Global Navigation Satellite Systems -- tutorial (Read 27714 times)