On 05/29/2007 08:06 PM, syd & sandy wrote:
>> Well , Ive thought of that too .researching these things leads me to
believe that in real life (I
>> could be wrong),groundspeed is calculated using a nav signal as a
reference point
That's not right.
Groundspeed is groundspeed. There's only one proper definition of
groundspeed.
An _approximation_ to groundspeed in terms of the rate of slant range
made good to/from a navaid is sometimes encountered, for example in a
_DME_ unit. This is considered a nonideality of the DME system, not
a redefinition of groundspeed.
This nonideality is never AFAIK exhibited by GPS or RADAR units. Every
GPS and every RADAR I've ever seen or heard of, when asked to report
groundspeed, reports honest-to-goodness groundspeed, independent of any
route, independent of the relationship between the ground track and
this-or-that navaid.
> > , so it is only
> > accurate if you are flying directly toward that point... But a
/velocities/groundspeed could be
> > used as a starting point ...
It takes only a couple of lines of nasal to calculate the groundspeed
in terms of the already-available properties. Hint:
Aircraft/A-10/Nasal/aar.nas line 261
... so I don't understand what the discussion is about.
The Subject: line refers to groundspeed. If you want to ask about
something else, perhaps about ETE or ETA at this-or-that station,
then the answer might become route-dependent. (Different questions
have different answers!)
So: If there's a problem here that needs solving, please describe
the problem more fully.
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