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In article <164dc8ce.0202181043.7bbd52bc@posting.google.com>,
JP <jp@jphudson.com> wrote:
>While loading the way points into my Garmin 295 (back up), I noticed
>there are differences of 2 to 6 degrees between the GPS headings and
>the chart depicted, mostly at VOR out-bound and dog-leg intersections.

You don't need GPS for that! Find any VOR that's out of alignment that
has an airway leading to one that's been adjusted more recently. UBG
to CVO (V495) has you going out on the 174 radial of UBG and arriving
on the 357 radial of CVO. And no, that's no dog leg! I suppose a long
enough airway (as a function of great circle distance taking into account
distance from the magnetic north pole) would show this effect for two
perfectly aligned VORs. Someone could probably explain how airway design
takes this into account.

The GPS is going to pretend all VORs are perfectly aligned (based on its
idea of magnetic variation). You'll still get to the right place because
the GPS should have actual waypoints for the intersections on dogleg
airways. It's not using a database of VOR radials to compute them. You
could get in trouble if you tried to manually create routes by using
radials off of VOR waypoints without compensating for any misalignment.
You can find out what variation a navaid is aligned to by looking it
up in the AFD (?) or online on www.airnav.com. UBG, for example, is
aligned to 21E (as of 1965) when it is closer to 19E. CVO is aligned
to 18E (as of 1995) which explains the 3 degree difference.

--
Ben Jackson
<ben@ben.com>
http://www.ben.com/

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