On 6/19/2013 11:50 PM, JustWaitAFrekinMinute wrote:
On 6/19/2013 10:39 PM, Hank© wrote:
On 6/19/2013 10:29 PM, wrote:
On Wed, 19 Jun 2013 21:01:14 -0400, " Sir Gregory Hall, Esq·"
åke wrote:

wrote in message
...
Using a Garmin's Waypoint Projection feature, and projecting a
waypoint at 90 degrees, shouldn't my projected waypoint end up on the
same latitude as the original? And if not, why not?

For example, beginning at 30 degrees N latitude and 89 degrees W
longitude, I project a new waypoint at a distance of 10 miles with a
bearing of 90 degrees. As expected, my projected longitude changes to
a point further east. But for some reason, the projected latitude
ends up at a higher latitude than 30 degrees. In my example, the
projected latitude ends up as 30 degrees, 23.866 Minutes North.

I've tried using the same example on 3 different Garmins with the same
result. What am I missing?

I suspect it's a matter of choosing the right Datum.
http://geography.about.com/od/geogra...n/a/datums.htm
The above should explain it well enough.
Your direction is only as accurate as the datum chosen.

My unit has 110 different Datums to choose from. So far, I've just
always used the Garmin default (WGS 84) for navigation and it has
always been fine for that. The waypoint projection feature is the only
thing that seems a bit squirrely. So if you have a datum
recommendation that might cure that, I'll be glad to give it a go.

If you correct for deviation your course heading will be 090 true.

Is there a static equation for that?

No. But the link I provided will tell you the exact magnetic deviation
for any position at any given time.