Re: [Paddlewise] Garmin 12XL GPS unit: Navigation

At 01:05 PM 6/23/98 -0500, you wrote:
>(major snips. . .)

>The Garmin GPS 12XL has an amazing array of features, but what they are
>and how to use them is not intuitive, and the organization of the manual
>is hardly a model of clarity. My best recommendation is to sit down with
>the manual and 12XL at home and practice everything in the manual until
>you have a good grasp of the 12XL's operation. Then preload it with
>meaningfully named waypoints before you set out.
>
	I've gone so far as to estimate coordinates by taking a reading from a
position while I was due north of an objective location and then taking
another reading  when due west of the objective. I was looking for a small
lake (fly fishing) in the Mt. Hood Nat'l Forest and kept getting lost on
the logging roads, which branch out in all directions. 

	My map shows locations and roads, but the legend is marked in township
grids. . . By taking coordinates from north and east positions according to
a detailed contour map, I was able to approximate the location of my
lake/road intersections. Then once out on the logging roads that wind all
over and all seem to be designated "FS 1210," I was able to keep a fix on
my position relative to the estimated location of my turn off. . . 

	How close did I estimate my coordinates to the turn off? About 100 feet. 

	My next application is to locate my launch site coordinates on a chart
that lacks lat. and long. designations. (Don't these chart makers navigate?
!!!) Then I haul out my dividers and parallel rules to measure distance to
my objective. 

	In my hypothetical example the objective (C) is north and east of my
launch site (A). So I calculate distance in nautical miles due north of the
launch to a point perpendicualar to my objective (B). Then, distance in
nautical miles due east from point (B) to my objective (C). 

	Now I have a right triangle with known (calculated) distances: (A to B),
and (B to C). 

	Here's the tricky part: David Burch in "Kayak Navigation" notes that
nautical miles correlate to degrees, minutes, and seconds of Latitude.
Longitude gets problematic at polar extremes, but I'm at 45.00 parallel
more or less. . . And I'm looking for the landfall of an ISLAND, not a dock
on the island. 

	Accordingly, it's possible to estimate the coordinates of the objective
(C) by converting nautical miles (A to B) and (B to C) into degrees,
minutes, and seconds. Pythagorus will give you the distance of your
diagonal (A to C), but the Garmin 12 series will calculate it for you
through the "GoTo" function.

	From this data, it's possible to set up way-points on a map and then track
your route as you navigate around islands, navigation lanes, etc. The
Garmin will ALWAYS provide bearing and distance from your current location
to your destination (along with speed, estimated time of arrival, estimated
time enroute, sunrise/sunset at your location, time of day, speed made
good, cross track error. . .) 

	Toys!!! Gotta love 'em!!! Geo./Svenn



______________________________
George Bergeron, Secretary '99
Oswego Heritage Council
www.europa.com/~heritage/
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