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From: Chuck Holst <CHUCK_at_multitech.com>
subject: [Paddlewise] Using a GPS unit
Date: Tue, 23 Jun 1998 13:05:45 -0500
 -----Original Message-----
From: Sisler, Clyde [mailto:Clyde.Sisler_at_wang.com]
Sent: Tuesday, June 23, 1998 10:42 AM
To: 'Paddlewise'
Subject: [Paddlewise] Freeport, ME

<snip>
High tide on Friday was about 7 and that was when I took off.  I had a 4
hour window on the tide to get back in so that was no problem.  This was
to be my navigation day and I plotted a course from island to island the
night before.  The idea was to see how well I did and use the GPS to
identify the coordinates, which I wrote down and would use tomorrow to
re-trace the course with GPS GoTo commands and everything went pretty
much as planned.  The key for me was to make sure I knew exactly where I
was at all times.  I really only had one problem and it took me about 30
minutes to confirm I really was in the place I thought I was.

<snip>

I got the GPS 12XL manual out to see how to GoTo the coordinates I had
written down faithfully during the day and found out you can't.  I
didn't save them because each waypoint is assigned a sequential number,
which by themselves are meaningless.  You can give each waypoint a name
but that is too time consuming.  It appears the only thing you can enter
manually is a bearing and distance and I wasn't going to do all that.
Bummer.  Well, I'll know better next time.

<snip>

**********************************************************************

If you can get coordinates off a map, the best way to use your GPS
12XL is to program the coordinates of your put-in, destinations, and
other significant or useful locations into the unit when planning the
trip. That's also the best time to annotate your waypoints with
meaningful names. After that, selecting a destination with GoTo is
easy. Also, once your waypoints are programmed, it is fairly quick
and easy to create one or more routes.

In the 12XL you can program the absolute coordinates of a waypoint as
well as the relative coordinates. Naming a waypoint using the rocker
pad is tedious, but even two- or three-character abbreviations such as
A1, A2, etc., can be meaningful without being too tedious to enter.
For a trip to Sand Island in the Apostle Islands, I labeled the major
references on the island SAND1, SAND2, etc. going around the island in
a clockwise direction, but I could have used S1, S2, etc.

If you use the Mark button to record your location, the default name of
the waypoint is a sequential number, but if you can remember which
number you started with for a particular trip and where you marked the
waypoints, you still have some useful information. It is less confusing,
however, to name the waypoints yourself.

Also, if the waypoints are sequentially numbered, you can select a
destination by highlighting it on the Map page, where the relative
positions of the waypoints are shown, and pressing GoTo. You can select
the orientation of the Map page to have either north up or your
direction of travel up. With sequentially numbered numbers, north up
would probably be least confusing, since the Map page would be oriented
like a paper map.

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.

Chuck Holst  
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From: Geo. Bergeron <heritage_at_europa.com>
subject: Re: [Paddlewise] Garmin 12XL GPS unit: Navigation
Date: Tue, 23 Jun 1998 13:03:04 -0700
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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