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RE: Want to know about GPS stuff!!

> I've been thinking about getting a GPS unit, to reduce
> the amount of time map reading. I think I understand GPS won't show
> you were your at on a map, but if you have a signal, and it's
> programed right, it will lead you to were you want to go, no matter
> how many detours or backtracks one must do.
> 1.Like which unit is prefered, Garmin or Magellan? (That's my price
> range, about $200.)

Following the concensus of friends and postings on newsgroup
sci.geo.sattelite.nav I got a Garmin model 45 ($300) and am extremely happy
with it.  I chose it over model 38 ($200) because I wanted a
remotely-mountable antenna for vehicle use.  An external antenna may be a
liability for handheld use in the woods because it could get broken off.
Garmins are apparently less battery-hungry than competitors.  The ones made
for boating are weatherproof.

> 2. Is it worth buying a GPS for hiking?

Purists would say no.  If it increases your enjoyment, go for it!  (I love
navigation; it's been a hobby since I encountered topo maps at age 10.)  As
with instrument flying, one should not rely upon a single system (current
events in Bosnia notwithstanding).  Map and compass are of course adequate
but GPS offers unique capabilities.  With GPS and a two-way radio you can
in theory call down a medical helicopter to carry away sick or injured
people.  (Quartz crystals actually do have healing powers :-)
With GPS you can be a Technobuddhist:  If you encounter spiritual
enlightenment, you can erect an environmnetally-correct virtual shrine
simply by pushing a button to record the location.   Ohmmm...  :-)

> 3. What's best place to buy...

Mine came from West Marine.  See also Wal Mart.

> 4. What's the best way for a hiker to program waypoints, ie,
> Latitude & Long, UTM, etc?

UTM is easiest to measure from topo maps:  Units are decimal and scale is
constant ("grid north" is neither true nor magnetic, but close enough).
I'm used to lat/lon; I use aeronautical sectional charts for roadmaps,
especially "out west." BTW, new sectional charts cost about $7 but they
become obsolete for air navigation every 6 months, so used ones can be
found inexpensively or free.

> 5.What map computer program is most useful to get waypoints from,
> to preprogram the GPS?
> 6.Are there anymore specfic GPS 'puter programs...

GPS web site:  http://www.tech.net/technotes/gps
The FAQ on Garmin products includes software reviews.

> 7.What are the best distances apart to use for waypoints, for
> hiking? (5, 10, 30, etc?)

Use personal preference.  Perhaps set significant destinations, or just
turn the unit on occasionally to check progress and record present position
each time.  On a well-marked north-south trail, latitude alone is sufficient
for a fix.

> 8.What measured unit, statue, nautical miles, or kilometers, is
> best to use? ...

I use statute miles because they're most familiar.  Meters are appropriate
when using UTM coordinates.  Nautical miles are good for lat/lon navigation
by sea or air where there are no landmarks:  A nautical mile is one
arc-minute of latitude, 6076 feet.  It is very nearly 2000 yards or 2

GPS altitude is nearly worthless due to "selective availability" error
(which may be removed someday if the vote-getting potential of promising to
remove it wears thin.)  GPS altitude is not referenced to sea level, but to
the the center of mass of the earth around which the satellites orbit.  The
earth is not perfectly spherical and has gravitational anomalies; maps are
available showing variation between sea level and GPS zero altitude (about
40m max in continental US).

A rule of thumb for estimating walking speed:  The number of paces walked
in 36 seconds, divided by 10, is your speed in miles per hour.  A pace is
one full cycle of the legs, i.e., two steps.  The original definition of a
mile was 1000 paces as marched by the Roman Army; he word comes from Latin
"mille," meaning 1000.  One pace is 1/1000 mile, 36 seconds is 1/100 hour.
Calculate the appropriate time period if your pace is significantly
different from 5.28 feet.  It doesn't work on rough terrain.

--  Frank     reid@indiana.edu