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GPS was developed for
the military for field position, so each unit could know exactly where
they were
without any navigation aids, or training for that matter. The military
used your tax dollars to launch a series of
satellites all around the planet which emit timed signals continuously.
The GPS units receive this information
and calculate, (we all remember or Trigonometry now don't we), exactly
where you are based on the know
positions of the satellites. Enough theory, the result is you can know
very accurately just where in the world
you are, anytime, anyplace, any weather, any how. Sound Great? Look a
bit closer before you buy into all of
this.
Since your tax dollars
paid for this thing, Congress insisted you be able to use it. Now the
military wasn't
too thrilled about the idea, but compromised with the idea of a
"degraded" mode. What this mode does, is
scramble the very exacting information just enough where instead of
getting within 10 feet, like Uncle Sam,
John Q. Public could get within, say, 100 feet. Congress said OK but
only use the scrambler if you're off in
some conflict and it could be a matter of National Security. The
military quickly agreed and has proclaimed
that we be Nationally Secure continually since 1991. End result, don't
expect to get any closer than 100 feet
to where you want to go. Bear in mind I've spent all day very happily
exploring an area 200 feet square, or
4000 square feet. OK, so it won't get you exactly where you want to go,
but still, pretty close. Oh, and by the
way, that's 100 feet in any direction, and it changes every few seconds.
That means you can trust it to get
close, just don't count on it keeping you close.
Another little problem
you should be aware of, this thing was designed for the foot soldier.
You can't walk at
60 mph, so relative to a bass boat, this thing is slow. If you wait
until this thing says you're there, you're about
1/4 mile past it. This also means you're likely to get pretty confused
buzzing around on a plane within 1/2 mile
or so trying to steer where the unit says to go now. Even in the fastest
modes, the unit can take up to 30
seconds to figure out just were in world you are after you've stopped.
When you get close, it's idle time. You've
got to slow down to the unit's speed, because it won't speed up to
yours.
One little final
thing, GPS is based on what's called geodedic coordinates, not the
magnetic scale your
compass uses. For the purist, it's a difference of 7 degrees relative to
earth core at the equator. For those less
technically interested, it means if your unit says to go at 180 degrees,
and you head off due south by your
compass, you're going to miss the mark by a little bit. A detail, but
sometimes an important one.
So, these things have
soo many problems they're worthless, right? WRONG! You just have to
understand
how the unit works, take advantage of the things it does well and
compensate for the rest.
Using a GPS
Regardless
of the type of unit you have, (more on differences between units later),
they all will give you a
direction and distance to the place you want to go. Before we look at
just how to get there, let's take a look at
just where we're trying to get.
The most important
thing you'll ever do to make getting back to a place easy is the time
you first enter in
the destination in the unit. As we saw earlier, the GPS system has a
built in, (and active), degraded mode
which will introduce an error into our location under the best of
circumstances.
The first trick in
using a GPS is how to reduce the error before you enter it. The best way
is also the
longest and most time consuming. Throw out a buoy and use your trolling
motor the circle around it. Keep an
eye on the coordinates as you move. If you watch closely, you'll see a
pattern develop as the randomizer
works in time most noticeably in the N/S coordinate. If you watch you're
unit long enough, you'll see the
transition or reset of the mode which will appear as a jump, normally
North to South, of coordinates even
though you're standing still right beside the buoy. If you remember the
coordinate that's farthest off North, and
the one farthest off South, and take the average, you'll get just about
right. Same thing for East to West. How
long will this take? To really make sure you're within say 15 feet,
about an hour. Is it worth it? If you have any
other way of relocating your spot, no. Just allowing the unit to fully
settle, which takes about 5 minutes for full
filtering, will get you very close, say about 30 feet, or one cast. The
less time you wait, the farther you'll be off.
If you were moving fast, say coming by on a plane, you could be off by
several hundred feet, just because of
the time lag for the update rate. So, the end result is to spend a
couple of minutes for every important location
before entering it in the unit. This will pay big dividends later in
trying to return to the spot.
OK, now we have that
honey hole dialed in, and we're setting a few miles off. Just how do we
get from point
A to point B with our GPS? My personal preference is to use my compass.
I check the GPS from the
direction, then "steer to" with the compass to get me off in
the general direction. As I'm running, I'll adjust
course until my heading, as shown on the GPS, matches my destination,
also on my GPS. At this point, just
check the compass and fly in on instruments. You can certainly strike
out in the general direction and depend
on the GPS as your sole guide, but the update rate will lead you on a
zigzag path before you get there. This
all works great for general navigation, say running across the Big O and
hitting King's Bar within a few hundred
feet. But what about finding that honey hole?
When we get within
around 1/4 mile, it's time to set her down. From this point I idle into
the hole, letting my
GPS catch up with my position. My unit, like most, shows a speed over
ground, (SOG), and I'm confident in
the location as soon as that reads something I can believe, like about 4
MPH instead of 40. As the SOG
drops to range, I revert to one of my older methods to exactly locate my
hole. I either use a line up of a couple
of shore objects, if I'm in a position to see any, or I use my depth
finder. One of the beauties of the problem is
that if I'm not within shore sight, then I'm most likely on some type of
structure, a point, breakline, or
something. That's about the only reason I can think of to be looking for
an exact position. If I'm on some type
of schooling pattern or such, then the location isn't that important. If
I do need exact boat position, then the
traditional ways of locating the boat over the structure still work.
The moral of this
story is a GPS will not find anything for you that you can't somehow
find now, given most
cases of offshore and near shore fishing. What it can do is save you a
bunch of time by getting you close.
For long distance navigation, (what it was designed for), the thing
works like a dream. For short distance
navigation, it's helpful if you work within the limits of the unit and
have a fall back after you get near you
destination.
So, is that the whole
story? Not quite. One of the more remarkable things about computers,
(and that's all a
GPS is), is they don't forget things as fishermen are prone to do. The
GPS finds a spot based on coordinates,
not the 3 reeds that were set out from the reed line year before last.
So, while finding your normal spot on your
home lake may not require a GPS, finding that spot again you did so well
in the tournament 3 years ago,
might. The other thing is a GPS works the same no matter who owns or
manufactures it. This means, unlike
say a LORAN unit, two people can share GPS coordinates and find exactly
the same spot, with one never
having been there. This is a major asset if you happen to have a buddy
who's home lake you're going to fish
next month and also owns a GPS. There is even a small, but growing
business of selling GPS hot spot
coordinates on major lakes. A GPS may not help you find that spot the
first time, but it can sure help find it
the second time.
Going Shopping
So you've
decided to take the plunge and join the GPS revolution. What to look
for? Why is that unit better
than the other?
The first thing to
know about shopping for a GPS is the chip that does all the magic for
computing the
location, filtering, averaging, etc. is made, and patented by Raytheon.
That means that all GPS units compute
and process the GPS information exactly the same, regardless of price or
features. Don't buy into the fact that
one unit is more precise than another, it's not. It's all of the
optional features that separate the units.
The biggest difference
between the units is the viewing screen. Since a GPS is a graphics
device, the
screen can make a world of difference. The most inexpensive models have
very small screens and little extra
information can be displayed. The top-of-the-line units have large
screens and can display just about every
piece of navigation information known to man, which is to say, more than
you need to know. I selected my
unit, which is a mid-priced unit, because with my failing eyesight, I
could still see the screen even at night. If
you have good eyes and want basic information, the most inexpensive
units will do fine.
The biggest difference
in price may be the antenna. This is a confusing issue which costs big
bucks. All
units can see the satellites with an unobstructed view, that is to say,
from a bass boat. The only reason for a
separate antenna is if you want your unit to operate with something over
it's view, like from the cockpit of a
cruiser. The "handheld" units can receive every bit as good
and the permanent mounts with external antenna
for about $300 less. The extra money is for the amplifiers and receivers
to drive the weak signal from the
antenna to the unit. On the "handheld" units, the antenna is
built in, so it doesn't need all the extra circuits.
Both units "hear" the satellites roughly the same.
Now you can't get
external antenna confused with a "differential" antenna. A
differential receiver gets an
extra LORAN signal from a shore source and computes extra timing
information from the satellite signal. This
will make your navigation more precise, if you have the recommended 34
foot difference between the main
antenna and the differential antenna. Since I don't know of any 34 foot
bass boats, I can't see any advantage in
a unit that is "differential ready", (they all are since it's
built into the basic GPS chip). Again for the purist, you
can divide the wavelength and place the differential receiver at a
binary length point with reduced effectiveness.
My question is, "Why?"
You'll hear a lot
about "routes" and "waypoints". From our standpoint,
a waypoint is a location or spot, and
a route is a line between two or more spots. Unless you want to navigate
through all of the canals on the
Butler chain without touching your unit, routes are pretty worthless to
bass fishermen. On the other hand, the
more waypoints the better. The inexpensive units store about 100
waypoints, the upper end units up to 1,000.
You may find the 100 number a bit cramped after a year or two, but
anything much over 200 will keep you
happy for quite a while.
Speaking of waypoints,
they are stored in the unit in "static RAM". This lets the
waypoint be saved even
through a change in batteries. This is not to say it is permanent. Even
the static RAM needs a occasional
refresh usually provided by the same battery as in your watch, good for
about 5 years. So, unless you want to
start all over again every few years, it's a good idea to keep a
separate copy of your waypoints. The best way
is on a home computer. The designers of the GPS thought about that and
most mid to upper priced units have
an output which can be directed to a PC. By the time you buy the unit,
buy the PC adaptor, and buy the
software for the interface, writing them down by hand or just copying
them in to your PC doesn't sound too
bad. It's another standard option within the chip specification if you
want it. Don't get too excited by the
standard output most mid-priced and up units have. It's designed to
interface with an autopilot on a large
vessel so you won't find much use for it right now.
One big difference to
seriously consider is the naming of waypoints. Most units allow you to
enter the name
of a waypoint. Unless you're very good at remembering numbers, this is
something you will want to do. The
difference between units is the number of characters you can have in the
name. Lower priced units allow up to
say 6 characters, more than a bit cryptic for a couple of hundred
waypoints. The better units will allow 12, 16
even 32 characters for a name. It doesn't sound too important now but
just wait until you try to come up with a
name for the 6th point you found today on Lake Stickapig.
Most units allow you
enter the current location with the push of a single button. This is
almost mandatory if
you like to enter waypoints by just idling over them. Another way to do
the same thing is your MOB feature,
standing for Man Over Board. It's a nice feature with too many side
effects in most units, so don't spend extra
money for MOB. However you enter a waypoint, make sure your unit will
allow you to name and sort them.
Everyone wants to show
you their "steer to" screen, which is nothing more than an
artificial horizon view of
your course based on your destination. This is the screen everyone
starts out wanting to use, and ends up
pitching in favor for numeric position. The screen is a very nice
graphic interface if you're going very slow at a
long distance, (which case we said we'd prefer the compass since it
updates faster.) For normal and close in
navigation, the update rate for the filters is too slow to be of much
use. Most of the better units have this
screen, just don't pay a bunch extra for something you'll quickly out
grow.
The one
"feature" you won't leave home without is the mounting
bracket. These pieces of plastic convert
your handheld unit to a console mount. They provide for battery power,
(a must), and hold the unit on the
console, for the most part. One thing I've discovered is the mounts
weren't designed for bass boats going over
2 foot wakes. It's a good way to find you're unit in your lap, or worst,
over the side. To cure this, I added an
option, a very large rubber band from a cheap pair of goggles. It holds
my unit in place even in the roughest
waves. I may still loose electrical contact, but the unit is still
on the console. Mounting brackets are available
for just about all handheld units and come standard with the mid-price
ones.
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