(written in 1997)
by: Paul Crawford
(reprinted with permission from author)
(some up to date information inserted in article since written)
The Global Position System, (GPS), has come to the
angler. This military marvel has come down in price where even the bass
fisherman can now afford one. The question seems to be, "Why do I want
one?" The answer is, "Maybe you don't." Let's take a look at what one
of these things can, and can't do, and how to use one if you shell out
the bucks.
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 scrabble 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.
(INSERTED UPDATE! SINCE
THIS ARTICLE WAS WRITTEN, DEGRADING OF THE GPS HAS BEEN TERMINATED AND
IS NO LONGER IN AFFECTING GPS SIGNALS! THEREFORE YOU NOW GET A TRUE POSITION
WITH GPS!)
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
geodetic 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 soooo 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
plan e, 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, break line, 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 allot about "routes" and "way points".
From our standpoint, a way point 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 way points
the better. The inexpensive units store about 100 way points, 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 way points, they are stored in the unit
in "static RAM". This lets the way point 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 way points.
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 adapter, 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 way points. Most units allow you to enter the name of a way point.
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 way points. 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 way points 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 way point, 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.
There are, of course, all sorts of other things,
which are all just bells and whistles, all of which add to the cost of
the unit. Expect to pay about $300 for the lowest cost units.
(INSERTED UPDATE! NOW SOME GPS UNITS ARE PRICED
AROUND $100.00!)
Some units can cost up to $2,000. Even if you prefer the better screen,
more way points, longer names, and the like, you can find a very good unit
for $500 - $700. These mid price units normally come with the mounting
bracket and 12V adapter, which is a $60 - $70 item on the less expensive
units, so they're not that much more expensive. Choose the unit with the
features important to you at the cost you are willing to pay.
The GPS units aren't magic, and they're not
for everyone. If you are a serious tournament angler that likes to fish
deep structure off shore, then it's a tool you need to consider. For those
who are going to make the run across the Big-O on a regular basis, it's
a piece of safety gear highly recommended. What ever your needs, GPS units
are here to stay and are one more tool the angler needs to be aware of,
if only to say, "I'll wait until the price comes down."