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Mike Busch |
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 NOTE: Since this comparison was originally written, Garmin introduced its
lower-priced GPS III Pilot which also has ground-mapping capability. We've reviewed this
unit in a separate article. Lowrance subsequently introduced
its own lower-priced unit, the AirMap 100, which we've also reviewed
separately. |
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- Lowrance introduces smaller AirMap 100 priced at $599, which we've reviewed in a separate article. (20-Apr-98)
- Lowrance introduces 12-channel AirMap 300 priced at $799, and discontinues the original
5-channel AirMap. (19-Jan-98)
- Garmin introduces another ground-mapping unit, the GPS III Pilot, which we've reviewed
in a separate article. (01-Sep-97)
- Lowrance drops the price of the AirMap and AirMap SE by $200. (15-Jun-97)
- Lowrance AirMap software update v2.1 adds obstruction mapping, and the availability of
an optional rechargable NiMH battery pack. (14-Apr-97)
- II Morrow Precedus software update v6.1 adds new HSI screen, enhanced pan/zoom
capabilities, and coastlines and political/territorial boundaries to the map display.
(18-Nov-96)
- Lowrance AirMap free software update v1.9 adds SUA look-ahead, VNAV, reduced keystrokes.
(07-Oct-96)
- Garmin says GPSMAP-195 order backlog remains at 6-to-8 weeks. (07-Oct-96)
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Ground Mapping ... What's the Big Deal?
I must admit that when I first set eyes on the Lowrance AirMap in May, I
was enormously skeptical about the merits of ground mapping in an aviation GPS handheld.
Keep in mind that my flying is about 99% IFR, and that I'm not in the habit of paying
attention to roads, rivers or railroad tracks, much less using them for navigation.
I'd flown with virtually every handheld GPS available up to that point, particularly
the Garmin GPS-90 and the II Morrow Precedus, and also flown behind the Argus 5000 and
7000 panel-mount moving maps. It seemed to me that moving map displays were already too
cluttered with airports, navaids and special-use airspace boundaries, especially in the
complex and densely-packed airspace around Los Angeles and San Francisco where I often
fly. So my first reaction was that I needed highways, waterways and other terrestrial
features on my moving map about as badly as I needed a third control yoke or a quadricycle
landing gear.
But my first long IFR cross-country trip with the Lowrance
AirMap changed my opinion. I found that the AirMap's display was not excessively cluttered
or hard to read, despite the presence of ground mapping features. The AirMap's
high-resolution display (with its 25,600 pixels capable of not only black and white but
also gray) and its clever de-cluttering software (which automatically drops less-important
map features as you zoom out to longer-range views) kept the display easy to interpret.
And the ground features, although certainly not necessary for IFR X-C navigation, made the
flight much more enjoyable:
"Ladies and gentlemen, we've just passed over the Sunshine VOR. To the left of
the aircraft, you can see beautiful Lake of the Ozarks, one of Missouri's major
recreational areas. The highway to our right is Interstate 44 which runs from Tulsa to St.
Louis. The airport just on the other side of I-44 is Forney AAF which serves Ft. Leonard
Wood..."
So while I still consider ground mapping to be a luxury rather than a necessity, I
found it to be a very seductive luxury. The next time I flew with a moving map that lacked
ground mapping, it somehow seemed to be crude and archaic. Luxuries are often like that:
hard to give up once you get used to them.
Now there are three
Lowrance introduced the AirMap with an unprecedented advertising campaign in March
1996, showed the unit at Sun 'n Fun in April, and started production-quantity deliveries
of customer units in May. Since then, they've been selling AirMaps as fast as they can
make them.
Garmin showed an early prototype of their ground-mapping handheld
— dubbed the GPSMAP-195 — at Sun 'n Fun '96, but it became clear that Garmin's product
development cycle was months behind Lowrance's and that they'd be lucky to have the 195 in
production by Oshkosh in early August 1996. As it turned out, Garmin did deliver their
first batch of production 195s to their dealers at Oshkosh. But it was a very small batch
(about 100 units, we estimate) and sold out immediately, so most would-be buyers went home
from Oshkosh empty-handed.
Not wanting to be left out, II Morrow released in late
July 1996 an upgraded version of their Precedus handheld with mapping of highways and
cities. The upgraded Precedus was in plentiful supply at Oshkosh. The ground-mapping
upgrade required doubling the size of the unit's flash memory from 2 to 4 megabytes, but
II Morrow offered a hardware retrofit for owners of earlier Precedus units, and in fact
was performing the retrofit at their booth at Oshkosh on a while-you-wait basis!
Like thousands of other pilots, I checked out the new Garmin and the upgraded Precedus
at Oshkosh '96. But there's no way of evaluating complex products like these in a quick
in-booth demo. You've got to take them flying, preferably on a cross-country trip of
significant length, to do a really meaningful review. I knew that my flight from Oshkosh
back to California would be a perfect opportunity to put these units through their paces.
So in the waning "dog days" of Oshkosh, with the crowds gone and the exhibitors
impatiently waiting for the end of the show, I decided to see whether I could get my hands
on all three competitors and conduct a real fly-off during my trip home.
I already had a loaner AirMap, and the nice folks at the Lowrance booth updated it to
the latest software version (1.8 at that time). Tom Rogers of Avionics West had some of
the upgraded Preceduses in stock and arranged for me to borrow one for the trip. The
Garmin was the most difficult to come by because they were in such short supply and all
customer units had long-since sold out. But Bob Cusick of Garmin came to my rescue by
loaning me his personal demonstrator GPSMAP-195 for the flight home, after I solemnly
promised him that I would FedEx it back to him the moment I got home. (Bob made me prick
my finger and sign my name in blood.)
So Thursday morning, I launched westbound from Oshkosh in
my Cessna T310R with three ground-mapping GPS handhelds aboard: an AirMap, a GPSMAP-195,
and a Precedus. The flight to Santa Maria, California, was nearly 1,700 nautical miles,
with a fuel stop at North Platte, Nebraska, and an R.O.N. at Grand Junction, Colorado. The
route took me across the Great Plains, through the Denver Class B airspace, over the
Rockies, through the maze of MOAs and Restricted Areas near Tonopah, Nevada (can you say
"Area 51"?), across the 14,000-foot peaks of the Sierra Nevada, and across
California's San Joachim valley to the Pacific coast. The entire trip was made under
Instrument Flight Rules. Cruising altitude was 12,000 feet from Oshkosh to Denver, and
FL180 (with a cannula up my nose) for most of the remainder of the trip. The weather was
mostly clear and unrestricted, except for an area of airmass thunderstorms between Denver
and Grand Junction that necessitated a good deal of off-airway deviation.
It was a marvelous flight, and a terrific opportunity to wring out the three GPS
handhelds. Here's what I learned.
Hardware Comparison
Size and appearance
When you place the three handhelds side-by-side, the first thing you notice is a big
difference in size. All three are about the same height: 7-1/2 inches, give or take an
eighth. But the Precedus is much slimmer and more svelte than the other two. It looks
rather like a cellular telephone with an oversized display, and in fact is only slightly
bigger than my Mitsubishi Diamond-Tel cellphone or my ICOM IC-A22 comm transceiver. Like a
cellphone, the Precedus fits comfortably in one hand and is easy to operate one-handed if
you operate the keyboard with your thumb.
The AirMap and Garmin 195 are both half-again as wide as the Precedus (roughly 3 inches
versus 2-1/8 inches). Both are uncomfortably large for one-handed operation; you find
yourself either holding the radio in one hand and punching the keys with the index finger
of the other hand, or else cradling the radio in both hands and operating the keys with
both thumbs.
The Precedus and the AirMap are about the same thickness: 1-3/8 inches. The Garmin is
substantially thicker at 2-1/8 inches, partly due to its unusual "sculptured"
shape. It's big. About the size of a brick. A lot bigger than it looks in the advertising
photos. Any bigger and you really couldn't call it a handheld. In fact, when I used the
units in my motel room (for familiarization, pre-entering routes, and so forth), I almost
always found myself placing the GPSMAP-195 on a desktop or tabletop and using it that way.
Appearance-wise, both the Precedus and the Garmin 195 project the look and feel of
quality. The Precedus is packaged in a cast aluminum enclosure which gives it a solid feel
and a surprisingly heavy weight considering its slim proportions. The Garmin's case is
plastic, but its deeply sculptured shape and rubber inserts gives it a quality look.
Surprisingly, the Garmin is only slightly heavier than the Precedus (1.4 lbs. versus 1.2
lbs.) despite its far bigger size.
By comparison, the AirMap plastic case gives it a somewhat cheaper-looking appearance.
Of course, the AirMap is a good deal cheaper: $699 street price, versus about $995
for the Precedus and $1,199 for the GPSMAP-195. In actuality, however, the AirMap seems to
be at least as rugged and well-built as the other two models. In fact, the AirMap's
unusual flip-top antenna (which covers the display when folded to the closed position)
means that you can toss the AirMap into your flight bag or briefcase without having to
worry about scratching the display; with the Precedus or the Garmin 195, you have to slide
the radio into its protective carrying case to keep the display from getting damaged.
Incidentally, the plastic case of the AirMap is welded shut, and can't be opened
without destroying it. The Garmin's plastic case is screwed together with a gasket and
nitrogen-filled. The aluminum case of the Precedus opens easily by removing a few screws,
which made it possible for II Morrow to retrofit older units with the larger flash memory
required for the mapping upgrade.
Display
Perhaps the most significant hardware differences among the three units relate to their
LCD displays. The Precedus, which was designed without ground mapping in mind, has a tall
rectangular 1-3/8 by 2-7/8 inch display with 12,800-pixel resolution (80 by 160). With its
intense blue color and large .45-millimeter pixel size, the Precedus display has the best
contrast and readability of the three units over a wide range of lighting conditions and
viewing angles, particularly in direct sunlight. But its lack of gray-scale capability
severely limits its ability to portray ground mapping information in a legible fashion.
The Lowrance AirMap has a square 2-1/4 by 2-1/4 inch display. Its resolution is twice
that of the Precedus: 25,600 pixels (160 by 160). Each .35-millimeter pixel has 3-level
gray scale capability (black, white, or gray). This greatly enhances its ground mapping
capability, since mapping features like lakes, rivers and ATC rings can be shown in gray
without obscuring the airport and navaid icons and labels that are shown in black.
The importance of the AirMap's gray-scale display is particularly obvious when
operating the AirMap in split-screen mode where the left half of the screen displays a
moving map and the right half displays alphanumeric flight data. In this mode, the
AirMap's map is 80 by 160 pixels — precisely the same resolution as the Precedus and 22%
smaller. Yet if a significant number of ground mapping features are visible, the AirMap's
half-screen map is far more legible than the Precedus's full-screen map. Gray scale is the
difference.
The Garmin GPSMAP-195 display goes even further. It has exactly the same width and
pixel size as the AirMap, but is half again as tall: 2-1/4 by 3-3/8 inches and 38,400
pixels (160 by 240). Perhaps even more important, the Garmin's display supports 4-level
gray scale (black, dark gray, light gray, white), giving the GPSMAP-195 an even better
ability to display dense ground mapping information while still remaining legible.
The downside of these gray-scale displays is impaired contrast and a narrower viewing
angle. I found both the AirMap and the Garmin 195 displays difficult to read clearly in
direct sunlight. Usually, an adjustment to the display's contrast setting solved the
problem, but when the lighting conditions changed, the contrast needed to be adjusted
again. Although the blue-and-white display on the Precedus also has adjustable contrast, I
never needed to fiddle with it.
All three units have backlit displays for night use. The Precedus and Garmin 195 both
have white backlighting with three intensity levels (high, medium, low). The AirMap uses
green backlighting with 16 intensity levels. All three are a real pleasure to use at
night, particularly when operating off aircraft power so that the backlight can remain on
continuously. When operating off battery power, all models extinguish their backlight
after a time-out to maximize battery life.
Keypad
The differences in keypad design of the three models are not as obvious at first glance
as the differences in their displays. But the importance of keypad layout and position
becomes clear after you've flown with the units for awhile, particularly at night and in
turbulence.
The Precedus uses a simple 3-by-3 keypad layout, with nine large
oval fingertip-sized keys located at the extreme bottom of the faceplate. Its large keys
are wonderful for one-handed operation (when your thumb is the only finger available), and
for use in turbulence. At night, they keys are magnificently backlit, appearing as glowing
ovals with white legends. But nine keys don't seem to be quite enough. I wish II Morrow
had added one more row of keys, like a telephone keypad. The absence of dedicated
zoom-out/zoom-in keys and a "cancel" key are particularly noticeable.
The Garmin 195 has plenty of keys — eight small chicklet-style
function keys, plus a two-way zoom-in/zoom-out rocker key and a four-way
left-right-up-down cursor control rocker — essentially 14 separate keys. The keys are
logically labeled and consistently employed, providing a straightforward user interface.
The keys are black with white legends, and the legends are backlighted for night use.
But I found the Garmin's four-way cursor control keys to be more difficult to use than
the four separate arrow keys used by the Precedus and AirMap. And sometimes I would have
to press a key two or three times before the Garmin would recognize my keypad input; I
couldn't tell whether this was a hardware or software problem, but I suspect the latter
(so it's probably fixable).
(One possible explanation: if the Garmin's backlighting is activated — intentionally
or otherwise — and times out, the first keypress of any key turns the backlighting on and
doesn't perform its normal function.)
My biggest complaint about the Garmin keypad is its placement at the top of the unit,
rather than at the bottom. The top-mounted keypad is fine when you're holding the 195 in
both hands and operating the keys with your thumbs. But when the radio is in its yoke
mount (where it is most of the time) and you're punching the keys with your index finger,
it's hard to avoid covering up the display with your hand. Worse, the Garmin's top-mounted
keypad dictated a bottom-mounted display, which I found to be too low for comfortable
viewing during yoke-mounted operation. I often found myself having to tilt up the yoke
mount to get a better view of the screen, which unfortunately causes the radio to obscure
the instrument panel.
The AirMap 300 keypad splits the difference between the Precedus and
the Garmin. It has twelve keys, and is placed right in the middle of the unit, below the
display and above the battery pack. This placement works well for both handheld and
yoke-mounted operation. The keys are black with white legends, and at night the backlight
makes them glow a luminous green. I only wish the keys were a bit larger — there seems to
be plenty of room in the AirMap's keypad layout for big, Precedus-sized keys.
Battery
Like the cellular phone that it resembles, the Precedus comes with a quick-change
rechargeable ni-cad battery pack and a wall-transformer-type charger. In fact, the battery
pack used by the Precedus is a standard NEC cellphone battery, so replacement battery
packs are readily available anyplace that carries NEC phones. The standard battery is good
for about 4 hours, but high-capacity packs offering 6 hours to a charge are also
available.
The Garmin 195 comes with a battery case designed to hold six AA-size alkaline
batteries, which Garmin claims will last "up to 10 hours" if backlighting is not
used, although that figure seems a bit optimistic based on my tests. Garmin also offers an
optional rechargeable ni-cad battery pack with an AC charger, which they claim will last
up to 9 hours to a charge. But there is no provision for charging the pack in-flight while
the GPS is being powered from the aircraft electrical system...a serious shortcoming in my
view. In the event of an in-flight electrical failure, the Garmin's battery might easily
start out with less than a full charge. Consequently, the ni-cad option on the Garmin 195
might not be such a good idea unless you also carry an alkaline battery pack loaded with
six fresh AA's as a backup.
The AirMap 300 has the most flexible power system of all. It comes standard with two
battery packs: an alkaline pack that takes six AA-size batteries, and a rechargeable NiMH
(nickel metal hydride) pack with a built-in smart charger. The NiMH battery is immune from
the "memory effect" that plagues ni-cads, can be recharged in-flight while the
GPS is in use, assuring that it'll be fully charged in the event of an electrical failure.
(An AC charger is not included, but is available for an extra $30.) Battery life varies
from 4 to 10 hours, depending on what update rate is configured. The AirMap can also be
run off aircraft power with the battery pack removed, reducing the size of the unit by
nearly half and making it extremely compact.
Opinions are divided concerning whether alkalines or rechargeables (ni-cad or NiMH) are
the better power source for a handheld GPS. Many pilots prefer alkalines because they have
excellent shelf-life, provide about twice the running time of ni-cads, and are available
at any drugstore or supermarket. I prefer rechargeables because I normally fly with the
GPS plugged into aircraft power, so battery operation is only an issue for me during
ground use or in the event of an in-flight electrical failure — and in either case, 4
hours is plenty. Good quality AA alkalines (I prefer Duracells) cost a dollar or more
apiece, so a new set of alkalines for the AirMap or Garmin 195 costs at least six bucks.
Antenna
All three models use a flat patch-style GPS antenna. The Precedus and Garmin 195 use an
antenna mounted in the "nose" of the radio, while the AirMap uses a unique
"flip-top" antenna hinged to the top of the unit and serving also as a
protective cover for the display when the AirMap is not in use.
For in-flight use (at least in my airplane), it proved essential to use a
remote-mounted antenna located on the glareshield or suction-cup-mounted to the
windshield. All three models allow for this, but in different ways. Both the Precedus and
the AirMap allow their attached antennas to be removed from the radio and mounted in a
suitable location, and both include a coaxial cable for hooking the remote-mounted antenna
to the radio. The antenna on the Precedus slides off and back on very easily. The flip-top
AirMap antenna used to be rather a pain to detach and reattach, but Lowrance redesigned
the antenna attachment scheme in the spring of 1997, and owners of earlier models can
retrofit their thumbwheel-type units easily. The Garmin 195 offers the best solution
of all: a separate remote antenna and cable that can be left permanently in the airplane
(assuming you own one), and plugs into an antenna jack on the radio. All three models come
with a suction-cup mount for remote-mounting the antenna to the windshield.
Yoke Mount
Yoke mounts also come standard with all three models. I like the one that comes with
the Precedus best by far: it's small, sleek and elegant (like the radio itself) and
something you don't mind leaving in the airplane permanently (again, assuming you own
one). The Precedus snaps in and out of its yoke mount easily.
The Garmin yoke mount is much bigger, heavier, and more complex (as is the radio). A
knob on the mount is used to lock and release the radio. The cigarette lighter power cord
screws onto a couple of little ears on the yoke mount and automatically engages the power
connector on the 195 when it is locked into the mount. I found, however, that the power
connector doesn't make reliable contact unless you're very careful about how you insert
the radio into the yoke mount. This isn't a big problem once you're aware of it, but it
definitely can bite the novice user. The Garmin does display an icon at the bottom of the
screen to show which power source is being used, and it's a good habit to double-check it.
The AirMap yoke mount is my least favorite of the three. Not only is it big and heavy,
but it relies on Velcro rather than clips to attach the AirMap to the mount. I found that
the Velcro simply isn't strong enough (or perhaps not enough of it is used) to hold the
AirMap securely to the mount, assuming you fly with one of the battery packs in place.
It's not hard to dislodge the radio inadvertently, and I'm concerned that a yoke-mounted
AirMap might become a projectile in severe turbulence (although it did hang on okay when I
flew through some moderate bumps). With the battery detached and running solely on
aircraft power, the AirMap becomes small and light enough that the Velcro mount is fine.
Software and database updates
All three models are designed so that both their databases and operating software can
be updated in the field. The Precedus and Garmin 195 are both updated by hooking the radio
to an IBM-compatible PC using a special data cable and uploading the update from the PC.
The updates are distributed on copy-protected diskettes. Although this approach works
fine, we have two beefs with it. First, both II Morrow and Garmin classify the data cable
and PC update kit as extra-cost options ($100 for the Precedus, unknown for the Garmin);
we think they should be included as standard equipment. Second, unless you have an
IBM-compatible PC, you're out of luck. (Macintosh owners might get away with using a PC
emulator like Soft-PC, but I haven't been able to confirm this.)
The AirMap uses a totally different scheme, one that I like a lot better. Database and
software updates are distributed on tiny cartridges that plug into the back of the radio.
When a new database update arrives, you simply pull out the old cartridge, plug in the new
one, and send the old one back to Lowrance in the special mailer that comes with the
update. Software updates are slightly different: you plug the software cartridge into the
AirMap and turn it on, whereupon it automatically loads the new software into its internal
flash memory; then you unplug the software cartridge and mail it back to Lowrance. No PC
or cable is required. Furthermore, Lowrance charges substantially less for its Jeppesen
database updates than the competition ($75 for the AirMap versus $125 for the Garmin).
Software Comparison
All three models are loaded with features, most of which are implemented in software.
And all three allow their software to be updated by the user. II Morrow introduced the
Precedus at Oshkosh '95, and has been continuously refining and enhancing its software
since then, and owners of even the earliest Precedus units have been able to benefit from
the improvements. Lowrance and Garmin have both released a number of improved software
refinements, and the enhancements are likely to continue.
Menus
All three units use menu-driven user interfaces, but there are significant differences.
The Precedus has a single 13-entry function menu that appears whenever the user presses
the "menu" key. You select a menu function by moving the cursor to the desired
item with the up/down arrow keys, then pressing the "enter" key. The top menu
item is "Return to Nav" which takes you back to the navigation/map pages. The
other 12 menu items call up specialized pages that permit you to configure the various
system and mapping functions, initialize the GPS position and clock, start and stop
timers, perform E6B functions, access checklists, and so forth. For the most part, the
Precedus user interface is very straightforward and easy to learn and use.
The AirMap also uses a single function menu that appears when the user presses the
"menu" key. The menu contains about 16 entries (sometimes one or two more or
less, depending on what feature are active) but only 6 of them are visible in the menu
window at a time — the rest much be reached by scrolling as you move the cursor through
the menu using the up/down arrow keys. I found the inability to see the entire menu at
once makes the AirMap a bit more difficult to learn and use, although it's not a major
obstacle. Another AirMap oddity: to execute a menu item, you hit the right-arrow key
(rather than the "enter" key as on other models). This feels strange at first,
but I got used to it quickly.
The Garmin's menu system works a little differently. Pressing the "menu" key
brings up one of several alternative menus, depending on what nav page is being displayed
when you press the key. If you press "menu" while looking at the map page, for
example, a map-option menu pops up; if you do the same thing while looking at the active
route page, a route-option menu pops up instead; and so forth. Regardless of which menu
pops up, pressing "menu" a second time brings up the main menu. I found this
"context-sensitive" menu approach to be harder to get used to at first, but it
saves a few keystrokes in the hands of an experienced Garmin user.
Because the Garmin has so many specialized menus, the menus tend to have relatively few
items, and they are displayed in a larger, easier-to-read font than the Precedus or
AirMap. Menu items that are inapplicable in the present context are "grayed
out", similar to Windows or Macintosh menus — a nice touch.
Navigation Pages
As it comes pre-set from the factory, the Precedus displays seven navigation pages:
- A full-screen map page
- A split-screen page with a 2/3-screen map plus four alphanumeric nav-info fields
- Two alphanumeric nav pages, each with up to twelve nav-info field
- A messages page
- A GPS status page
- A route page
The Precedus nav pages are highly user-customizable. You can specify between one and
four alphanumeric nav pages, each containing up to twelve fields that you can select from
a palette of 34 different nav-info items. You can also customize the four fields on the
split-screen page in the same fashion.
When the Precedus is in navigation mode (as it is most of the time), you cycle through
these various nav pages by pressing the up- and down-arrow keys. The left- and right-arrow
keys are used to zoom the map pages in and out. In flight, I find myself toggling
frequently back and forth between the split-screen map page (which I've configured to show
distance-to-waypoint, groundspeed, bearing and track) and one of the alphanumeric nav
pages (to see CDI, time-to-station and time-to-destination, among other items). This isn't
particularly difficult to do, but I've often wished for more than four nav-info fields on
the Precedus split-screen page. (II Morrow's software whizzes could have accomplished this
easily, simply by using a smaller font for the nav-info. But then I'm sure they'd have
gotten hate mail from hundreds of farsighted pilots who need the big, easy-to-read fonts!)
The Garmin GPSMAP-195 uses a very similar design as the Precedus, with a few important
differences. It has only one map page and one alphanumeric nav-info page, but that's
enough because its screen is so big that it can get three times as much information on a
page as the Precedus can. The Garmin does offer an interesting "HSI" page that
has no parallel on the Precedus. This makes a total of six nav pages in all, which you can
cycle through by pressing the "page" key. (The "quit" key cycles
through them backwards.) Map zooming is accomplished with the dedicated zoom-in/zoom-out
rocker key. This leaves the four-way cursor control rocker free for slewing the cursor
around the map (discussed below).
Like the Precedus, the Garmin allows user customization of all the nav-info fields from
a lengthy palette of choices. It also allows its single map page to be customized: you can
select a full-screen map or a variety of split-screen options with 2, 4, 6 or 8 nav-info
fields, or with 0, 2, 4 or 6 fields plus a CDI display. I settled on a split-screen
configuration with 6 nav-info fields plus a CDI display. That proved sufficient to display
almost all of the nav-data I needed to fly with, and still left enough screen space for a
very respectable (AirMap-sized) moving map. With this configuration, I found that I almost
never needed to toggle to another nav page except when using some exotic feature such as
VNAV.
The AirMap works a bit differently. It offers a tremendous variety of different nav
page layouts — 21 different pages if I counted correctly — most of them
user-customizable. In addition to the usual map, alphanumeric, and split-screen pages, the
AirMap offers a variety of dual-map screen layouts, where each map is individually
configurable and zoomable. Just to cite one example: you can bring up a display where the
left half of the screen is an ordinary moving map, the upper-right-hand quadrant is a
second map zoomed in tightly on the destination airport, and the lower-right-hand quadrant
displays four nav-data items (e.g., distance, groundspeed, bearing and track).
There are two downsides to the AirMap's plethora of pages. First, there are too many of
them to simply cycle through sequentially like the Precedus and Garmin do. To change nav
pages on the AirMap, you press the "mode" key to bring up a menu of pages, then
use the arrow keys to specify the page you want, and finally press the "exit"
key to make the menu go away. Definitely more cumbersome than simply cycling through six
or seven pages with a single key. Second, customizing the pages on the AirMap is more
difficult and less intuitive than on the other two units.
Ground Mapping
As I said at the outset of this article, I consider ground mapping to be a nice feature
of a handheld GPS, not an essential one. I certainly wouldn't choose which one to buy
strictly on the basis of its ground mapping capability alone. But if ground mapping is
your top priority, then the Garmin 195 has to be your GPS of choice.
Taking full advantage of its big, 4-level gray scale display, the Garmin software
engineers have managed to create a moving map that looks astonishingly like a sectional
chart. Highways, rivers and lakes look very much like they would on a chart. Railroad
tracks are distinguishable from roads by their little tick marks. Major metropolitan areas
are shown in light gray and labeled; smaller cities and towns appear in close-up zooms.
Airports appear as dark circles with a white slash through them, and the slash is even
oriented in the direction of the longest runway. VORs are depicted using the familiar
hexagonal VOR symbol (sans compass rose), and even indicate whether the navaid has
DME or not. The attention to detail is remarkable.
My hat is off to Garmin for doing such a first-class job with the mapping software.
About the only way they could make the GPSMAP-195 display look more like a sectional would
be to install a color display. Maybe that'll be the big news at Oshkosh '97...
The AirMap pioneered ground mapping in aviation handhelds, and does a very credible
job. The AirMap's display, while only 2/3 the size of the Garmin's, is still plenty big
and capable for the task. But the AirMap's marine heritage is obvious. Its standard
background map depicts rivers, lakes and coastlines in faithful detail, but highways are
sometimes mislocated by as much as a mile, and railroad tracks don't appear at all.
Airports and navaids appear precisely where they belong, but no attempt is made to depict
them using standard aviation symbology. In short, I found the AirMap's ground mapping
capability to be quite good, but the Garmin's to be breathtaking.
However, starting with the version 2.1 update, the Lowrance has added a unique new
capability to the AirMap: an obstacle database, and mapping of obstacles. Antenna towers
and the like now show up on the map, complete with their elevations (you can specify MSL
or AGL). This is a very useful safety feature, and one that the competition is sure to
notice.
The Precedus comes in a very distant third in the ground mapping department. Its
relatively small, non-gray-scale display was never designed for such a task. It's simply
impossible to depict very much ground mapping information on a display like that without
it becoming too cluttered to read. The Precedus ground mapping capability is limited to
highways and city names — no rivers, or lakes are depicted, nor railroad tracks. In the
version 6.1 software upgrade, the Precedus added coastlines and territorial/political
boundaries to the map.
This is not to say that II Morrow's highway mapping upgrade to the Precedus isn't a
worthwhile one. It's a nice addition, and it's a real tribute to II Morrow that they could
(and did) make such an upgrade available to all existing Precedus owners. But limitations
of the Precedus display hardware make it impossible for this unit to compete with units
like the AirMap and Garmin 195 that were designed from the outset for ground mapping.
All three models let you specify whether you want the map display to be oriented
north-up, track-up, or course-up. On the AirMap's dual-map pages, you can set the
orientations of the two maps independently. I normally use track-up orientation in-flight,
as I imagine most pilots do.
In track-up or course-up mode, both the AirMap and the Garmin include a "north
indicator" to give you a general idea of which way the map is oriented. (The Precedus
doesn't.) Both the Precedus and the Garmin display the little airplane symbol that
represents your present position about 3/4 of the way down the screen, so the map view
focuses on where you're going rather than where you've been. The AirMap puts the airplane
symbol in the center of the screen (again reflecting the marine heritage of the design),
but Lowrance told me they're changing this in an upcoming software update.
Zoom and Auto-Zoom
The AirMap and Garmin 195 allow you to zoom the map in or out over an enormous range of
scales. The AirMap zoom goes from screen widths of 0.1 NM to 4,000 NM, and the Garmin goes
from 0.1 NM to 3,000 NM. The maximum zoom-out lets you see the entire North American
continent at once — the maximum zoom-in would let you taxi to the correct tiedown in
zero-zero conditions (if it weren't for the DOD's Selective Availability program that
intentionally degrades GPS accuracy). Both units have dedicated zoom-in/zoom-out keys on
the keypad to control this function.
The Precedus zoom goes from 0.1 NM to 250 NM. The lack of extreme zoom-out is
inconsequential for in-flight use (where ranges of 5 to 150 NM are typically used). But it
is occasionally useful during flight planning on the ground; e.g., to answer questions
like "does my route from Cincinnati to Tulsa pass through Arkansas?" Not a big
issue. The Precedus doesn't have dedicated zoom keys, and uses the left- and right-arrow
keys instead.
When you zoom in or out on any of these models, there's a delay while the
microprocessor constructs the new map. And because I tend to zoom in and out a lot in
flight, I consider the length of this delay to be a significant issue. And in this area,
the AirMap wins hands-down. The AirMap almost never takes more than one second to display
the new map after a zoom-in or zoom-out request, while both the Garmin and the Precedus
frequently take four or five seconds. That may not seem very long, but I find it very
irritating. I'm not sure why the AirMap is so much faster than the other two — it might
have a faster microprocessor or more efficient software, I can't tell. But whatever magic
Lowrance is using to make the AirMap perform so fast, I think that Garmin and II Morrow
should pay attention.
All three models also offer an "auto-zoom" feature that lets the software
automatically adjust the zoom range to display your current route segment, zooming in
automatically as you near the fix, and zooming out once you've passed the fix to let you
see the next route segment. This is an extremely useful feature and I find myself using it
most of the time when in-flight. When auto-zoom is active, the speed of the AirMap's map
processing (and the slowness of the Garmin's and Precedus's) are especially obvious
because the zoom range is changing so frequently (particularly as you approach a fix). The
Garmin is especially distracting in this regard, constantly popping up its
"Loading..." message at the worst possible time.
Garmin explained to me why the -195's map redrawing speed is so much slower than the
AirMap's. It turns out that the -195 software generates not just one but five
screens worth of map each time you zoom: the visible screen, plus a screen's worth of
unseen map data to the left, right, above and below the visible screen! This is needed to
support the Garmin's "smooth-scroll" panning feature (described below). Coupled
with the fact that the Garmin's screen is 50% larger than the AirMap's, and that its map
is considerably more detailed, it's no wonder that its map redrawing speed is so slow.
Nevertheless, understanding the reason doesn't make it any less annoying.
Another area where the Garmin software needs work occurs as you approach your
destination airport with auto-zoom enabled. With all three models, the airport's runway
configuration becomes visible as you zoom in past a certain point. With the AirMap in
auto-zoom mode, this usually seems to happen at about 4 miles from the airport. The
Precedus is about the same. But with the Garmin, it seemed as if you couldn't
"see" the runways until you were nearly in the traffic pattern. (Garmin tells me
the runway layout is displayed at the 12-mile scale and below, but I sure couldn't see
it.)
Regional Mapping Cartridges
In addition to the built-in worldwide base map that comes with the AirMap and the
Garmin 195, both radios have a provision for regional mapping cartridges to be plugged in
to provide additional ground mapping detail. The AirMap cartridges are available now; the
Garmin's are not, but they're planned for sometime in the future. (The Precedus has no
cartridge slot.)
Lowrance offers cartridges for 64 different regions that cover the conterminous U.S. I
obtained the cartridge for Southern California and evaluated it in my AirMap. The
cartridge does indeed offer lots of additional ground-mapping detail, and it also seems to
fix the positional errors in highway depiction — the roads in the cartridge appear to be
spot-on.
However, the regional mapping cartridges for the AirMap seem to be useful primarily for
terrestrial and marine use, but not particularly helpful for aviation. This is because the
mapping features from the cartridge only seem to show up when the map is zoomed in below
the 10-mile range. At ranges of 10 miles and up, the display seems to be the same whether
or not the cartridge is plugged in. Since zoom ranges below 10 miles are seldom used
in-flight (except in the final few minutes of a flight as you approach the traffic
pattern), the cartridges don't help very much.
Furthermore, for a long cross-country trip (like my flight from Oshkosh to California),
you'd need a godawful number of cartridges to cover the route (probably a couple of
dozen), and you'd be too busy changing cartridges to pay much attention to the display (or
your flying). To make matters even more ridiculous, the AirMap manual stresses that the
unit should be turned off before you insert or remove a cartridge. So even if you were
inclined to carry a sackful of cartridges and change them in-flight as you fly from one
regional coverage to the next, the GPS would have to reacquire the satellites after each
cartridge change.
Bottom line: the regional cartridges may help you drive home from the airport, but they
won't do much for you in the airplane.
Garmin wasn't talking about how soon their regional cartridges would be available, how
big the coverage would be for each cartridge, how close you'd have to zoom in to see the
additional details. They did tell me that the radio doesn't have to be powered down to
change cartridges. Availability of the cartridges uncertain, but I don't much care — the
base map built into the Garmin 195 offers plenty of ground mapping detail for my needs.
De-Cluttering
One of the design challenges in any moving map display — particularly one that does
ground mapping — is how to avoid displaying so much information that the screen becomes
illegible. All three units do a decent job of de-cluttering, although frankly I think they
could do better.
The de-cluttering function of the AirMap is completely automatic and non-customizable.
In some 7,000 NM of cross-country flying with the AirMap in all sorts of areas and
conditions, I've found that it works surprisingly well. But once in a while, when flying
over sparsely-populated areas, the screen gets rather sparse and I wish I could ask the
AirMap to display some more detail. And occasionally when flying in especially complex and
densely-packed airspace (like Southern California), the screen gets a bit cluttered and I
wish I could drop out a bit of detail. Unfortunately, there's no way to do this with the
AirMap.
Both the Precedus and the Garmin 195 do permit the user to customize the de-cluttering
algorithm. But doing so involves adjusting a zillion different parameters. At what minimum
zoom range do you want to eliminate state highways? Federal highways? Interstates? City
names? Airport identifiers? VOR identifiers? Intersections? Class D airspace rings? And so
forth. Get the picture? It's so complicated to customize the de-cluttering algorithm that
in practice, I'm never inclined to fool with it.
In my humble opinion, what all three units need is a simple way for the user to say
"show me a little bit more detail" or "show me a little bit less" or
"go back to the default." I hope the crack software engineers at Garmin,
Lowrance and II Morrow are listening.
Cursor/Pan Mode
All three models have the capability of slewing a cursor around the map. This is used
for two purposes: to point to something on the map (usually an airport, fix, or airspace
boundary) in order to get more information about it or to navigate there, or to
"pan" the map window by slewing the cursor beyond the edge of the map. This is
an important and often-used feature, and each model implements it somewhat differently.
The AirMap has a particularly nice cursor mode. To activate it, you simply press any of
the four arrow keys while any map page is being displayed. Crosshairs appear, and you can
easily and precisely slew them to any location on the map with the arrow keys. If you slew
the cursor close to any edge of the map, the map is redrawn (after a one-second delay)
centered on the cursor position. Once you've placed the cursor where you want it, you can
ask the AirMap to:
- Navigate a great-circle route to the cursor position
- Drop an icon onto the map at the cursor position for future reference
- Create a user-defined waypoint at the cursor position
- Search for the nearest airports, VORs, NDBs, etc. relative to the cursor position
- Identify any special-use airspace that contains the cursor position
- Zoom the map in on the cursor position to have a closer look
To leave cursor mode, you press the "exit" key. The map resumes its previous
zoom level (or auto-zoom, if that was in effect) and re-centers on your present position.
The Garmin 195's cursor mode operates in a very similar fashion to the AirMap (so much
so that you'd swear Garmin copied it), but there are a few differences worth noting. I
found positioning the cursor more difficult with the Garmin than the AirMap's. The Garmin
uses a sort of "bullseye" symbol as its cursor (instead of crosshairs), and I
had some difficulty with this cursor symbol obscuring the map items that I was trying to
point at.
In addition, I'd often find that while slewing the cursor with the Garmin's four-way
rocker, the cursor would sometimes continue to "coast" for a short time after I
released the key, overshooting my desired location. This never happens on the AirMap, and
may be another indication that the Garmin's microprocessor is slower and less responsive
than the AirMap's. (Garmin says this "cursor coasting" problem is known and
being addressed.)
When you slew the Garmin's cursor off the edge of the map window, it behaves
differently than the AirMap. If you slew the cursor only a short distance beyond the edge
of the map window, the whole map smooth-scrolls as necessary to keep the cursor
on-screen...very nice! But if you slew the cursor significantly further, the radio puts up
that loathesome "Loading" message for 4 or 5 seconds while it recalculates five
screenfuls of map data...ugh!
An outstanding feature of the Garmin's cursor mode is that when you touch any map
feature with the cursor, up pops a little label telling you what it is. If you touch an
airport symbol, it's identifier appears. If you touch a highway, its route number pops up.
And if you touch a river or railroad track, it actually pops up a little label that says
"Russian River" or "Union Pacific RR" or whatever. Now that's really
slick!
But surprisingly, if you press the Garmin's "nrst" key while in cursor mode,
it displays a list of nearest airports to your present position, not the cursor
position. I like the AirMap's way of doing this a lot better. Another nasty glitch in the
Garmin's cursor mode: if you slew the cursor somewhere and then zoom-in for a closer look,
when you cancel cursor mode (by pressing "quit") the map doesn't return to its
previous zoom level. Very annoying. I figured this was an oversight in the software, but
Garmin seems to think it's a feature...go figure!
The Precedus calls its cursor mode "pan mode" and you enter and leave it by
pressing the "enter" key while the full-screen map page is on the display. Once
in pan mode, a little plus-sign appears on the map, and you can slew it around with the
arrow keys. If you touch any airport or navaid with the cursor, its identifier is
highlighted and you can get additional information about it by pressing the
"info" key. If you touch any special-use-airspace boundary with the cursor, it
intensifies — you can then press the "info" key and see information about that
SUA region (name, altitude limits, controlling agency, etc.). The SUA information page
even includes a perspective drawing of the SUA area which you can rotate and tilt, but I
consider this mostly a gimmick and not particularly useful — some software engineer at II
Morrow must have had too much time on his hands!
If you slew the cursor beyond the edge of the map window, the Precedus locks up for 4
or 5 seconds while it's constructing a new map display. The same thing happens whenever
you enter or leave pan mode. I find these delays very annoying. Also, the lack of
dedicated zoom-in/zoom-out keys on the Precedus makes it very difficult to zoom the
display while in pan mode. Prior to software version 5.1, it was literally impossible; in
later versions, there's a way to zoom, but it involves moving the cursor to a particular
location on the screen and is extremely awkward. Finally, in the 6.1 software update, the
II Morrow engineers fixed the pan/zoom mode so it's actually reasonable to use..
Route Mode
All three models offer a route mode which enable you to set up multi-waypoint routes
and have the GPS automatically sequence from segment to segment as you fly. All allow you
to store up to 20 such routes in memory, and to fly the routes either forwards or
backward. Since I fly mostly IFR and largely on airways, this is a feature that I use a
great deal. All three units do a good job here, but there are a few differences.
All three units have a route editor that lets you create and modify routes. I found the
route editor in the Precedus to be the easiest to master, and the one in the Garmin to be
the most confusing (at least at first). My loaner GPSMAP-195 didn't have a manual with it,
but I've talked to a couple of 195 owners who had difficulty figuring out the route editor
even after reading the manual. I think Garmin needs to make a few software tweaks in this
area.
When flying a route and approaching an intermediate fix, it's nice to know the magnetic
course of the next leg before actually reaching the fix so you can lead the turn — the
faster the airplane, the more important this is. The Precedus and AirMap both offer a
"turn anticipation" feature when route mode is active. I like the way the
Precedus does this best: at a user-programmable distance from the fix, it displays an
arrival alert which includes the identifier, course, and distance to the succeeding fix.
The AirMap also has an arrival alert with a user-programmable lead distance, but its alert
message doesn't include the next fix or course — instead, it simply sequences to the next
leg at the lead point, making the next leg info available on the normal nav pages. The
Garmin 195 has an arrival alert, but it lacks any turn-anticipation information (other
than requiring you to switch to the route page and look it up); hopefully, Garmin will
emulate the Precedus' approach in a future software update.
Approaches
One of the niftiest capabilities of the Precedus is its "approach monitor"
feature. This works in conjunction with the route mode, and lets you automatically set up
an approach at the destination airport of the route. You can choose from any published GPS
approach for the destination airport, or you can select a do-it-yourself approach that
starts at a fix 4 miles out on the extended centerline of any runway. While no handheld
GPS is certified for instrument approaches (and probably never will be), I find this
capability to be extremely useful for maintaining positional awareness while flying VFR at
night or in hazy conditions.
The Garmin 195 provides a similar capability, but it's limited to published GPS
approaches and lacks the runway centerline extension feature. This limits its utility
considerably compared to the Precedus. Lots of airports have no published GPS approaches
at all, but all have runway centerlines. (Garmin indicated that they intentionally avoided
emulating the Precedus' runway-extension feature because Garmin considered it potentially
dangerous.)
Unfortunately, the AirMap offers no approach capability at all, but does offer
centerline extensions.
Airport Information
All three models offer airport information such as field elevation, runway diagrams,
runway lengths, and frequencies for ATIS, tower, ground, clearance, AWOS, UNICOM, and
CTAF. All do a good job here, but the Precedus is the easiest to use (it has a dedicated
"info" key) and offers the most complete information, including approach and
departure control frequencies and even a sunrise/sunset calculator.
Nearest Waypoint Search
All three models offer a nearest waypoint search, but the one implemented by the
Precedus is the most comprehensive. The Precedus displays up to 40 nearest items in each
of the following categories: airports, VORs, NDBs, intersections, special-use airspace
areas, cities, and user-defined waypoints. What's more, it somehow manages to come up them
virtually instantaneously.
The AirMap search displays up to 40 nearest waypoints in each of the following
categories: airports, VORs, NDBs, intersections and user-defined waypoints. The AirMap
takes several seconds to come up with each list. A very useful feature unique to the
AirMap is the ability to perform a nearest-waypoint search centered on any desired cursor
position (rather than just from the present GPS position).
The Garmin 195 search displays the 9 nearest airports to the present GPS position.
Pressing the menu key at this point allows you to access nearest waypoints of other
categories.
User-Defined Waypoints
All models allow you to define hundreds of user-defined waypoints. But surprisingly,
neither the AirMap nor the Garmin let you define a waypoint as a radial and distance from
a VOR or other known fix — only the Precedus lets you do this. And the Precedus doesn't
allow you to define a waypoint based on cursor position — both the AirMap and Garmin do.
The inability to define a waypoint based on radial and distance is a particular problem
for instrument pilots like me, because ATC frequently specifies routings in that fashion.
Even my seven-year-old loran knows how to do this, so it's amazing that two bleeding-edge
GPS's don't. Hopefully, Garmin and Lowrance will see fit to add this capability in a
future software release. (Garmin says they're planning this in the next release.)
HSI Page
The Garmin 195 and AirMap both include an interesting "HSI" page that is
particularly useful for intercepting airways and radials, flying holding patterns, and
providing backup guidance during instrument approaches.
The Garmin HSI page looks precisely like a real horizontal situation indicator
instrument, complete with compass rose, course arrow, heading bug, lubber line, and
rectilinear CDI needle. If you're used to flying a real HSI, you'll adapt to the Garmin's
electronic version instantly.
The AirMap's HSI page only vaguely resembles a real HSI. It's more like peering through
a window in the belly of the airplane and looking down on a "road" that portrays
the desired route. The centerline is visible, as are the edges of the route (which
represent full-scale CDI deflection) and the aircraft's actual track history. You can also
watch route fixes as they pass by below. It's useful, but not nearly as nice as the
Garmin.
The Precedus now has an HSI page that is very similar to the one on the Garmin 195.
Vertical Navigation
The Garmin 195 and AirMap both offer a vertical navigation feature that helps you plan
letdowns from altitude. To use it, you bring up a setup page and specify what altitude you
want to descend to (generally pattern altitude or initial approach altitude), how far from
the airport you want to reach that altitude (4 miles seems to be a good figure), and how
rapidly you want to descend (I used 800 feet per minute).
The Garmin monitors your GPS altitude (which is not terribly accurate, but is good
enough for this purpose) and alerts you when it thinks you need to start down. You can
then switch to the HSI page, on which a "glideslope" needle appears to guide you
down. (Garmin prefers to avoid the word "glideslope" for fear some yo-yo will
try to shoot a precision approach with it...and in fact, the software shuts off the VNAV
indicator 500 feet above the target altitude.) There's also a numeric readout that
continuously shows you the descent rate necessary to get to the preprogrammed location and
altitude.
I found this feature particularly useful during the flight home from Oshkosh, because
it involved two descents from FL180 that needed to be started quite far in advance.
Although I've become pretty adept at calculating such descents in my head, I liked the
Garmin's VNAV capability and would probably use it regularly if I owned a 195.
Lowrance added VNAV capability to the AirMap in the version 1.9 software upgrade, but
it offers only a digital readout of the target altitude, rather than the "simulated
glideslope needle" display of the Garmin.
The Precedus displays GPS altitude, but doesn't have any VNAV function.
GPS Initialization
When you first fire up any of the units out of the box, you're instructed to give the
GPS receiver a rough idea of where it's located so it knows what satellites to look for
and can acquire position reasonably quickly. You're supposed to do the same thing anytime
the unit is relocated by more than about 300 miles while turned off. If you don't do this,
the receivers can use a "cold start" procedure to figure out where they are, but
this can take as much as 10 or 15 minutes.
Initializing the Precedus is a bit awkward, because you have to specify the initial
position in terms of latitude and longitude. If you don't have an approach plate handy,
you can use the GPS itself to look up a nearby airport, write down the lat/lon, and then
enter those number onto the GPS setup page. But this seems ridiculous. Why doesn't the
software simply let you enter an airport identifier on the initialization page and skip
the lat/lon nonsense?
The Garmin 195 has an even niftier way of handling this problem. When you select GPS
initialization function, the unit displays a map of North America at an extremely wide
scale (3000 NM). All you need to do is to slew a little arrow to the general vicinity of
your present position, and the GPS has what it needs to perform a rapid acquisition of
satellites. A very nice touch, I think.
The AirMap allows initializing in both ways: by pointing at the map (like the -195), or
by entering a lat/lon (like the Precedus).
GPS Receiver Performance
The original AirMap had a 5-channel GPS receiver, but Lowrance upgraded to a 12-channel
engine when it introduced the AirMap 300 in January 1998. The Precedus has an 8-channel
receiver and the Garmin has a 12-channel receiver. How much difference does this make, if
any?
All three units performed very well in actual flight conditions, using the supplied
antenna remotely mounted on the glareshield or suction-cupped to the windshield. The
5-channel AirMap and Precedus have lost position only rarely in all the time I've flown
with them, and usually reaquired position within seconds. I've never seen the 12-channel
units (Garmin or AirMap 300) lose position fix.
To make things more difficult, I ran some tests with the three units side-by-side under
marginal reception conditions (on a picnic table in my backyard, under a big oak tree that
seriously degraded reception) and timed how long they took to acquire a fix. I also forced
losses of position (by covering the antenna with my hand) and then timed how long they
took to reacquire.
The Garmin consistently acquired its fix most quickly after power-up. It always
acquired within 45 seconds, and usually within 20 seconds. The 12-channel AirMap 300 was
about the same. The older 5-channel AirMap was a bit slower, typically taking 50 seconds
or so to acquire a fix. The Precedus was slowest, taking 90 seconds and sometimes even
more to acquire. It's not clear that these differences are really significant, however. If
you power up any of these units at engine start, all will have locked on long before you
have time to taxi out and do a runup.
In-flight loss of position is more significant. Here again, the 12-channel units
(Garmin and AirMap 300) really shined — it was very difficult to get it to lose position
in my (admittedly unscientific) tests. The Precedus was slightly less resistant to losing
position, and the 5-channel AirMap was the least resistant. These results correlate
directly with the number of receiver channels, and that makes sense when you think about
it. A GPS receiver needs to be tracking four satellites in order to calculate a 3D fix, or
three satellites to calculate a 2D fix. The more satellites in addition to that minimum of
three or four that the receiver can track, the less likely it is that it will lose
position if reception of one or more satellites are lost. The 5-channel AirMap tracks only
two "extra" satellites beyond the minimum of three required, while the 8-channel
Precedus tracks five "extras" and the 12-channel Garmin and AirMap 300 can
simultaneously track every visible satellite in the sky. But despite these worst-case test
results, I must emphasize that I've flown a lot with the 5-channel AirMap and found it to
do a great job under actual flight conditions.
After an artificially-induced loss of signal, all three receivers did an excellent job
of reacquiring their position quickly. The 12-channel units (Garmin and AirMap 300)
usually reacquired in 10 seconds, the 5-channel AirMap in 20 seconds, and the Precedus in
30 seconds. Once again, these tests were done under unusually poor signal conditions
(under the tree).
Summary and Recommendations
All three of these models are truly outstanding, but all of them have some significant
weak points, and all have a room for improvement. Fortunately, many of the needed
improvements are in software, and all three units allow for software updates in the field.
So over the coming months, we can expect these radios to get better and better as the
manufacturers continue to release incremental software enhancements.
The Garmin GPSMAP-195 is extremely impressive, and
at $1,199 street price it should be. Its ground mapping capability is easily the best on
the market, thanks to its extraordinary 4-level gray scale display plus exceptional
attention to detail in its mapping software. It also has many other innovative features,
and a red-hot 12-channel GPS receiver.
My biggest gripes with the new Garmin are its brick-like size (it barely qualifies as a
handheld in my book), its high-mounted keypad and low-mounted display (bass-ackwards for
yoke-mounted use to my way of thinking), and its painfully slow response to zoom and pan
requests. They've made some improvements in this last area in a recent software update. I
also don't care for the fact that the Garmin's optional ni-cad battery pack cannot be
recharged in-flight.
The II Morrow Precedus is a first-rate, highly
refined GPS that does almost everything superbly — except ground mapping. Its sleek, slim
cellphone-like styling, high-contrast display and large oval keys make it a real pleasure
to use while handheld or yoke-mounted. I really like its approach monitor feature, its
easy-to-use interface, and its rechargeable cellphone battery.
The principal deficiency of the Precedus is its lack of gray scale display capability
for ground mapping. Its pan/zoom capability used to be very cumbersome, but this has been
fixed in the v6.1 software release.
At $995 street price, the Precedus is a decent buy.
Priced a whopping $400 less than the Garmin 195 and $200 less than
the Precedus, the Lowrance AirMap 300 at $799 easily offers the
"best bang for the buck" of any unit tested. Although the AirMap's ground
mapping isn't quite as attractive as the Garmin, it's still darn good. The AirMap also has
a better cursor mode, much faster zooms and pans than the competition, and some novel
features such as dual-map pages. It's upgraded 12-channel GPS receiver is every bit as
good as Garmin's. I also like its system for database and software updates (via cartridge
rather than PC download).
Weakest points of the AirMap are its Velcro yoke mount (which I consider adequate only
if you operate the unit without the battery pack installed), cheaper-looking plastic case,
lack of approach monitor capability, and a user interface that is not quite as easy to
learn or use as the other units. Lowrance has gradually been improving the
user-friendliness of this unit (as well as its feature set) through a succession of
software upgrades.
Recommendations
If you want the best ground mapping available, the Garmin GPSMAP-195 is your obvious
choice. If you're on a budget, the Lowrance AirMap 300 is an excellent radio at an
unbeatable price. And if you're not mesmerized by ground mapping and prefer a more compact
unit, the Precedus is still a superb GPS and II Morrow keeps making it better and better.
It's hard to go wrong with any of these models — they all do a great job.
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