Three Ground-Mapping GPS Handhelds

It was April 1996 when Lowrance Electronics stood the aviation GPS market on its ear by introducing the AirMap, the first handheld aviation GPS with built-in ground-mapping capability. Now, pilots have three ground-mapping competitors to choose from: the AirMap 300, the Garmin GPSMAP-195, and the upgraded II Morrow Precedus. We've put all three through their paces on a long IFR X-C trip, and here's our in-depth evaluation.


ProductsNOTE: Since this comparison was originally written, Garmin introduced itslower-priced GPS III Pilot which also has ground-mapping capability. We’ve reviewed thisunit in a separate article. Lowrance subsequently introducedits own lower-priced unit, the AirMap 100, which we’ve also reviewedseparately.

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Change History

  • 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)

Ground Mapping … What’s the Big Deal?

I must admit that when I first set eyes on the Lowrance AirMap in May, Iwas 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 payingattention 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, particularlythe Garmin GPS-90 and the II Morrow Precedus, and also flown behind the Argus 5000 and7000 panel-mount moving maps. It seemed to me that moving map displays were already toocluttered with airports, navaids and special-use airspace boundaries, especially in thecomplex and densely-packed airspace around Los Angeles and San Francisco where I oftenfly. So my first reaction was that I needed highways, waterways and other terrestrialfeatures on my moving map about as badly as I needed a third control yoke or a quadricyclelanding gear.

Lowrance AirMap But my first long IFR cross-country trip with the LowranceAirMap changed my opinion. I found that the AirMap’s display was not excessively clutteredor hard to read, despite the presence of ground mapping features. The AirMap’shigh-resolution display (with its 25,600 pixels capable of not only black and white butalso gray) and its clever de-cluttering software (which automatically drops less-importantmap 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 theflight 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, Ifound it to be a very seductive luxury. The next time I flew with a moving map that lackedground 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 March1996, showed the unit at Sun ‘n Fun in April, and started production-quantity deliveriesof customer units in May. Since then, they’ve been selling AirMaps as fast as they canmake them.

Garmin GPSMAP-195 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 productdevelopment cycle was months behind Lowrance’s and that they’d be lucky to have the 195 inproduction by Oshkosh in early August 1996. As it turned out, Garmin did deliver theirfirst 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 homefrom Oshkosh empty-handed.

IIMorrow Apollo Precedus Not wanting to be left out, II Morrow released in lateJuly 1996 an upgraded version of their Precedus handheld with mapping of highways andcities. The upgraded Precedus was in plentiful supply at Oshkosh. The ground-mappingupgrade required doubling the size of the unit’s flash memory from 2 to 4 megabytes, butII Morrow offered a hardware retrofit for owners of earlier Precedus units, and in factwas 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 Precedusat Oshkosh ’96. But there’s no way of evaluating complex products like these in a quickin-booth demo. You’ve got to take them flying, preferably on a cross-country trip ofsignificant length, to do a really meaningful review. I knew that my flight from Oshkoshback 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 exhibitorsimpatiently waiting for the end of the show, I decided to see whether I could get my handson 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 tothe latest software version (1.8 at that time). Tom Rogers of Avionics West had some ofthe upgraded Preceduses in stock and arranged for me to borrow one for the trip. TheGarmin was the most difficult to come by because they were in such short supply and allcustomer units had long-since sold out. But Bob Cusick of Garmin came to my rescue byloaning me his personal demonstrator GPSMAP-195 for the flight home, after I solemnlypromised him that I would FedEx it back to him the moment I got home. (Bob made me prickmy finger and sign my name in blood.)

Mike Busch's Cessna T310R So Thursday morning, I launched westbound from Oshkosh inmy 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. Theroute took me across the Great Plains, through the Denver Class B airspace, over theRockies, 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 acrossCalifornia’s San Joachim valley to the Pacific coast. The entire trip was made underInstrument Flight Rules. Cruising altitude was 12,000 feet from Oshkosh to Denver, andFL180 (with a cannula up my nose) for most of the remainder of the trip. The weather wasmostly clear and unrestricted, except for an area of airmass thunderstorms between Denverand 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 GPShandhelds. Here’s what I learned.

Hardware Comparison

IIMorrow Apollo Precedus Lowrance AirMap Garmin GPSMAP-195

Size and appearance

When you place the three handhelds side-by-side, the first thing you notice is a bigdifference in size. All three are about the same height: 7-1/2 inches, give or take aneighth. But the Precedus is much slimmer and more svelte than the other two. It looksrather like a cellular telephone with an oversized display, and in fact is only slightlybigger than my Mitsubishi Diamond-Tel cellphone or my ICOM IC-A22 comm transceiver. Like acellphone, the Precedus fits comfortably in one hand and is easy to operate one-handed ifyou operate the keyboard with your thumb.

The AirMap and Garmin 195 are both half-again as wide as the Precedus (roughly 3 inchesversus 2-1/8 inches). Both are uncomfortably large for one-handed operation; you findyourself either holding the radio in one hand and punching the keys with the index fingerof the other hand, or else cradling the radio in both hands and operating the keys withboth thumbs.

The Precedus and the AirMap are about the same thickness: 1-3/8 inches. The Garmin issubstantially 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 advertisingphotos. Any bigger and you really couldn’t call it a handheld. In fact, when I used theunits in my motel room (for familiarization, pre-entering routes, and so forth), I almostalways 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 ofquality. The Precedus is packaged in a cast aluminum enclosure which gives it a solid feeland a surprisingly heavy weight considering its slim proportions. The Garmin’s case isplastic, 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 1.2lbs.) 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 $995for the Precedus and $1,199 for the GPSMAP-195. In actuality, however, the AirMap seems tobe at least as rugged and well-built as the other two models. In fact, the AirMap’sunusual 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 toworry about scratching the display; with the Precedus or the Garmin 195, you have to slidethe 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 openedwithout destroying it. The Garmin’s plastic case is screwed together with a gasket andnitrogen-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 memoryrequired for the mapping upgrade.

Displays: Precedus, AirMap 300, GPSMAP-195


Perhaps the most significant hardware differences among the three units relate to theirLCD displays. The Precedus, which was designed without ground mapping in mind, has a tallrectangular 1-3/8 by 2-7/8 inch display with 12,800-pixel resolution (80 by 160). With itsintense blue color and large .45-millimeter pixel size, the Precedus display has the bestcontrast and readability of the three units over a wide range of lighting conditions andviewing angles, particularly in direct sunlight. But its lack of gray-scale capabilityseverely 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 twicethat of the Precedus: 25,600 pixels (160 by 160). Each .35-millimeter pixel has 3-levelgray scale capability (black, white, or gray). This greatly enhances its ground mappingcapability, since mapping features like lakes, rivers and ATC rings can be shown in graywithout 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 whenoperating the AirMap in split-screen mode where the left half of the screen displays amoving map and the right half displays alphanumeric flight data. In this mode, theAirMap’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’shalf-screen map is far more legible than the Precedus’s full-screen map. Gray scale is thedifference.

The Garmin GPSMAP-195 display goes even further. It has exactly the same width andpixel size as the AirMap, but is half again as tall: 2-1/4 by 3-3/8 inches and 38,400pixels (160 by 240). Perhaps even more important, the Garmin’s display supports 4-levelgray scale (black, dark gray, light gray, white), giving the GPSMAP-195 an even betterability to display dense ground mapping information while still remaining legible.

The downside of these gray-scale displays is impaired contrast and a narrower viewingangle. I found both the AirMap and the Garmin 195 displays difficult to read clearly indirect sunlight. Usually, an adjustment to the display’s contrast setting solved theproblem, but when the lighting conditions changed, the contrast needed to be adjustedagain. Although the blue-and-white display on the Precedus also has adjustable contrast, Inever needed to fiddle with it.

All three units have backlit displays for night use. The Precedus and Garmin 195 bothhave white backlighting with three intensity levels (high, medium, low). The AirMap usesgreen backlighting with 16 intensity levels. All three are a real pleasure to use atnight, particularly when operating off aircraft power so that the backlight can remain oncontinuously. When operating off battery power, all models extinguish their backlightafter a time-out to maximize battery life.


The differences in keypad design of the three models are not as obvious at first glanceas the differences in their displays. But the importance of keypad layout and positionbecomes clear after you’ve flown with the units for awhile, particularly at night and inturbulence.

Precedus keypad The Precedus uses a simple 3-by-3 keypad layout, with nine largeoval fingertip-sized keys located at the extreme bottom of the faceplate. Its large keysare wonderful for one-handed operation (when your thumb is the only finger available), andfor use in turbulence. At night, they keys are magnificently backlit, appearing as glowingovals with white legends. But nine keys don’t seem to be quite enough. I wish II Morrowhad added one more row of keys, like a telephone keypad. The absence of dedicatedzoom-out/zoom-in keys and a “cancel” key are particularly noticeable.

GPSMAP-195 keypad The Garmin 195 has plenty of keys – eight small chicklet-stylefunction keys, plus a two-way zoom-in/zoom-out rocker key and a four-wayleft-right-up-down cursor control rocker – essentially 14 separate keys. The keys arelogically 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 thanthe four separate arrow keys used by the Precedus and AirMap. And sometimes I would haveto press a key two or three times before the Garmin would recognize my keypad input; Icouldn’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 – intentionallyor otherwise – and times out, the first keypress of any key turns the backlighting on anddoesn’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 inboth hands and operating the keys with your thumbs. But when the radio is in its yokemount (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-mountedkeypad dictated a bottom-mounted display, which I found to be too low for comfortableviewing during yoke-mounted operation. I often found myself having to tilt up the yokemount to get a better view of the screen, which unfortunately causes the radio to obscurethe instrument panel.

AirMap keypad The AirMap 300 keypad splits the difference between the Precedus andthe Garmin. It has twelve keys, and is placed right in the middle of the unit, below thedisplay and above the battery pack. This placement works well for both handheld andyoke-mounted operation. The keys are black with white legends, and at night the backlightmakes them glow a luminous green. I only wish the keys were a bit larger – there seems tobe plenty of room in the AirMap’s keypad layout for big, Precedus-sized keys.


Like the cellular phone that it resembles, the Precedus comes with a quick-changerechargeable ni-cad battery pack and a wall-transformer-type charger. In fact, the batterypack used by the Precedus is a standard NEC cellphone battery, so replacement batterypacks are readily available anyplace that carries NEC phones. The standard battery is goodfor about 4 hours, but high-capacity packs offering 6 hours to a charge are alsoavailable.

The Garmin 195 comes with a battery case designed to hold six AA-size alkalinebatteries, which Garmin claims will last “up to 10 hours” if backlighting is notused, although that figure seems a bit optimistic based on my tests. Garmin also offers anoptional rechargeable ni-cad battery pack with an AC charger, which they claim will lastup to 9 hours to a charge. But there is no provision for charging the pack in-flight whilethe GPS is being powered from the aircraft electrical system…a serious shortcoming in myview. In the event of an in-flight electrical failure, the Garmin’s battery might easilystart out with less than a full charge. Consequently, the ni-cad option on the Garmin 195might not be such a good idea unless you also carry an alkaline battery pack loaded withsix fresh AA’s as a backup.

The AirMap 300 has the most flexible power system of all. It comes standard with twobattery 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 fromthe “memory effect” that plagues ni-cads, can be recharged in-flight while theGPS 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 variesfrom 4 to 10 hours, depending on what update rate is configured. The AirMap can also berun off aircraft power with the battery pack removed, reducing the size of the unit bynearly half and making it extremely compact.

Opinions are divided concerning whether alkalines or rechargeables (ni-cad or NiMH) arethe better power source for a handheld GPS. Many pilots prefer alkalines because they haveexcellent shelf-life, provide about twice the running time of ni-cads, and are availableat any drugstore or supermarket. I prefer rechargeables because I normally fly with theGPS plugged into aircraft power, so battery operation is only an issue for me duringground use or in the event of an in-flight electrical failure – and in either case, 4hours is plenty. Good quality AA alkalines (I prefer Duracells) cost a dollar or moreapiece, so a new set of alkalines for the AirMap or Garmin 195 costs at least six bucks.


All three models use a flat patch-style GPS antenna. The Precedus and Garmin 195 use anantenna 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 aprotective 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 aremote-mounted antenna located on the glareshield or suction-cup-mounted to thewindshield. All three models allow for this, but in different ways. Both the Precedus andthe AirMap allow their attached antennas to be removed from the radio and mounted in asuitable location, and both include a coaxial cable for hooking the remote-mounted antennato the radio. The antenna on the Precedus slides off and back on very easily. The flip-topAirMap antenna used to be rather a pain to detach and reattach, but Lowrance redesignedthe antenna attachment scheme in the spring of 1997, and owners of earlier models canretrofit their thumbwheel-type units easily. The Garmin 195 offers the best solutionof 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 comewith 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 withthe Precedus best by far: it’s small, sleek and elegant (like the radio itself) andsomething you don’t mind leaving in the airplane permanently (again, assuming you ownone). 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). Aknob on the mount is used to lock and release the radio. The cigarette lighter power cordscrews onto a couple of little ears on the yoke mount and automatically engages the powerconnector on the 195 when it is locked into the mount. I found, however, that the powerconnector doesn’t make reliable contact unless you’re very careful about how you insertthe radio into the yoke mount. This isn’t a big problem once you’re aware of it, but itdefinitely can bite the novice user. The Garmin does display an icon at the bottom of thescreen 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 thatthe Velcro simply isn’t strong enough (or perhaps not enough of it is used) to hold theAirMap 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-mountedAirMap might become a projectile in severe turbulence (although it did hang on okay when Iflew through some moderate bumps). With the battery detached and running solely onaircraft 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 canbe updated in the field. The Precedus and Garmin 195 are both updated by hooking the radioto 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 worksfine, we have two beefs with it. First, both II Morrow and Garmin classify the data cableand 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 anIBM-compatible PC, you’re out of luck. (Macintosh owners might get away with using a PCemulator 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 andsoftware 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 newone, and send the old one back to Lowrance in the special mailer that comes with theupdate. Software updates are slightly different: you plug the software cartridge into theAirMap and turn it on, whereupon it automatically loads the new software into its internalflash memory; then you unplug the software cartridge and mail it back to Lowrance. No PCor cable is required. Furthermore, Lowrance charges substantially less for its Jeppesendatabase 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 thePrecedus at Oshkosh ’95, and has been continuously refining and enhancing its softwaresince then, and owners of even the earliest Precedus units have been able to benefit fromthe improvements. Lowrance and Garmin have both released a number of improved softwarerefinements, and the enhancements are likely to continue.


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 pressesthe “menu” key. You select a menu function by moving the cursor to the desireditem with the up/down arrow keys, then pressing the “enter” key. The top menuitem is “Return to Nav” which takes you back to the navigation/map pages. Theother 12 menu items call up specialized pages that permit you to configure the varioussystem and mapping functions, initialize the GPS position and clock, start and stoptimers, perform E6B functions, access checklists, and so forth. For the most part, thePrecedus 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 orless, depending on what feature are active) but only 6 of them are visible in the menuwindow at a time – the rest much be reached by scrolling as you move the cursor throughthe menu using the up/down arrow keys. I found the inability to see the entire menu atonce makes the AirMap a bit more difficult to learn and use, although it’s not a majorobstacle. 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” keybrings up one of several alternative menus, depending on what nav page is being displayedwhen you press the key. If you press “menu” while looking at the map page, forexample, a map-option menu pops up; if you do the same thing while looking at the activeroute page, a route-option menu pops up instead; and so forth. Regardless of which menupops 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 itsaves 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 fewitems, and they are displayed in a larger, easier-to-read font than the Precedus orAirMap. Menu items that are inapplicable in the present context are “grayedout”, 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 andfour alphanumeric nav pages, each containing up to twelve fields that you can select froma palette of 34 different nav-info items. You can also customize the four fields on thesplit-screen page in the same fashion.

When the Precedus is in navigation mode (as it is most of the time), you cycle throughthese various nav pages by pressing the up- and down-arrow keys. The left- and right-arrowkeys are used to zoom the map pages in and out. In flight, I find myself togglingfrequently back and forth between the split-screen map page (which I’ve configured to showdistance-to-waypoint, groundspeed, bearing and track) and one of the alphanumeric navpages (to see CDI, time-to-station and time-to-destination, among other items). This isn’tparticularly difficult to do, but I’ve often wished for more than four nav-info fields onthe Precedus split-screen page. (II Morrow’s software whizzes could have accomplished thiseasily, simply by using a smaller font for the nav-info. But then I’m sure they’d havegotten 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 importantdifferences. It has only one map page and one alphanumeric nav-info page, but that’senough because its screen is so big that it can get three times as much information on apage as the Precedus can. The Garmin does offer an interesting “HSI” page thathas no parallel on the Precedus. This makes a total of six nav pages in all, which you cancycle through by pressing the “page” key. (The “quit” key cyclesthrough them backwards.) Map zooming is accomplished with the dedicated zoom-in/zoom-outrocker key. This leaves the four-way cursor control rocker free for slewing the cursoraround the map (discussed below).

Like the Precedus, the Garmin allows user customization of all the nav-info fields froma lengthy palette of choices. It also allows its single map page to be customized: you canselect a full-screen map or a variety of split-screen options with 2, 4, 6 or 8 nav-infofields, or with 0, 2, 4 or 6 fields plus a CDI display. I settled on a split-screenconfiguration with 6 nav-info fields plus a CDI display. That proved sufficient to displayalmost all of the nav-data I needed to fly with, and still left enough screen space for avery respectable (AirMap-sized) moving map. With this configuration, I found that I almostnever needed to toggle to another nav page except when using some exotic feature such asVNAV.

The AirMap works a bit differently. It offers a tremendous variety of different navpage layouts – 21 different pages if I counted correctly – most of themuser-customizable. In addition to the usual map, alphanumeric, and split-screen pages, theAirMap offers a variety of dual-map screen layouts, where each map is individuallyconfigurable and zoomable. Just to cite one example: you can bring up a display where theleft half of the screen is an ordinary moving map, the upper-right-hand quadrant is asecond map zoomed in tightly on the destination airport, and the lower-right-hand quadrantdisplays 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 ofthem to simply cycle through sequentially like the Precedus and Garmin do. To change navpages on the AirMap, you press the “mode” key to bring up a menu of pages, thenuse 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 sixor seven pages with a single key. Second, customizing the pages on the AirMap is moredifficult 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 featureof a handheld GPS, not an essential one. I certainly wouldn’t choose which one to buystrictly on the basis of its ground mapping capability alone. But if ground mapping isyour 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 softwareengineers have managed to create a moving map that looks astonishingly like a sectionalchart. Highways, rivers and lakes look very much like they would on a chart. Railroadtracks are distinguishable from roads by their little tick marks. Major metropolitan areasare 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 evenoriented in the direction of the longest runway. VORs are depicted using the familiarhexagonal VOR symbol (sans compass rose), and even indicate whether the navaid hasDME 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 wouldbe 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 crediblejob. The AirMap’s display, while only 2/3 the size of the Garmin’s, is still plenty bigand capable for the task. But the AirMap’s marine heritage is obvious. Its standardbackground map depicts rivers, lakes and coastlines in faithful detail, but highways aresometimes 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 depictthem using standard aviation symbology. In short, I found the AirMap’s ground mappingcapability 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 newcapability to the AirMap: an obstacle database, and mapping of obstacles. Antenna towersand the like now show up on the map, complete with their elevations (you can specify MSLor AGL). This is a very useful safety feature, and one that the competition is sure tonotice.

The Precedus comes in a very distant third in the ground mapping department. Itsrelatively small, non-gray-scale display was never designed for such a task. It’s simplyimpossible to depict very much ground mapping information on a display like that withoutit becoming too cluttered to read. The Precedus ground mapping capability is limited tohighways and city names – no rivers, or lakes are depicted, nor railroad tracks. In theversion 6.1 software upgrade, the Precedus added coastlines and territorial/politicalboundaries to the map.

This is not to say that II Morrow’s highway mapping upgrade to the Precedus isn’t aworthwhile 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 limitationsof the Precedus display hardware make it impossible for this unit to compete with unitslike 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 orientednorth-up, track-up, or course-up. On the AirMap’s dual-map pages, you can set theorientations 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 “northindicator” to give you a general idea of which way the map is oriented. (The Precedusdoesn’t.) Both the Precedus and the Garmin display the little airplane symbol thatrepresents your present position about 3/4 of the way down the screen, so the map viewfocuses on where you’re going rather than where you’ve been. The AirMap puts the airplanesymbol 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 ofscales. The AirMap zoom goes from screen widths of 0.1 NM to 4,000 NM, and the Garmin goesfrom 0.1 NM to 3,000 NM. The maximum zoom-out lets you see the entire North Americancontinent at once – the maximum zoom-in would let you taxi to the correct tiedown inzero-zero conditions (if it weren’t for the DOD’s Selective Availability program thatintentionally degrades GPS accuracy). Both units have dedicated zoom-in/zoom-out keys onthe keypad to control this function.

The Precedus zoom goes from 0.1 NM to 250 NM. The lack of extreme zoom-out isinconsequential for in-flight use (where ranges of 5 to 150 NM are typically used). But itis occasionally useful during flight planning on the ground; e.g., to answer questionslike “does my route from Cincinnati to Tulsa pass through Arkansas?” Not a bigissue. The Precedus doesn’t have dedicated zoom keys, and uses the left- and right-arrowkeys instead.

When you zoom in or out on any of these models, there’s a delay while themicroprocessor constructs the new map. And because I tend to zoom in and out a lot inflight, 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 displaythe new map after a zoom-in or zoom-out request, while both the Garmin and the Precedusfrequently take four or five seconds. That may not seem very long, but I find it veryirritating. I’m not sure why the AirMap is so much faster than the other two – it mighthave a faster microprocessor or more efficient software, I can’t tell. But whatever magicLowrance is using to make the AirMap perform so fast, I think that Garmin and II Morrowshould pay attention.

All three models also offer an “auto-zoom” feature that lets the softwareautomatically adjust the zoom range to display your current route segment, zooming inautomatically as you near the fix, and zooming out once you’ve passed the fix to let yousee the next route segment. This is an extremely useful feature and I find myself using itmost of the time when in-flight. When auto-zoom is active, the speed of the AirMap’s mapprocessing (and the slowness of the Garmin’s and Precedus’s) are especially obviousbecause the zoom range is changing so frequently (particularly as you approach a fix). TheGarmin 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 theAirMap’s. It turns out that the -195 software generates not just one but fivescreens worth of map each time you zoom: the visible screen, plus a screen’s worth ofunseen map data to the left, right, above and below the visible screen! This is needed tosupport the Garmin’s “smooth-scroll” panning feature (described below). Coupledwith the fact that the Garmin’s screen is 50% larger than the AirMap’s, and that its mapis 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 yourdestination airport with auto-zoom enabled. With all three models, the airport’s runwayconfiguration becomes visible as you zoom in past a certain point. With the AirMap inauto-zoom mode, this usually seems to happen at about 4 miles from the airport. ThePrecedus 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 methe runway layout is displayed at the 12-mile scale and below, but I sure couldn’t seeit.)

Regional Mapping Cartridges

In addition to the built-in worldwide base map that comes with the AirMap and theGarmin 195, both radios have a provision for regional mapping cartridges to be plugged into provide additional ground mapping detail. The AirMap cartridges are available now; theGarmin’s are not, but they’re planned for sometime in the future. (The Precedus has nocartridge slot.)

Lowrance offers cartridges for 64 different regions that cover the conterminous U.S. Iobtained the cartridge for Southern California and evaluated it in my AirMap. Thecartridge does indeed offer lots of additional ground-mapping detail, and it also seems tofix the positional errors in highway depiction – the roads in the cartridge appear to bespot-on.

However, the regional mapping cartridges for the AirMap seem to be useful primarily forterrestrial and marine use, but not particularly helpful for aviation. This is because themapping features from the cartridge only seem to show up when the map is zoomed in belowthe 10-mile range. At ranges of 10 miles and up, the display seems to be the same whetheror not the cartridge is plugged in. Since zoom ranges below 10 miles are seldom usedin-flight (except in the final few minutes of a flight as you approach the trafficpattern), 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 ofdozen), and you’d be too busy changing cartridges to pay much attention to the display (oryour flying). To make matters even more ridiculous, the AirMap manual stresses that theunit should be turned off before you insert or remove a cartridge. So even if you wereinclined to carry a sackful of cartridges and change them in-flight as you fly from oneregional coverage to the next, the GPS would have to reacquire the satellites after eachcartridge change.

Bottom line: the regional cartridges may help you drive home from the airport, but theywon’t do much for you in the airplane.

Garmin wasn’t talking about how soon their regional cartridges would be available, howbig the coverage would be for each cartridge, how close you’d have to zoom in to see theadditional details. They did tell me that the radio doesn’t have to be powered down tochange cartridges. Availability of the cartridges uncertain, but I don’t much care – thebase map built into the Garmin 195 offers plenty of ground mapping detail for my needs.


One of the design challenges in any moving map display – particularly one that doesground mapping – is how to avoid displaying so much information that the screen becomesillegible. All three units do a decent job of de-cluttering, although frankly I think theycould 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 andconditions, I’ve found that it works surprisingly well. But once in a while, when flyingover sparsely-populated areas, the screen gets rather sparse and I wish I could ask theAirMap to display some more detail. And occasionally when flying in especially complex anddensely-packed airspace (like Southern California), the screen gets a bit cluttered and Iwish I could drop out a bit of detail. Unfortunately, there’s no way to do this with theAirMap.

Both the Precedus and the Garmin 195 do permit the user to customize the de-clutteringalgorithm. But doing so involves adjusting a zillion different parameters. At what minimumzoom range do you want to eliminate state highways? Federal highways? Interstates? Citynames? Airport identifiers? VOR identifiers? Intersections? Class D airspace rings? And soforth. Get the picture? It’s so complicated to customize the de-cluttering algorithm thatin 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 usedfor two purposes: to point to something on the map (usually an airport, fix, or airspaceboundary) 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 isan 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 ofthe four arrow keys while any map page is being displayed. Crosshairs appear, and you caneasily and precisely slew them to any location on the map with the arrow keys. If you slewthe 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 canask 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 previouszoom 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 muchso that you’d swear Garmin copied it), but there are a few differences worth noting. Ifound positioning the cursor more difficult with the Garmin than the AirMap’s. The Garminuses a sort of “bullseye” symbol as its cursor (instead of crosshairs), and Ihad some difficulty with this cursor symbol obscuring the map items that I was trying topoint at.

In addition, I’d often find that while slewing the cursor with the Garmin’s four-wayrocker, the cursor would sometimes continue to “coast” for a short time after Ireleased the key, overshooting my desired location. This never happens on the AirMap, andmay be another indication that the Garmin’s microprocessor is slower and less responsivethan the AirMap’s. (Garmin says this “cursor coasting” problem is known andbeing addressed.)

When you slew the Garmin’s cursor off the edge of the map window, it behavesdifferently than the AirMap. If you slew the cursor only a short distance beyond the edgeof the map window, the whole map smooth-scrolls as necessary to keep the cursoron-screen…very nice! But if you slew the cursor significantly further, the radio puts upthat loathesome “Loading” message for 4 or 5 seconds while it recalculates fivescreenfuls of map data…ugh!

An outstanding feature of the Garmin’s cursor mode is that when you touch any mapfeature with the cursor, up pops a little label telling you what it is. If you touch anairport 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 reallyslick!

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 cursorposition. I like the AirMap’s way of doing this a lot better. Another nasty glitch in theGarmin’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 itsprevious zoom level. Very annoying. I figured this was an oversight in the software, butGarmin seems to think it’s a feature…go figure!

The Precedus calls its cursor mode “pan mode” and you enter and leave it bypressing the “enter” key while the full-screen map page is on the display. Oncein pan mode, a little plus-sign appears on the map, and you can slew it around with thearrow keys. If you touch any airport or navaid with the cursor, its identifier ishighlighted and you can get additional information about it by pressing the”info” key. If you touch any special-use-airspace boundary with the cursor, itintensifies – you can then press the “info” key and see information about thatSUA region (name, altitude limits, controlling agency, etc.). The SUA information pageeven includes a perspective drawing of the SUA area which you can rotate and tilt, but Iconsider this mostly a gimmick and not particularly useful – some software engineer at IIMorrow 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 4or 5 seconds while it’s constructing a new map display. The same thing happens wheneveryou enter or leave pan mode. I find these delays very annoying. Also, the lack ofdedicated zoom-in/zoom-out keys on the Precedus makes it very difficult to zoom thedisplay while in pan mode. Prior to software version 5.1, it was literally impossible; inlater versions, there’s a way to zoom, but it involves moving the cursor to a particularlocation on the screen and is extremely awkward. Finally, in the 6.1 software update, theII 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 routesand have the GPS automatically sequence from segment to segment as you fly. All allow youto store up to 20 such routes in memory, and to fly the routes either forwards orbackward. Since I fly mostly IFR and largely on airways, this is a feature that I use agreat 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 theroute editor in the Precedus to be the easiest to master, and the one in the Garmin to bethe 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 editoreven after reading the manual. I think Garmin needs to make a few software tweaks in thisarea.

When flying a route and approaching an intermediate fix, it’s nice to know the magneticcourse of the next leg before actually reaching the fix so you can lead the turn – thefaster 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 thePrecedus does this best: at a user-programmable distance from the fix, it displays anarrival 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 alertmessage doesn’t include the next fix or course – instead, it simply sequences to the nextleg at the lead point, making the next leg info available on the normal nav pages. TheGarmin 195 has an arrival alert, but it lacks any turn-anticipation information (otherthan requiring you to switch to the route page and look it up); hopefully, Garmin willemulate the Precedus’ approach in a future software update.


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 upan approach at the destination airport of the route. You can choose from any published GPSapproach for the destination airport, or you can select a do-it-yourself approach thatstarts at a fix 4 miles out on the extended centerline of any runway. While no handheldGPS is certified for instrument approaches (and probably never will be), I find thiscapability to be extremely useful for maintaining positional awareness while flying VFR atnight or in hazy conditions.

The Garmin 195 provides a similar capability, but it’s limited to published GPSapproaches and lacks the runway centerline extension feature. This limits its utilityconsiderably compared to the Precedus. Lots of airports have no published GPS approachesat all, but all have runway centerlines. (Garmin indicated that they intentionally avoidedemulating the Precedus’ runway-extension feature because Garmin considered it potentiallydangerous.)

Unfortunately, the AirMap offers no approach capability at all, but does offercenterline 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, andCTAF. 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 anddeparture control frequencies and even a sunrise/sunset calculator.

Nearest Waypoint Search

All three models offer a nearest waypoint search, but the one implemented by thePrecedus is the most comprehensive. The Precedus displays up to 40 nearest items in eachof the following categories: airports, VORs, NDBs, intersections, special-use airspaceareas, cities, and user-defined waypoints. What’s more, it somehow manages to come up themvirtually instantaneously.

The AirMap search displays up to 40 nearest waypoints in each of the followingcategories: airports, VORs, NDBs, intersections and user-defined waypoints. The AirMaptakes several seconds to come up with each list. A very useful feature unique to theAirMap is the ability to perform a nearest-waypoint search centered on any desired cursorposition (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 othercategories.

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 froma VOR or other known fix – only the Precedus lets you do this. And the Precedus doesn’tallow 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 problemfor 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-edgeGPS’s don’t. Hopefully, Garmin and Lowrance will see fit to add this capability in afuture 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 isparticularly useful for intercepting airways and radials, flying holding patterns, andproviding backup guidance during instrument approaches.

The Garmin HSI page looks precisely like a real horizontal situation indicatorinstrument, complete with compass rose, course arrow, heading bug, lubber line, andrectilinear CDI needle. If you’re used to flying a real HSI, you’ll adapt to the Garmin’selectronic version instantly.

The AirMap’s HSI page only vaguely resembles a real HSI. It’s more like peering througha window in the belly of the airplane and looking down on a “road” that portraysthe desired route. The centerline is visible, as are the edges of the route (whichrepresent full-scale CDI deflection) and the aircraft’s actual track history. You can alsowatch route fixes as they pass by below. It’s useful, but not nearly as nice as theGarmin.

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 planletdowns from altitude. To use it, you bring up a setup page and specify what altitude youwant to descend to (generally pattern altitude or initial approach altitude), how far fromthe airport you want to reach that altitude (4 miles seems to be a good figure), and howrapidly you want to descend (I used 800 feet per minute).

The Garmin monitors your GPS altitude (which is not terribly accurate, but is goodenough for this purpose) and alerts you when it thinks you need to start down. You canthen switch to the HSI page, on which a “glideslope” needle appears to guide youdown. (Garmin prefers to avoid the word “glideslope” for fear some yo-yo willtry to shoot a precision approach with it…and in fact, the software shuts off the VNAVindicator 500 feet above the target altitude.) There’s also a numeric readout thatcontinuously shows you the descent rate necessary to get to the preprogrammed location andaltitude.

I found this feature particularly useful during the flight home from Oshkosh, becauseit 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 theGarmin’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, butit offers only a digital readout of the target altitude, rather than the “simulatedglideslope 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 theGPS receiver a rough idea of where it’s located so it knows what satellites to look forand can acquire position reasonably quickly. You’re supposed to do the same thing anytimethe 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, butthis can take as much as 10 or 15 minutes.

Initializing the Precedus is a bit awkward, because you have to specify the initialposition 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 thenenter those number onto the GPS setup page. But this seems ridiculous. Why doesn’t thesoftware simply let you enter an airport identifier on the initialization page and skipthe lat/lon nonsense?

The Garmin 195 has an even niftier way of handling this problem. When you select GPSinitialization function, the unit displays a map of North America at an extremely widescale (3000 NM). All you need to do is to slew a little arrow to the general vicinity ofyour present position, and the GPS has what it needs to perform a rapid acquisition ofsatellites. A very nice touch, I think.

The AirMap allows initializing in both ways: by pointing at the map (like the -195), orby 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-channelengine when it introduced the AirMap 300 in January 1998. The Precedus has an 8-channelreceiver and the Garmin has a 12-channel receiver. How much difference does this make, ifany?

All three units performed very well in actual flight conditions, using the suppliedantenna remotely mounted on the glareshield or suction-cupped to the windshield. The5-channel AirMap and Precedus have lost position only rarely in all the time I’ve flownwith them, and usually reaquired position within seconds. I’ve never seen the 12-channelunits (Garmin or AirMap 300) lose position fix.

To make things more difficult, I ran some tests with the three units side-by-side undermarginal reception conditions (on a picnic table in my backyard, under a big oak tree thatseriously degraded reception) and timed how long they took to acquire a fix. I also forcedlosses of position (by covering the antenna with my hand) and then timed how long theytook to reacquire.

The Garmin consistently acquired its fix most quickly after power-up. It alwaysacquired within 45 seconds, and usually within 20 seconds. The 12-channel AirMap 300 wasabout the same. The older 5-channel AirMap was a bit slower, typically taking 50 secondsor so to acquire a fix. The Precedus was slowest, taking 90 seconds and sometimes evenmore to acquire. It’s not clear that these differences are really significant, however. Ifyou power up any of these units at engine start, all will have locked on long before youhave 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 positionin my (admittedly unscientific) tests. The Precedus was slightly less resistant to losingposition, and the 5-channel AirMap was the least resistant. These results correlatedirectly with the number of receiver channels, and that makes sense when you think aboutit. A GPS receiver needs to be tracking four satellites in order to calculate a 3D fix, orthree satellites to calculate a 2D fix. The more satellites in addition to that minimum ofthree or four that the receiver can track, the less likely it is that it will loseposition if reception of one or more satellites are lost. The 5-channel AirMap tracks onlytwo “extra” satellites beyond the minimum of three required, while the 8-channelPrecedus tracks five “extras” and the 12-channel Garmin and AirMap 300 cansimultaneously track every visible satellite in the sky. But despite these worst-case testresults, I must emphasize that I’ve flown a lot with the 5-channel AirMap and found it todo a great job under actual flight conditions.

After an artificially-induced loss of signal, all three receivers did an excellent jobof 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 in30 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 significantweak points, and all have a room for improvement. Fortunately, many of the neededimprovements 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 themanufacturers continue to release incremental software enhancements.

Garmin GPSMAP-195 The Garmin GPSMAP-195 is extremely impressive, andat $1,199 street price it should be. Its ground mapping capability is easily the best onthe market, thanks to its extraordinary 4-level gray scale display plus exceptionalattention 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 ahandheld in my book), its high-mounted keypad and low-mounted display (bass-ackwards foryoke-mounted use to my way of thinking), and its painfully slow response to zoom and panrequests. They’ve made some improvements in this last area in a recent software update. Ialso don’t care for the fact that the Garmin’s optional ni-cad battery pack cannot berecharged in-flight.

IIMorrow Apollo PrecedusThe II Morrow Precedus is a first-rate, highlyrefined GPS that does almost everything superbly – except ground mapping. Its sleek, slimcellphone-like styling, high-contrast display and large oval keys make it a real pleasureto use while handheld or yoke-mounted. I really like its approach monitor feature, itseasy-to-use interface, and its rechargeable cellphone battery.

The principal deficiency of the Precedus is its lack of gray scale display capabilityfor ground mapping. Its pan/zoom capability used to be very cumbersome, but this has beenfixed in the v6.1 software release.

At $995 street price, the Precedus is a decent buy.

Lowrance AirMap Priced a whopping $400 less than the Garmin 195 and $200 less thanthe Precedus, the Lowrance AirMap 300 at $799 easily offers the”best bang for the buck” of any unit tested. Although the AirMap’s groundmapping isn’t quite as attractive as the Garmin, it’s still darn good. The AirMap also hasa better cursor mode, much faster zooms and pans than the competition, and some novelfeatures such as dual-map pages. It’s upgraded 12-channel GPS receiver is every bit asgood as Garmin’s. I also like its system for database and software updates (via cartridgerather than PC download).

Weakest points of the AirMap are its Velcro yoke mount (which I consider adequate onlyif 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 tolearn or use as the other units. Lowrance has gradually been improving theuser-friendliness of this unit (as well as its feature set) through a succession ofsoftware upgrades.


If you want the best ground mapping available, the Garmin GPSMAP-195 is your obviouschoice. If you’re on a budget, the Lowrance AirMap 300 is an excellent radio at anunbeatable price. And if you’re not mesmerized by ground mapping and prefer a more compactunit, 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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