Subject: The G12 family revisions

By Dale DePriest, originally published in sci.geo.satellite-nav 26 May 1998
98/8/5 to add the G-12XL and G-48 difference data.
98/12/18 to add 4.51 differences and 1/14/99 for 4.52/3
99/4/2 to add 4.54 and G-12CX
99/5/28 add 4.53 bug.
99/6/10 add 4.55 release
99/12/22 to add information on obtaining the revision data.
00/3/7 add 4.57 release
00/5/2 added description for 4.57
00/7/31 added description for Version 3.62
00/12/2 added description for 4.58
02/9/9 added background on pre 3.5 versions.
03/8/19 added 4.60 release

Note that the version of your software/hardware is displayed on the opening welcome screen. You can see it each time you power up the unit.


The Garmin 12XL was originally released at version 2.0 (as are all Garmin units) and was a breakthrough in hardware design by offering a 12 channel receiver that would basically obsolete all of the existing multiplex units. Later, the user interface was modernized to the screen format of the current 12 models and the version was changed to 3.02. These early units used a different (slower 16 bit) processor than the newer units, consumed much more power, and were not firmware updateable by the user.

The 3.5 and later releases of this family of products marks a significant hardware change from the older G-12XL units. The battery life doubled with this hardware to 22 hours or more. Units got a new backlight with 3 levels of backlight display and many other not so visible hardware and software changes.

Note that the G12, the G12XL, and the G48 up to the 4.5 release use exactly the same software. The units automatically sense the machine to enable the appropriate features. The G12XL and G48 have all of the features of the G12 plus support for a city waypoint database and, for the G48, a buoy database. For more detailed information on the G-12XL and the G-48 see below.

I bought a 3.52 unit and then sent it to Garmin for a 4.0 upgrade within the first 60 days. I got my G12 back from Garmin with the upgrade to 4.0. I can now comment about the differences. First of all the manual is the same. No differences are documented. It would have been nice to have seen an addendum from Garmin. Mostly the G12 4.0 release is just to match the G12XL and G48 releases so the same software can be used in all of these units. There is no substantial differences from earlier G12 units. Now, on to the subtle differences.

The 3.52 G12 was upgraded to 3.53 to fix a serious problem where the unit would shut itself off when trying to process 11 or 12 satellites. This remains fixed in 4.0 as expected.

The status screen and the position screen seem the same as before. The map screen has several noticeable differences. The CFG menu item has been changed to OPT. There are many new zoom levels which you might consider an improvement or merely a nuisance when trying to scroll through all of them. The zoom is from .2 to 500. The panning feature using the cursor keys can now scroll in 8 directions instead of 4. The navigation screens are the same. (Can you customize the bottom entry in 3.52 differently for the two screens? You can in 4.0. I forgot to check the older one.) The menu screen now has a separate setup menu which means that getting to setup menus requires more keystrokes. A new alarm entry is available under setup which is why they needed more room. This alarm entry can be used to change the arrival alarms to a fixed distance instead of the automatic mode which is based on time of 1 minute or you can turn them off completely. There is also a new CDI alarm that can be turn on/off at a custom distance setting. Since the G12 has only visual alarms this may be of limited use. With all of the attention to alarms I was surprised that there was no anchor alarm but you could coerce a a combination of CDI and proximity alarms into this job perhaps.

One thing I missed on my first look was a new feature on the popup menus such as the menu that appears when you press goto. Menus like this are composed of two sections. One section lists waypoints and the other section contains a few commands. A new feature is the ability to use the left/right arrow keys to jump from the waypoint list to the command list. On the older version you would have to wade through the whole list of waypoints to get to the commands. The new behavior is present on the goto screen, the route screen, the waypoint list, and the proximity list. The up/down arrow keys work exactly as they did before. Another change was actually an old feature that returned. You can now control the baud rate of NMEA modes. (This paragrah added 8/5/98)

Hardware-wise there are no external differences. When I tried to measure the current drain I found a new power technology present. The unit looks like it is being driven with a square wave rather than direct DC. I don't know how this will affect the life of the batteries but may lengthen it a bit. The G12 is already the best unit in the Garmin camp for battery life since that city database must consume some power.

Performance-wise I can only provide subjective information. In my 2 story house I was able to track some overhead birds that I don't remember being able to track before. Perhaps it is slightly better but not appreciably so. It doesn't seem any worse at least. When I pointed the unit down I noticed a slight drop by about a pixel in signal strength which I didn't notice on the older unit so perhaps there is some sensitivity to antenna direction. Anyway these are some things to think about. Anybody find something I missed?

I used it on a motorcycle ride through the mountains with lots of trees and it tracked flawlessly. It even tracked well on my public transit train ride this morning, only losing lock once for less than a minute in downtown. This is about the same as the old unit. On a track back it seemed to find a few more bends to add in the route but I only compared one route so this too is subjective and I may have been driving the other way the first time I recorded it.

4.0.2 differences - update 12/18/98

In 4.0.2 Garmin has added the capability to interface a computer with real time update information in Garmin mode, called PVT. This means that, if the software supports it the GPS can remain in Garmin mode all of the time whether uploading and downloading track and route data or supplying realtime location data. There is also a correction the the RTCM mode which had a baud rate mismatch. There is a correction to the scale readings on the circles available on the map page. They now indicate the zoom scale for all zooms. (Some were missing in 4.0.)

4.5.1 differences (updated 1/14/99)

In 4.5.1 Garmin has added multiple language support for 9 languages. This unit has different hardware that only includes 1 level of backlight. Some machines have reported a problem with the date jumping ahead to some fixed value.

4.5.2 and 4.5.3 differences (new 1/14/99 revised 4/2/99)

The 4.52 release and 4.53 release offer the same level of functionality to the two different hardware platforms. The 4.02 version is upgraded to 4.52 while the 4.5.1 version is updated to 4.5.3. The 4.02 version gets the new multiple language support while both units add the New Zealand Grid and a fix for the date problem noted above. 4.5.2 also fixes a bug where if you had two message events associated with waypoints then only one waypoint name would get reported. This most often happened when you have a proximity alarm set and an arrival alarm in same area.

The two different hardware platforms have slight differences with the most obvious being 4.5.3 doesn't have a variable backlight.

4.5.4 differences (new 99/4/2)

4.5.4 brings the functionality of the two hardware platforms for the G-12 to the same level. This upgrade has the same number but still has different upgrade files for the two G-12's. There is only one upgrade file for G-12XL and G-48. The upgrade for the 4.5.3 adds three level backlight to the G-12. There was a bug introduced in 4.5.3 where a grid change caused the datum to switch to the New Zealand datum. This was fixed in 4.5.4.

The upgrade mainly adds TD/Loran coordinate support to the G-12 family of products. The document also notes that multiple waypoint alarms are now supported however this fix was actually part of the 4.5.2 upgrade but failed to get documented by Garmin. To use the new TD support you will need a Loran map to get the data you need to fill in the necessary fields.

At the 4.5.4 level there is still one visible difference in the two hardware configurations of the G-12. When powered by an external supply battery gauge on the new unit switches to reading the external battery voltage while the older unit turns off the gauge completely which is the same behavior found in the G-12XL and G-48.

4.5.5 differences (new 99/6/10)

The G-12 fixed one problem. One or more of the countries in the initialization screen had incorrect lat/lon position. I suspect this problem was only with one hardware version of the G-12 since there was no cooresponding fix for the 12XL. The 4.5.5 fix for the 12XL and 48 fixed a problem where the audible tone would change pitch when the baud rate on the interface was changed.

4.5.7 difference (new 00/3/7)

Enhanced battery life with a power save mode. Added the ability to calculate an area defined by the tracklog.

Power Save works by sensing whether there is significant change in activity. Significant change means speed change or direction change. In the absence of either the sample interval is reduced to 5 seconds instead of 1 second. This significantly reduces battery drain under some conditions. In addition they changed the mask angle of satellites that they will try to use so that they don't attempt to use satellites close to the horizon. This also reduces battery consumption. As to the detrimental effects it all depends on what happens. You may see none or it may cause overshoots on turns. If you are on a twisty road you just won't get the battery savings. You may see a slight difference in distances as measured on the trip meter. It is also possible that you might lose lock easier in heavy tree cover but this is just conjecture.

The second feature is an area calculator. You reset you track log. Travel around the area that you want to measure and then let the machine calculate the acreage. This is the first survey feature to make it into a navigation receiver. Units used can be changed.

4.5.8 difference (new 00/12/2)

There are three changes in 4.5.8. A fix was made when updating waypoints via NMEA WPL sentence to create a default icon. A fix was made to correct and error inthe Loran TD position format "W" and finally there was an update to the magnetic variation tables based on IGRF 2000.

4.6.0 differences (new 03/8/19)

The only difference specified for the 4.6.0 release is an update to the French language messages. There was also some products released with 4.5.9 but there was no upgrade. This generally means that there were some hardware changes that required a new version but it has no user impact.

Differences to the G-12XL and G-48 products.

The Garmin G-12 represents a great entry level product to the world of GPS. It has 12 parallel channels and shares many great features with its siblings the G-12XL and the G-48. As a matter of fact the code in all three units is the same but it customized dynamically to fit the correct model. However many people want to know what the real differences are in the other products in the family. This information is based on the latest manuals available for downloading at the Garmin site and some information I have gotten from posts to the news group. Hopefully this will help people understand whether or not to upgrade or why they might want to buy something more expensive than the Garmin G-12.

G-12XL V4.0 and above

The G-12XL looks identical to the G-12. Hardware differences include a connector on the back that can be used to power a remote antenna, a different power supply that can use external power from any source of DC from 10 volts to 32 Volts, an audible alarm, and some additional memory that contains a database of waypoints of selected cities throughout the world. As compared to the newest G-12 hardware configuration the G-12XL has three levels of backlight while the new G-12 has only one.

Software differences are mainly associated with the hardware differences. There is a menu that permits controlling the audible alarm and a new find cities screen. This screen is available from the goto menu, the option menu on the map screen, and from the main menu screen. The find cities screen looks similar to the standard waypoint screen except that you have only read access and there is a menu choice that will permit you to see the waypoint on the map screen. City waypoint data is shown on this screen and the map screen but to actually use the data for a goto or as part of a route it will need to be copied to one of the 500 user waypoints. The G-12XL provides intuitive techniques to perform this copy operation and even shortens the city name down to 6 characters for you. In addition the map option screen contains another menu item that lets you do city setup which basically lets you determine when, based on zoom scale, various cities will show up on the map screen. There are three city sizes; small, medium, and large that can be controlled separately. The largest cities cannot be turned off.

G-48 V4.0 and above

The G-48 was originally released at 4.0. Hardware differences from the G12-XL include a different color and a different antenna setup. Instead of the internal patch antenna the G-48 has a bnc connector with an external helix antenna attached. The antenna is removable and can be mounted remotely using a optional cable extension or replaced with a remote amplified antenna. It also has additional memory for a marine database.

The G-48 has three software features not found in the G-12XL. The map options menu contains a new entry to customize the display of the navigation aid (navaid) objects. The navaid objects include beacons, foghorns, buoys and are displayed on the map page as one of 10 special icons. Even the color of the buoys is shown. Navaids can be the target of gotos and participate in routes. The manual states that the navaid database can be upgraded but there is no documentation on how to do it. The second new feature is the addition of an anchor drag alarm available in the alarm menu and the third feature is a speed filter. The speed filter permits you to adjust the sensitivity of the speed updates to remove the variation caused by wave action. It can be adjusted manually or set to automatic mode.

New upgrades to the 12XL and 48 (Update added 99/1/14 revised 00/7/31)

The 12XL and 48 also received the 4.02 upgrade as described above and the new 4.52 upgrade. The 4.52 upgrade for these two units adds the foreign language support which supports a total of 9 languages and the New Zealand grid. The 4.54 upgrade add TD/Loran grid support. The 4.55 upgrade fixed a problem where changing the baud rate would change the frequency of the audible tone. The 12XL and 48 have also been upgraded to the 4.57 release and 4.58.

The new G-12CX (revised 99/4/2)

There is a new member of the G-12 family that has been released. While the name of this unit would indicate a family connection it is has significantly different hardware from the rest of the units. It has a battery life of up to 35 hours, using a battery save mode, and a new keyboard as well as a color display. The keyboard has two new keys, zoom in and zoom out. This means the map sceen has a little more room since the zoom function need not be at the top. It also has 1000 waypoints with a new tab waypoint management system and a longer tracklog of 2048 points which is twice the size of earlier units. The initial production release of this product is 2.01 which matches the 4.54 functionality of the rest of the G-12 family. This unit is not really part of the G-12 family as described above but rather a new unit.

The G-12 and 12XL version 3.62 (added 00/7/31)

I just found some really interesting news from Martin Seneclauze, an owner of a Garmin G-12 version 3.62. He had a few exchanges with Garmin related to his unit and found out that it was an intermediate release containing the new hardware but the old software. Supposedly this unit could not be upgraded but Martin was undaunted and decided to try anyway. Here is what he did in his own words:

In the garmin updater to 4.57 there are 3 firmware files:

I imagined that the last 3 digits were the new firmware version and that
the previous 4 were the old version followed by a 0 so I changed the
names of the first two (the third one was not interesting for me) to

and ran the updater. It worked (although I was worried during the
download !!!)
Thanks Martin for this great information. Perhaps it will help some other folks. No guarantee that it will work, however it did for Martin.

Dale DePriest