Review of the Garmin GPS-II PLUS GPS Receiver by Joe Mehaffey and Jack Yeazel Revision 3, 9/14/97 We recently received a new Garmin GPS-II Plus (G-II+) and Jack and I have been comparing it to our GPS-12XL. The units are similar but have differences which will be important to users. First, a review of G-II+ features and operation. Most of the features are the same as the Garmin 12XL unit but we will high- light the differences. Like the G-12XL, the G-II+ locks on to the SV signals quickly. From a "cold" start, after a 1000 mile UPS trip, it locked on in 50 seconds. After a 3 hour off time, the lock up time was 39 seconds. After being off a few minutes (warm start), the G-II+ would routinely lock in 10 seconds. Specifications are "warm start" , 15 seconds, "cold start" 45 seconds, "autolocate" 5 minutes. This is significantly faster than any of the single or dual channel scanning type receivers such as the G-45XL and the M-4000XL. If the G-II+ is shielded from SVs (and thus unable to lock) for a time, the unit will request initialization. With Garmin's "Initialize by Country or State" feature, you do not need your approximate lon/lat to speed up the initial lock when you move more than 300 miles with the unit off. The G-II+'s specification for position accuracy is 100 meters with SA, 15 meters exclusive of SA and 5 meters with suitable DGPS correction signals same as the G-12. This specification is considerably better than the DGPS specs available with the Eagle Explorer and most low cost single and dual channel multiplexing systems. The DGPS error specification for the G-45XL for instance is 10 meters. For the EE it is 22 meters. **The waypoint averaging mode available in the G-12XL was not present in early versions of the G-II+. Starting with firmware version 2.04, waypoint averaging is included. In any case, the G-II+ like the G-12 (and others) use an over determined solution when more than 4 SVs are locked. This produces somewhat higher accuracy than units which use only the best four SVs. Another added feature in later G-II+ versions is a feature on the "sunset" page which allows you to readout the distance between two waypoints. The G-II+ operates from 4 AA batteries or from external power in the range of 10 to 32 volts DC. External current draw at 12 volts input on my unit is about 50ma (light off). Battery drain is about 90ma (light off). Twenty four hours is specified as the AA battery life with DuraCell or similar batteries. This is the best battery life we know of in a 12 channel GPS receiver. The lowered system current drain had no apparent effect on RF sensitivity or display speed as compared with the G-12. The data/power cable used is the same as the Garmin G-45 units. The external antenna connector, a BNC coax jack, is located on the right-rear of the unit just behind the keys. The BNC jack is powered, but the standard antenna is passive. We measured 5.80 volts on the connector with battery voltage measuring 6.55vdc on the G-II+'s test screen. The Garmin GA-26 amplified antenna and the MAGELLAN M-4000 amplified antenna both work with the G-II+. We believe most other amplified GPS antennas will work as well. The G-II+ puts out only the NMEA protocol NMEA-0183 ver 2.0. Other proprietary (GARM/GARM) sentences are input/output as well. There is STILL no way to switch from NMEA to up/download without manual intervention. DGPS signals in the RTCM-104 format are accepted. A setup screen permits selection of the I/O combina- tion needed by a particular application. Operating temperature range is specifies as -15C to +70C. Unique in its class, the G-II+ and the G-12XL are rated submersible to one meter per IEC529 IPX(7). The maximum altitude rating is 60,000ft and speed maximum is 999 knots. The G-II+ has a number of features and displays that are useful. These include: (Note: &= Feature essentially identical in the G-12xl. #= New (or significantly modified) Feature vs G-12XL.) #a) A tape style compass display screen showing direction of travel, track bearing, speed, altitude (*), trip distance (*), lon/lat position, and time of day. Note: (*) display items may be interchanged with any of the following on the G-II+ (only)> Trip Odometer, Trip Timer, Elapsed Time, Average Speed, Maximum Speed, and Altitude. You must set in the time offset from UTC manually. #b) A compass rose display screen shows direction of travel and has an arrow pointing to the next waypoint. This screen also provides the name of the next waypoint, the bearing, distance, along track speed, speed, and cross track error(*) with reference to the next waypoint. On the G-II+ (only), the cross track error can be interchanged with velocity made good, estimated time enroute, estimated time of arrival, course to steer, and TRN (direction to turn to go directly to destination). This display can be alternated with two pushes of the "enter" button with the highway display below. &c) A highway page type display screen shows off track distance similar to a CDI display. The CDI scale is adjustable (Nav Setup menu) in units of .25, 1.25, and 5.0 sm, nm, or km. This screen includes bearing, distance, track over ground, speed over ground, and cross track error (*), all with reference to the next waypoint. The name of the next waypoint is also displayed. If you get too far off course, a message is presented telling you the proper course to steer to get back on course. Note: On the G-II+ (only), cross track error may be interchanged with VMG, ETE, ETA, CTS, and TRN as in b). &d) A moving map display is provided to plot your course over ground. In addition, bearing, distance, track over ground, and speed over ground are provided on this same display. Waypoints saved in the machine are displayed on the moving map page as they come within range of the map scale selected. Note. The "map" is a blank page until you put in your waypoints. This screen has pan and zoom and scales from .2 mile to 320 (miles or other units) which works quite intuitively. You can "point" at a waypoint with the cursor, and the distance and bearing to that waypoint from your present position will be displayed. You can also "mark" and store a new waypoint by moving the cursor to the desired position on the map and pressing the MARK key plus ENTER. The map may be north up, or current track up, or direction of current route segment up. The map display can contain position range rings, plot straight lines between waypoints, display "nearest" nine waypoints, or put names beside waypoints. The map screen also supports zoom and pan features. On the G-II+ (only), waypoints can have one of 16 symbols such as boat, house, etc. &e) A distance and sun screen is provided to compute the dis- tance between any two waypoints and to display sunrise and sunset information for your locality. &f) A simulator feature provides display of simulated motion and simultaneously outputs simulated tracking data to your computer for test of mapping software, data gathering simulations and such. &g) A screen back lighting timer permits setting the backlight to None, 15, 60, 120, and 240 seconds when the unit is on battery power. The screen will stay on continuously if external power is connected and the backlighting is turned on. Backlighting is adjustable in three steps on the G-II+ (only). The backlighting is uniform and tinted blue and the display at night is easy to read. The display is clear and appears to be the same display as on the G-12XL. #h) There is no audiable warning tone on the G-II+. (G-12XL has warning beep tone.) &i) A message screen page allows you to view system warnings and messages. These include such things as approaching way- point, no DGPS position, poor gps coverage, and battery is low. The total number of such advisory messages is twenty six. &j) A satellite status page comes up when you first turn the unit on. It displays a "fuel" or battery gauge showing battery remaining, and a "compass" display of satellite numbers (1>32) in view along with signal strength bars for each satellite potentially in view (up to 12). If the unit is powered from an external source, the "fuel" gauge bar disappears. The signal strength bars are hollow if the GPS has found the SV and is not yet locked and changes to solid black when lock is made to each satellite in turn. Each signal strength bar is marked with the associated satellite number. On the polar plot, SV numbers are white on black when not locked black on white when locked. #k) Waypoints may be named with a six character name plus (G-II+ only) a symbol (boat, gas pump, house, etc.) may be se- lected from a library of 16 symbols. &l) A track log is provided which can log from 0 to 999 points. If 999 points are selected, the track log actually records 1024 points and 1024 points are also referenced during download on the G-II+'s screen. After the maximum selected number of track log points is recorded, the G-II+ discards the oldest log points as new are added. The user can select "automatic" track log which logs whenever direction changes. (This turns out to be an EXCELLENT feature and provides accurate tracks over long distances with the provided 1024 trackpoints.) Alternately, track points may be logged on a selected time interval. Track Log modes available are WRAP, FILL, and OFF. In FILL, the log stops when full. &m) TrackBack is a feature shared with the G-12XL. If a user goes out along a random track and then wants to return to his point of origin, he may select, TRACKBACK, and the G- II+ will compute up to 30 "best" waypoints for a return path and store them as Route 0. When TRACKBACK is activated, the unit will route using the computed information in Route 0. (Push GoTo to access.) &n) The G-II+ accepts the RTCM-104 version 2.0 DGPS correction format. The GPS can control the frequency of suitably equipped DGPS receivers when it is set to the RTCM/NONE mode (No NMEA data output.). DGPS beacon frequency and signal strength will display on the G-II+ when DGPS activity is present on the RTCM input. Note: The NMEA I/O baud rate is ALWAYS 4800 baud on the G-II+ EXCEPT that in RTCM-104 only mode, (no NMEA), 9600, 4800, 2400, 1200, 600, and 300 baud are selectable. This could be a problem for simultaneous DGPS/NMEA operation since some DGPS receivers will not output at 4800 baud, which is the only speed you can get with RTCM/NMEA. Garmin says that all of Garmin's DGPS ready GPS receivers are compatible with all DGPS receivers which output RTCM SC104 data streams within the above limitation. Alert messages (but no beeps on the G-II+) alarm DGPS signal failure when that mode is enabled. #o) External I/O signal modes available are: NMEA/NMEA, NONE/NMEA, NONE/NONE, RTCM/NMEA, GRMN/GRMN, and RTCM/NONE. If NMEA is one of the selections, the baud rate is automatically 4800 baud. #p) No Waypoint Proximity Alarm feature is provided on the G-II+ (as is present on the G-12XL) as the G-II+ has no alarm beeper. &q) The user may select a Magnetic heading reference or true north or User Selectable reference as required. &r) The GG-II+ has 107 built in map datums plus the capability for users to set in their own datum settings. (Manual only lists 103.) &s) The user may enter his own grid format if desired. &t) If the ENTER key is pressed and held when the unit is turned ON, an undocumented test screen is activated which inciden- tally measures battery voltage. &v) The G-II+ provides 500 user waypoints. These waypoints may be organized into twenty ROUTES with 30 waypoints each. When navigating a ROUTE, as each waypoint is passed, the G-II+ automatically switches to the next waypoint in the route list. Routes may be inverted to return along a path in the reverse direction. A route may be copied to an new route number. If you select a route when your location is somewhere in the middle, the nearest waypoint will be selected as the starting point of the route. If you are on a route and do a GoTo, the G-II+ will take you to the GoTo waypoint and then resume navigating along an active route. #w) The G-II+ has dedicated ZOOM in/out buttons on the front panel. This permits easy expansion or contraction of the map display with a single keystroke. #x) The G-II+ offers a waypoint symbol feature for pictorially identifying waypoints. This feature permits the user to show such objects as anchors, boats, gas pumps, houses, cars, fish, etc. (sixteen different icons) to further identify waypoints on the map display. #y) A "Delete By Symbol" feature permits deleting all waypoints of a class. G-12XL users will be interested to know that TrackBack waypoints may be deleted in the G-II+ as a "class". &z) The G-II+ offers the unique ability (like the G-II) of being able to operate its display in the horizontal or vertical format. This is convenient for automobile dash operation. Subjective Observations of Performance Jack Yeazel and I have been out testing the G-II+ on the road and in the field. The G-II+ has worked without a flaw that either of us could find. We uploaded and downloaded waypoints, tracks and routes using Waypoint+(W95), and G7to..(DOS). We tried it out on SA4, Delorme MapExpert 2, Precision Mapping 3, Vista, AutoRoute 5, and MetroGuide 2. No problems found. (Some upload/download programs may require the later releases.) We compared it with the G-12XL. The G-II+ performed on a par with the G-12XL and the EE in every test for lock stability, multipath performance, re-lock after an underpass, and ability to suddenly change direction without loss of lock. As with the G-12XL and the EE, we were very impressed at the speed that the speed the G-II+ responded to changes in direction. At about 4mph, the G-II+ would complete a change of direction in about 15 feet. Previously we found with the G-45 about 50ft, and the M- 4000, about 60ft. The G-II+ laid down smooth tracks on our highway maps during all tests. No gaps, jumps, etc., (The G- II+ has data smoothing like the G-12xl.) Performance under tree cover was about the same as the G-12XL and the EE and we rate that as very good. We noted that the G-II+ was considerably less sensitive to interference from the Eagle Explorer than is the G-12XL. However, all three units show reduced sensitivity when placed within a few feet of Jack's cellular telephone. We found the display controls easy to learn and use. The dis- plays and controls are (mostly) well organized and logically arranged. We find the G-II+ and the G-12xl controls and display system somewhat easier to learn and use as compared with the Eagle Explorer. These are the major features We have observed in playing with the G-II+. Our impressions are that the G-II+ is pretty similar to the G-12XL in features and performance. The G-II+ has a few features not present in the G-12XL and vice versa. A potential purchaser should carefully review the differences and be sure a needed feature is present in his selection. We made these tests using a Toshiba 2150CDT laptop computer run- ning moving map software. The two gps units were operated on the dash in front of the driver (G-II+) and with the G-12XL on the dash in front of the passenger. The laptop with Moving Map Software were used to log tracks, "cookie trails", and opera- tion for comparison. Since the G-12XL and the G-II+ use the same receiver and exhibit- ed essentially identical tracking performance in our tests, we did not perform the extensive field trials we made with the G- 12XL, EE, and others. For more information on tracking results with our testing of the G-12XL, see the following URL. http://www.bridge.de/~tom/garmin.htm We noted that both the G-12XL and the G-II+ have a form of "dead reckoning" for moments when signal dropouts occur. For instance, if the G-II+ is tracking along and just before a sharp turn you invert it and block its antenna, it will continue to track straight for about 30 seconds. It also provides a very good data smoothing filter to throw out random fixes that are way off track. This results in an exceptionally smooth track on a moving map display even when multipath is present. Even with this filter, there was no overshoot apparent during quick stops, sharp turns, and similar maneuvers when normal continuous track- ing was taking place. If anyone has any additions, questions, suggestions, error corrections other comments, please feel free to Email Jack or Joe. Joe Mehaffey and Jack Yeazel