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GPS for ULTRALIGHTS
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(By Ed D'Antoni ed.dantoni@bbs.logicnet.com)



There are a number of inexpensive GPS units suitable for ultralight use. All GPS's provide basic ground speed, track, track to destination, distance and time to destination, course deviation, time etc. Inexpensive units do not have pre loaded databases and generally work at speeds of up to 103 mph. Last fall Canadian Tire was selling the Magellan 2000 for $275 Canadian. I obtained one for trial purposes and found it suited my ultralight needs quite well. Since I also fly conventional aircraft I decided not to buy the Magellan and started looking at what would best suit my needs. The jump up to aviation systems starts with systems typical of the Magellan Skyblazer and Garmin GPS 89 at approximately $650 CDN. These are basic systems with North American or World Data Bases. For an additional $250 you can step up to a system with databases that include control zones, airport frequencies runway details etc. Then for another 4 or 5 hundred dollars, systems that show roads, rivers and significant geog raphical features. Our original thought of a $300 purchase has now jumped to $1500. Purchasing a GPS is much like purchasing a computer. One picks everything one needs for a reasonable amount of money. The problem comes in where to stop spending money for extra speed, memory and video improvements.

After going through all of the above I decided what I needed was a dependable rugged GPS without a database. This narrowed the field to four units, the Garmin 38 and 45XL and the Magellan 2000 and 4000. The lowest US mail order prices are: Garmin 38 -$189; Garmin 45XL-$289; Magellan 2000-$179 and Magellan 4000- $250. The lowest Canadian Street prices are generally 50% above the listed US prices. Marine rather than Aviation outlets seem to have better selection, stock and prices. The Magellan 4000 operates at speeds up to 999mph, while the other 3 units are accurate to 103mph. The Magellan 4000 and Garmin 45XL have computer outputs, remote antenna/power capabilities and do sunrise sunset calculations. Only the Magellan 4000 is capable of a graphical search. The Magellan 4000 can display an area of from 1000 x 1200 feet to over 100 x 130 miles, showing all of the stored waypoints (airports in our case). Placing cross-hairs over any of these locations and hitting ENTER brings up information includ ing distance to navigate to that location. The Magellan systems have keys and switches below the display, while Garmin has them above the display. Generally, remote antennas and computer cables cost $50US each. Computer cable and software packages sell for $100US. The Garmin units have a separate battery memory backup system to ensure stored information is not lost should the system be inadvertently left on. Magellan units automatically turn off when the battery reaches a specific voltage ensuring enough power to maintain memory. Figure 1 is a list of comparative features. The figures are my interpretation from a variety of sources. Features and method of measurements between manufacturers are not always the same so comparisons are difficult and should only be considered as my opinion.

A word of warning, having a GPS available can make one complacent about navigation. Always use your GPS as an aid only. As an exercise I continually compute wind speeds by working backwards from my GPS ground speed and track. and my magnetic compass heading.

I chose the Magellan 4000, probably because I was more familiar with their systems, and the fact it operates at speeds over 103 mph., has an automatic shut off, and allows for a graphical search. 

				          GARMIN	        MAGELLAN
						
		                        G38    G45XL	       2000    4000

Moving map/Track plotter		yes	yes		yes	yes
Automatic track log			yes	yes		yes	yes
Log interval (minutes)			var	  ?		 10	 10
Variable map scaling			 no	 no		 no	yes
Graphic steering			yes	yes		yes	yes
Landmark/waypoint capacity		  ?	  ?		100	200
Landmark messages			 no	 no		 no	yes
Reversible routes			yes	yes		yes	yes
Go to Function			 	no	 no		yes	yes
Sunset/sunrise calculation	     	yes	yes		 no	yes
Lunar prediction			yes	yes		 no	yes
Nearest Landmark search			yes	yes		 no	yes
Graphical Landmark search		 no	 no		 no	yes
Parallel Receiver Channels		  1	  1               2	  2
Satellites tracked			  8       8              12      12
Satellite visibility & signal strength  yes	yes		yes	yes
Predicted expected error	         no	yes		yes	yes
Maximum ground speed (mph)		103	103		700	999
Odometer				yes	  ?		  ?	yes
Remote antenna option		         no	yes		 no	yes
Differential GPS port			 no	yes		yes	yes
Separate memory battery			yes	yes		 no	 no
Automatic shut off			 no	 no		yes 	yes 
Power consumption (milliwatts)		700	700		300	200
Operating time with 4 AA quality		 	    		  	 
  alkali  batteries (hrs.)		  4       4	         14      24
Weight with batteries (gm.)		260	260		280	280
Acquisition time   (sec.)		  ?      15	         30	 30 
   after 1 minute dropout
Initialization time with		  	
   approximate location (sec.)	         15	 15		 60     60
Initialization time, no data		450	450		250	200
Lowest Price $US US location	        189	289	        179     250

Note: This article was contributed during November of 1996. The passing of time will no doubt render some of the information contained herein obsolete. Please bear this in mind.
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Jon N. Steiger / jon@ultralighthomepage.com