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Boat Forum / Cruising / February 2005Utility of an old but mint condition GPS?
Like many YCs, we have a locker where old gear goes to die after being banished from boats in favour of the latest and greatest hardware. Members are invited to scavenge, and I've scored lots of decent gear. Today I found a small satchel containing a Trimble Flightmate PRO GPS unit (circa 1993) complete with "windshield antenna", a bunch of good-looking power cords and connectors, a spiffy case, all docs and a lithium battery pack for (I am guessing) keeping some sort of memory active, like a lithium button battery on a motherboard keeps a CMOS alive. Did I mention the extremely well-built mounting bracket? That and the 12 V lighter socket cord will come it very handy, if nothing else does. Well, I threw 4 AAs in the unit, figuring "nothing ventured", and it fired up promptly. Its screen is strictly alpha-numeric, and seem oriented to avionics, which is fine with me. Whatever it held in memory is long-gone, but I left it outside for half-an-hour and it acquired six satellites and now has an "almanac" of them, probably meaning the next fire-up won't take so long to acquire. Like every GPS I've ever used, it eats batteries, although this could be because its -3 C today and I left it in the backyard to mull things over for 30 minutes. Now it's working fine. My little tale ends with this query...should I use this in my boat? It looks professional and solid, if big and somewhat "user-unfriendly" in operation, but it's got "bigger characters" than most handhelds. On the other hand, it has about the same feature-set as my two Magellans, circa 1999 and 2001, but it does have an external antenna I can mount on a hatch and probably do faster acquires. I suspect the thick instruction manual will tell me more. I do have doubt that it could cope with the slow speeds of sailing, but I rarely need more than lat/lon co-ords.. Does anyone (including pilots who sail) have any comments? The unit looks mint, and unlike the crappy plastic mounts I have for the Magellans, I thought this baby would make a great nav station unit, because of its very solid mounting bracket. I don't require it to interface with anything, but it appears to have a stock nine-pin serial connector, so I guess I could connect it to an old laptop if its NMEA 183. Do I have a winner? R. I had a Magellan 5000 which was spiffy in its day (1994?) but became obsolete when I received a chart plotter as a birthday present a few years later. I gave it to friend, assuming that he would keep it stashed as a backup for the newer unit he had wired to his computer. It turned out he loved the Magellan in the cockpit because it had numeric buttons which allowed him to punch in Lat/Lon quickly. I'd say you probably scored a nice unit, especially if you're looking for a backup. > Like many YCs, we have a locker where old gear goes to die after being > banished from boats in favour of the latest and greatest hardware. [quoted text clipped - 43 lines] > > R. >I'd say you probably scored a nice unit, especially if you're looking >for a backup. You should see this thing. It resembles a price check scanner from a supermarket, or the larger sort of PIN number consoles for a debit card terminal. But it looks great, and you can believe from the aluminum, rubber coated mounts that it was meant to be clamped to a Cessna's steering yoke. It figured out my height above sea level at home, which is 60 feet higher than the "lake front datum" I inputed of 240 or so feet, and self corrected. It has XTE and ETE and ETA and gives me five characters to name waypoints, not three. It also has location-specific sunrise and sunset times (which a lot of units have) and azimuth angles (which they don't). Plus if I want to sail to any of several hundred airports, I'm good to go. <G> So, yeah, I can easily see this in my nav station. >>I'd say you probably scored a nice unit, especially if you're looking >>for a backup. [quoted text clipped - 16 lines] > > So, yeah, I can easily see this in my nav station. Trimble has always had a reputation for very high end GPS units. Its probably very solidly put together but may not stand up to a moist environment. You might consider offering it on eBay for $200 and see if anyone bites. Magellan had units set up for aircraft use and these are still selling well on eBay. You could then buy a marine unit with WAAS capability for not much more. >Trimble has always had a reputation for very high end GPS units. Its >probably very solidly put together but may not stand up to a moist >environment. I'm on fresh water and this would be mounted inside on the nav station. But your comments are noted...and thanks. You might consider offering it on eBay for $200 and see if >anyone bites. Magellan had units set up for aircraft use and these are >still selling well on eBay. You could then buy a marine unit with WAAS >capability for not much more. Hmm...there's a thought. Or maybe to be completely paradoxical, I could put it toward my "sextant fund". Thanks. I'd never heard of Trimble, and although they are still in business making GPS and location-finding equipment, they seem focused on surveying and such, not recreational GPS...probably the margin was too skinny. R. there was a general 'roll-over' for GPS receivers just after Y2K that required sofware / e-prom, etc. changes to keep them 100% compatible with the international system. You should ckeck to see if this was done (or not) on this unit. If not then the unit would not be totally realiable with the worldwide system upgrade. > Like many YCs, we have a locker where old gear goes to die after being > banished from boats in favour of the latest and greatest hardware. [quoted text clipped - 43 lines] > > R. >there was a general 'roll-over' for GPS receivers just after Y2K that >required sofware / e-prom, etc. changes to keep them 100% compatible >with the international system. You should ckeck to see if this was >done (or not) on this unit. If not then the unit would not be totally >realiable with the worldwide system upgrade. ===================================== That's true but for me the real issue would be lack of WAAS capability. WAAS has increased average accuracy of GPS positions from +/- 100 yards down to about 15 yards. That is a REALLY significant improvement, and is now frequently more accurate than the charts. If you doubt the significance, take a look at the number of channels and inlets that are less than 200 yards wide, or take a close look at your visible range in heavy fog or rain. >>there was a general 'roll-over' for GPS receivers just after Y2K that >>required sofware / e-prom, etc. changes to keep them 100% compatible >>with the international system. You should ckeck to see if this was >>done (or not) on this unit. There was the 1024-week rollover of GPS time which happened in August of 1999. But the unit in question locked onto satellites and apparently came up with the correct position and date/time, in which case it handled the roll-over correctly. >> If not then the unit would not be totally >>realiable with the worldwide system upgrade. If it gave correct position and date/time when it locked on then the rollover was handled correctly and there shouldn't be any concern about that issue. > That's true but for me the real issue would be lack of WAAS > capability. WAAS has increased average accuracy of GPS positions from > +/- 100 yards down to about 15 yards. No, accuracy had already improved from a nominal 100m to 15m when Selective Availability was turned off in May, 2000. Actual measurements have shown the 95% accuracy to be closer to 7m without WAAS capability. WAAS further improved the 95% accuracy in areas that are covered to about 3m. > That is a REALLY significant > improvement, and is now frequently more accurate than the charts. Even without WAAS the accuracy is frequently better than that of the charts, so WAAS is mainly of benefit when going back to a place where you've already taken (or been given) GPS positions. > If > you doubt the significance, take a look at the number of channels and > inlets that are less than 200 yards wide, or take a close look at your > visible range in heavy fog or rain. My perceptions of WAAS, turned off selective availability, etc. is that you in many cases are still using and co-relating to charts that were constructed using hand thrown lead lines and surveying instruments (sometimes on a pitching deck). Especially when using vector charts the magnification possible with such charts completely overwhelms the 'resolution' accuracy .... and can very quickly put yourself firmly onto a reef, rock, or channel berm. Jeeze, most of the coastal charts used in the USA are based on the NAD27/29 data (many of which were simply transcibed from pre-colonial charts .... and were NOT verified by 'modern' means). Running an unfamiliar channel, close approach to a hazzard, etc. by the sole means of GPS (even with WAAS etc.) is GOING to 'catch you'. >My perceptions of WAAS, turned off selective availability, etc. is >that you in many cases are still using and co-relating to charts that [quoted text clipped - 9 lines] >Running an unfamiliar channel, close approach to a hazzard, etc. by the >sole means of GPS (even with WAAS etc.) is GOING to 'catch you'. Charts in areas of heavy commercial use, like NY, Boston, and Portland harbors are mch more recent, and waas is really good. Jonesport is more like prerevolution Admiralty charts. However, the locations of Nav Aids are checked by DGPS every time they are serviced. NAD 27/29 is not common in the Northeast. Rodney Myrvaagnes NYC J36 Gjo/a "Wanting to meet a writer because you like his work is like wanting to meet a duck because you like pate." Margaret Atwood |
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