+user13371 Posted January 20, 2009 Share Posted January 20, 2009 Background: In another thread, one user claimed amazing accuracy for his DeLorme PN-40; no more than 5' deviation from a known 7 mile track). At least one other user who insisted nothing short of a survey grade unit could be that accurate. A long debate ensued, derailing the original topic. Not wanting to further pollute that thread, I figured I'd post my non-scientific observation here: The PN-40 may be the most accurate hand-held GPS I've ever used. I can't validate another users' claims about tracking. But my tests with averaged waypoints for fixed locations show it to be much better than these devices that I have personally used: - Magellan SporTrak Pro (previously owned) - Lowrance iFinder H2O (previously owned) - Magellan eXplorist 400 (previously owned) - Garmin eTrex Legend HCx (currently own) - Garmin GPS Map 60csx (borrowed from work) I've done the same testing with every unit I've ever owned. My methodology is simple but may not fit some folks' ideas of scientific rigor. I set the GPS in one place on my property for an hour, mark a waypoint, then move somewhere else on my property (e.g., from one corner of my backyard to the other). Do the same several days in a row at different times of the day. Then I look at the saved coordinates in Google Earth. Before anyone reminds me that GE's georeferencing can be off, let me say add that: 1) GE is spot on in my location, and 2) I'm looking for the waypoints' relationships to each other as well as how they line up with the aerial photos. I'm used to seeing waypoints taken days apart to differ by 10-20 feet, and I'm happy with that. that's more than good enough to find a geocache, or something really important like a good cafe. Fact is, under most conditions all of the above named GPSRs were pretty close to each other. But the PN-40 has consistently been LESS than 10' off for waypoints set on different days, times, and sky conditions. And they cluster right around the real locations; the ones at the outer range of error are rare. In several sets the errors were small enough that under maximum zoon in GE it was hard to measure. The kicker: All waypoints in the above test were set on the PN-40 with WAAS disabled. Quote Link to comment
+Hrethgir Posted January 20, 2009 Share Posted January 20, 2009 I was really happy with the accuracy of my PN-20 when I had that, and from what people are saying, the -40 is even better, so that makes me happy! Haven't gotten out with my -40 yet, but will very soon. One thing I can say is that my -20 never found a single satelite from my living room sofa (right by a window), while the -40 is able to see enough to get a 3-D fix with a not-too-bad +/- error, so that bodes very well for performance under tree coverage. I know there where a couple places at Disneyland where the -20 track went yellow, but my Legend HXc was able to keep a solid lock. Oh, and the Legend locks on pretty well from my sofa, and even from the middle downstairs hallway of my 2-level apartment, it's really pretty amazing! Just stay away from water, though, it looses it's mind there. Tried setting a waypoint on a dock in a river, and with the Legend, I tried twice, and both points were out in the water, and in opposite directions from each other, but the point I set with the -20 was spot-on. Quote Link to comment
+Vertigo Posted January 21, 2009 Share Posted January 21, 2009 One thing that I have noticed with the PN40 that I really love is that it doesn't waiver, it picks a spot and pretty much sticks with it. Granted I only have an old GPS V and LEgend to compare with, and they would be all over the place, moving around quite a bit. The PN-40 picks a spot and pretty much commits to it. This is an attribute of accuracy. I can't wait to see what it will do with a WAAS connection. which I have yet to see. Quote Link to comment
+Team CowboyPapa Posted January 21, 2009 Share Posted January 21, 2009 Thank you, Lee! Very refreshing to see an unbiased, hands-on comparison based on actual, controlled testing. Quote Link to comment
+Klemmer Posted January 21, 2009 Share Posted January 21, 2009 I've now had my PN-40 to the same benchmark on two different days (adjusted Triangulation Station - absolute accuracy within less than one inch). I also had my Magellan Meridian Platinum (with new WAAS firmware fix) with me both times. Both had good WAAS reception & corrections. After about 3 or 4 minutes averaging: PN-40: 3 or 4 feet Maggy: 10 to 12 feet Unscientific, yes. Both are really OK, actually better than the GPS system "specification". Both units held to best benefit of their respective antenna types. Nice to see the newer technology do better. I would guess that any recent technology unit would do about as well as the PN-40. A lot may just be luck sometimes. Quote Link to comment
+user13371 Posted January 21, 2009 Author Share Posted January 21, 2009 (edited) Thank you, Lee! Very refreshing to see an unbiased, hands-on comparison based on actual, controlled testing. You're welcome. The main point of my first note was to say how impressed I am with its accuracy in static testing. I haven't tested it for tracking yet. And I didn't outline the PROBLEMS with the PN-40, 'cuz I didn't want to set off the rabid fanatics. Are any of them around right now, or is it safe? To be completely unbiased, I'd have to also point out some of what I see as negatives: - It eats batteries. A good set of rechargeables is a must and any extended field use -- even a couple days of hiking or bicycling -- means carrying lots of spares and stopping to swap batteries often. - It's bulky/heavy compared to something like an Explorist 210/400 or an Etrex series. Some people won't mind, but cyclists tend to be weight weenies and I imagine some hikers are also. Add room in your pack for the aforementioned spare batteries, too. - No real support for non-Windows OS at this time, beyond "pre-cut" maps on CD that you can load to the SD card. Interoperability with other software is immature compared to Garmin, Magellan, or even Lowrance. There's no way yet to get waypoints & tracks in or out of the device without using Topo 7 or XMap running under some version of Windows. - The quality of the maps are a mixed blessing. Because every zoom level is a bitmap, the displays are beautiful; but the files are bloody huge. I can fit a nicely detailed roadmap of the entire US on a 2GB card in my Garmin, with plenty of room to spare. The same amount of storage in the PN-40 will hold beautiful road maps plus topo data - but just for Oregon, Washington, and maybe a sliver of Idaho. Now, these things will not seem to be disadvantages to a lot of people. Some folks have bigger hands and pockets than me, don't mind carrying lots of batteries on bike rides or hikes, and memory cards get more spacious and cheaper every day. And who the heck uses a Mac, anyhow? But I'm a firm believer in "the right tool for the job." For now, the iPhone is my EDC device (location aware, good enough for urban commuting, lots of other functionality). The eTrex Legend Hcx goes on the handlebars (precise enough for road trips, economical on batteries, small and light). The PN-40... well... If I were a more active geocacher (or surveyor, or cartographer, etc), I can see how the PN-40 would be a must-have. But since I'm only a gadget geek, it's just a curiosity, an object for study. A really cool one though, gotta admit that... Edited January 21, 2009 by lee_rimar Quote Link to comment
+Team CowboyPapa Posted January 21, 2009 Share Posted January 21, 2009 Thank you, Lee! Very refreshing to see an unbiased, hands-on comparison based on actual, controlled testing. You're welcome. - It eats batteries. A good set of rechargeables is a must and any extended field use -- even a couple days of hiking or bicycling -- means carrying lots of spares and stopping to swap batteries often. Now, these things will not seem to be disadvantages to a lot of people. Some folks have bigger hands and pockets than me, don't mind carrying lots of batteries on bike rides or hikes, and memory cards get more spacious and cheaper every day. And who the heck uses a Mac, anyhow? But I'm a firm believer in "the right tool for the job." Exactly, and when we're 6 hours on a 4WD trail, averaging 5mph, to Kelly Point, I've got plenty of time to keep the Li-Ion charged from the 12VDC. Batteries, not to worry. It's the gas station 100 miles away that worries me. Quote Link to comment
+Blind Avocado Posted January 21, 2009 Share Posted January 21, 2009 I may have issues with the unwieldy Topo 7 software, but after taking the PN-40 caching several times I can't complain on its accuracy. It has been consistently spot-on, better then my 60Cx. Good review, thanks! Quote Link to comment
+user13371 Posted January 21, 2009 Author Share Posted January 21, 2009 ...when we're 6 hours on a 4WD trail... I've got plenty of time to keep the Li-Ion charged from the 12VDC. Batteries, not to worry. It's the gas station 100 miles away that worries me.Yes, everyone has different needs and different worries. When I'm cycling, I don't have 12VDC to charge the GPS. And in a pack barely big enough for a toolkit and some Clif Bars, I'm not happy about carrying even one extra sets of batteries. Clif Bars or batteries, my fuel or the electronics, hmm? So I ride with the Garmin Legend Hcx - which will run for DAYS (not hours) on one pair of Eveready e2 Ultimate lithium cells. Still, a hub driven dynamo feeding a small battery pack, with regulated output of 5VDC at a maximum draw of 1 amp -- that would solve the problem if it didn't weigh too much. Either GPS could run off of that. But that's a different topic and belongs in a different technology forum. Quote Link to comment
+user13371 Posted January 21, 2009 Author Share Posted January 21, 2009 ... the unwieldy Topo 7 software ..."Unwieldy" isn't a problem, we're geeks here! Okay, maybe unwieldy IS the right word. The big problem for me is that it only runs under Windows. Got a newer Mac? It'll run under VMWare Fusion, but not Crossover. Will probably run in Boot Camp and Parallels, though I haven't tried them. Unwieldy, okay, but not impossible... I mean, it's not a problem if you don't mind allocating enough space on your hard drive for a whole 'nuther OS on your hard drive, and taking the time to boot it up -- to run ONE application -- in a world where everything else you do is seamlessly cross platform Quote Link to comment
+fizzymagic Posted January 22, 2009 Share Posted January 22, 2009 "Unwieldy" isn't a problem, we're geeks here!Being a geek doesn't help when you have to select and move waypoints one at a time between layers... But you do have a point. I have already written a few perl tools that help overcome some of TOPO's deficiencies. But about accuracy: I have the distinct feeling that my unit is actually using WAAS data a lot more often than it is telling me, because it is so stable and repeatable. I just wish the EPE were more in line with what I am seeing... Quote Link to comment
+user13371 Posted January 22, 2009 Author Share Posted January 22, 2009 ... about accuracy: I have the distinct feeling that my unit is actually using WAAS data a lot more often than it is telling me, because it is so stable and repeatable....I've wondered about that myself. Seems to good to be true, doesn't it? I've explicitly turned it off in the device setup menu and it doesn't show #135 on the satellite screen, so I have to believe it's ignoring WAAS data. But if the GPS is already this good, is that really a problem? I guess vertical resolution could be improved a little Quote Link to comment
+Oreb Posted January 22, 2009 Share Posted January 22, 2009 Your mention of tools caught my ear. I've just ordered a PN-40 which is on its way. I was trying to decide between a 60 csx or the PN-40 and ended up going for the PN-40 despite some concerns about it being able to get and maintain a lock and how I'm going to have to change my existing GSAK>GPSr process to work with Topo and the PN-40. If you have tools that help manage waypoints I'd be interested in hearing more if you're willing to share more information. Thanks! "Unwieldy" isn't a problem, we're geeks here!Being a geek doesn't help when you have to select and move waypoints one at a time between layers... But you do have a point. I have already written a few perl tools that help overcome some of TOPO's deficiencies. But about accuracy: I have the distinct feeling that my unit is actually using WAAS data a lot more often than it is telling me, because it is so stable and repeatable. I just wish the EPE were more in line with what I am seeing... Quote Link to comment
+Ramblin Ramsey's Posted January 22, 2009 Share Posted January 22, 2009 Your mention of tools caught my ear. I've just ordered a PN-40 which is on its way. I was trying to decide between a 60 csx or the PN-40 and ended up going for the PN-40 despite some concerns about it being able to get and maintain a lock and how I'm going to have to change my existing GSAK>GPSr process to work with Topo and the PN-40. If you have tools that help manage waypoints I'd be interested in hearing more if you're willing to share more information. Thanks! You won't need any more tools, and you can continue to use GSAK but don't really need it. When using GSAK just export to gpx, then import into Topo 7. or just drag your unzipped pocket query into Topo. With the 40 hooked up and turned on, use the exchange dialog to transfer the waypoints to the 40. Quote Link to comment
+TotemLake Posted January 22, 2009 Share Posted January 22, 2009 With Topo7 and the PN-40, the only real reason I'm using GSAK now is to filter for a specific location of my choosing when I'm planning hikes. This way my PQ selection doesn't change and I don't have to worry about delayed deliveries. I just plug in a Search criteria for a specific set of coordinates and radius, then I upload the resulting GPX to T7 to see if there is something to chase in the area of interest. Where GSAK was almost a necessary third party tool to manipulate the data for my MeriPlat, the PN-40/T7 combo makes GSAK almost not necessary. Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.