Kerry.

As far as the pure GPS side of things go basically not a thing. It's what it does with what it gets that can make a difference. And what that means it comes back to functionality that "you" specifically require from it. Specific queries like this simply makes one wonder what the real underlying purpose of the post is. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Accuracy (RMS)3 after differential correction GPS Pathfinder postprocessing (4) . . . . . . . 50 cm + 1 ppm GPS Pathfinder Office carrier postprocessing With 5 minutes tracking satellites. . . . . . . 30 cm + 5 ppm With 10 minutes tracking satellites . . . . . . 20 cm + 5 ppm With 20 minutes tracking satellites . . . . . . 10 cm + 5 ppm With 45 minutes tracking satellites . . . . . . 1 cm + 5 ppm Real-time . . . . . . . . . . . . . . . . . . . Submeter(5) (3) Horizontal accuracy. Requires data to be collected with minimum of 4 satellites, maximum PDOP of 6, minimum SNR of 6, minimum elevation of 15 degrees, and reasonable multipath conditions. Ionosperic conditions, multipath signals or obstruction of the sky by buildings or heavy tree canopy may degrade precision by interfering with signal reception. (4) Postprocessing with GPS Pathfi nder Offi ce software or GPS Pathfi nder Express service. (5) RTCM SC-104 standard format broadcast from a Trimble reference station. Accuracy varies with proximity to base station. Smithy, Those are the accuracy specifications for a ProXR. You might note they are RMS accuracy figures after differential correction or post processed. Differential corrections are rather different to "averaging". One simply won't get 1 foot accuracy as a pure SPS user without some form of corrections and that excludes averaging (as such). Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Spange & Crew:.... If the data from Kerry's plots were averaged, I am curious as to how close to the true position would that number be? .... Averaging, basically a 50/50 chance for better or worse but of course depends on the length of time but many here don't have the time to average with any integrity. The thing is at the time one doesn't know if the position is better or worse. If your curious, the following highlight the actual affects of averaging http://www.cqnet.com.au/~user/aitken/gps/gps_avg.htm http://www.cqnet.com.au/~user/aitken/gps/avg_pii.htm http://www.cqnet.com.au/~user/aitken/gps/gps_obs.htm Cheers, Kerry. I never get lost everybody keeps telling me where to go

Averaging these days has limitations and time is one of them. The amount of time most are prepared to average coordinates is just about useless and in fact can actually degrade the accuracy. Certainly 12 hours will show some results and 24 hours even better but 5 or 10 minutes basically a waste of time. I'd have to agree with the 2 dogs that there is in no way shape or form a typical standalone SPS single freq (or even dual freq for that matter civil or military) receiver capable of some of the rather outrageous accuracy some "claim" from their receivers. In technical terms it simply ain't possible. Augmentation, differential and some of the other methods totally different but those that claim 1 foot from something like a ProXR isn't a standalone type receiver. An example (only a few weeks old) of 2 different receivers both measuring comparable SPS accuracy. The (red) one on the left 95% accuracy 2.8m, the (blue) one on the right 95% accuracy 3.1m. These values are ACTUAL measured accuracy figures and the accuracy "difference" is less than a foot (0.3m). The left numbers are from a $25,000 9 channel (dual freq but not that it matters in this case) and the right from a $500 garden variety 12 channel. The difference in accuracy is bugga all and considering a few other things totally irrelevent. Mind you that receiver on the left is "capable" of milliletre (even sub mm) type accuracy if "used" in certain ways but certainly not simply by itself in Standard Position Service mode just like most recreational receivers use, same system, same signals. everybody keeps telling me where to go

quote:Originally posted by Citizensmith:I typically get around 1.5 feet horizontal .... Could you explain how you achieve that. quote:What we need is a handheld unit that can download the almanac files. All GPS receivers (including handhelds) have to download an almanac, no almanac, no work. Even the most simple Garmin can download and almanac. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Actually every GPS has to download an Almanac file otherwise the thing simply wouldn't work. Again this misconception that the more satellites the better the accuarcy, not so. The DOP (and that is Dilution Of Precision) has to do with the strength of the geometry of the satellites not the total number. "1.1 to 1.5 feet" not in real time you won't, post processed you could but hindsight might be ok for hiding but not for finding. Cheers, Kerry. I never get lost everybody keeps telling me where to go

UTM might display to whole metres but doesn't necessarily mean that precision is 1 metre. Some might have noticed that trying to enter some specific last digit UTM coords that what one tries to put in is actually changed by the receiver. Basically the receiver is conforming the display compatible with the underlying coordinate system the receiver is actually storing the information in. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Not sure what it would be called over your way but a thing called "occupation", what one is/has historically actually occupied as defined by boundaries, markers, monuments even fences etc etc in most cases takes precedence over lines on paper but is generally looked at in relation to surrounding boundaries as well. There is generally a precedence based on historical and all other relevant amount of information at all levels of land entitlement. Actually land titles and boundaries are far from an exact science for a number of reasons. Cheers, Kerry. I never get lost everybody keeps telling me where to go [This message was edited by Kerry on August 14, 2003 at 03:05 PM.]

Honestly one has to appreciate the equipment and methods of the time and in all this saga this simply hasn't been understood well at all. Geez in some countries blocks were cut off based on horse traverses. Like how far can a horse walk in a period of time? If it was my block I would have wanted a long long legged horse Time to really get over this or at least understand what times and conditions were like back then and simply the way things were done, done the best way with the equipment of the time. Cheers, Kerry. I never get lost everybody keeps telling me where to go

100 feet under normal conditions maybe/maybe not. Under normal conditions that's a little more than what the system has been generally providing of late. Less than 30 feet is generally around the norm but keep in mind that the system is spec'd at less than 13m (42 feet) 95% of the time under average conditions and 36m (118 feet) 95% of the time under worst case scenario. For your location (Secane, PA) the 100 odd foot mark can also close to the difference between NAD27 & WGS84 (about 108 feet). So there might be some datum issue? Cheers, Kerry. I never get lost everybody keeps telling me where to go

Maps can be highly variable depending on the original scale or resolution that the map data was actually collected at. Many maps are still based on older methods of data collection/accuracy and actual GPS positions will certainly be better than most available maps. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Knowing what that quote:significant distance might be is the key to any meaningfull reply. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Yes I'd have to agree with that about engineers but mind you there are a few (just a few) that are the exception. Unfortuneately one has to be "nice" to engineers for several reasons but Engineer jokes? Hardest 10 years of an engineers life? First grade. Surveyor Jokes? Hardest 10 years of a surveyors life? Teaching engineers the basics of surveying. everybody keeps telling me where to go

Most countries base levels relative to sea level derived over a fairly extensive time period (around 19.5 years depending). In any case level runs, which a height datum might have been based on aren't exacly perfect either and along with many other factors there's always going to be some anomolies. With GPS the situation is complicated even further as heights derived from GPS have to be "corrected" to whatever the height datum might be as GPS heights are relative to a mathematical reference surface. Things like gravity and differences in the geoid relative to a sea level model also introduce issues. Actually some countries with the aid of long term GPS observations are now finding that in simple terms, No the sea isn't "level" (as such) as has been previosly adopted for height determination. Your father probably gave to the best generic answer as from there on it becomes rather complicated. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Peter, Have found some notes and your right the version 2.x of the 12XL was a 16 bit processor and subsequently not able to be updated. It's also interesting to note that there were no documented changes between 3.5x and 4.x, which leads some to think it was only a software alignment with other compatible models. 3.5x's were in fact updated to version 4.0x's by Garmin with no apparent changes to the hardware? So yeah the version 2.x's remain 2.x's Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by TEAM 360:My Magellan Platinum does the same thing. First it overshoots the coords .... That has all the hallmarks of auto averaging, why they don't make this a user switchable option is a laugh also, they switch/select some of the more useless features on/off but auto averaging, oh no completely stuck in their (old) ways. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Never thought I'd see a new software version for the 12/48 etc but after 5 years they release one with French translation changes? Wonders will never cease. Anyway 2.02 you've got a problem (as you realize) as you need the interim updates (there's probably several of them?) to get to and be able to update with any of the currently available updates, 3.53 - April 1998, 4.60 - Aug 2003. I suspect you might be stumped with 2.02? Cheers, Kerry. I never get lost everybody keeps telling me where to go

At that time all data was purposefully distorted. I got the impression that you thought by entering a "correct" elevation when initializing that this would somehow affect the elevation readings from that point on, BUT that is not the case. All that initial elevation input did (similar with an approx location, date & time) was help the initializing procedure. Once initialized the date/time was fixed from the sats and the position & elevation are separately computed each fix and not connected in any way to those initialize "approximate" (or otherwise) inputs. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Trees don't do GPS signals any favours and being as weak as the signal is if the signal is obstructed then it really doesn't matter what type of antenna one has. There appears at times a rather over expectation with things like trees, buildings etc. For sure there's things one can do that can "possibly" affect the "chance" of an issue. External antenna's help reduce the "chance" of a person's interference, always facing the equator with a handheld gives one the best possible "chance" to also reduce signal obstruction. Actually get out from under the tree is the best of all The problem/issue is going to be totally variable and dynamic as maybe come back to exactly the same position some time latter and there might not appear a problem then. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Nightstalker1967:If you really 'want' to enter a correct elevation value in your unit you can do it this way .... You should eventually get a decent value recorded. What GPS receiver are you referring to? Cheers, Kerry. I never get lost everybody keeps telling me where to go

No Elevation is not a user configuration except for receivers capable of being configured specifically for 2D but 2D configuration is only suitable in specific instances. Cheers, Kerry. I never get lost everybody keeps telling me where to go

One should keep in mind that there are currently several Global Positioning Systems (GPS & GLONASS) plus other currently in the development process (GALILEO etc). By default or it might just be that GLONASS has had a few political issues the NAVSTAR GPS system was basically available first so "receivers", which receive GPS signals really have been incorrectly called a GPS. There's not too many "GPS's" (as many like to call "it") that will recieve GLONASS but GLONASS is still a Global Positioning System. These are generally referred to as GPS+GLONASS receivers Cheers, Kerry. I never get lost everybody keeps telling me where to go

Clueless you may be but when you get to where ever your supposed to be going then tell them their coordinates are USELESS. Cheers, Kerry. I never get lost everybody keeps telling me where to go

It'll do what you require it to do for this purpose just like all the rest regardless of end, but if it's worth it compared to a new one with warranty etc will all depend on the price. At the right price and in working nick, no problem. Cheers, Kerry. I never get lost everybody keeps telling me where to go

2 points. If a unit looses coverage and stops navigating then it should start ringing alarm bells. There is absolutely no reason not to and quite frankly poor information if it doesn't. Auto-averaging, another userless feature, wonder when Magellan might actually make it so one can turn it off. Cheers, Kerry. I never get lost everybody keeps telling me where to go