Kerry.

Just hope any further decisions don't take as long to decide as the actual decision to procede. A good motto for GALILEO might be "Better late than never" but what wasn't mentioned in any of those releases was the extra accuracy comes at a price as much of GALILEO's services will be subscription type services. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Noise in GPS terms is atmospheric type of noise and simply not noise noise. Noise is actually useful for certain systems that make use of GPS. Cheers, Kerry. I never get lost everybody keeps telling me where to go

THe following are actual EPE numbers verses actual accuracy. 3 different models, all the same brand but range over the years since 1994 and have software versions that reflect their era. The data is based over 23 hours and the oldest one (pre SA software version) was done twice for confirmation. All are straight stock standard GPS positions (no augmentation) Day 1, Model X (as current as one could get) EPE average 4.16m, range 3.3 to 6.5m Actual accuracy @50% 1.7m (max 5.4m) Day 2, Model Y (superceded model but post SA software) EPE average 3.56m, range 2.8m to 6.4m Actual accuracy @50% 1.7m (max 7.6m) Day 3, Model Z (superceded model pre SA software) EPE average 11.4m, range 8.9m to 101.3m Actual accuracy @50% 3.1m (max 19.0m) Day 4, Model Z EPE average 11.4m, range 8.7m to 95.5m Actual accuracy @50% 3.1m (max 18.1m) One can ponder what those numbers actually mean but for what it's worth, my thoughts: There really is bugga all difference in the actual accuracy (in practical terms) and certainly well below the system spec. Model Z only outputs to 3 significant decimals (the 2 other units capable of 4) so around 3 metres is probably the best it's going to do anyway. The EPE for Model Z (pre SA software version) doesn't even come close to the current real world accuracy and follows the thinking that EPE is rather a fudge figure and doesn't follow any set rules. It's also interesting that the maximum EPE for Model A (Day1) was greater then the maximum actual accuracy. Not by a great lot but all the same why should the EPE exceed the "actual" error? Based on Model X & Y the EPE basically sticks to the (average) middle ground generally ignoring the low & high accuracy numbers. Cheers, Kerry. I never get lost everybody keeps telling me where to go

CR, I would imagine this 2 mile radius range has to do with radio freq range limitations, which if it is, is really a different issue to the GPS side of things? unless of course the Rino is only approximating things, which then really doesn't follow the principles of differential. Cheers, Kerry. I never get lost everybody keeps telling me where to go

are these two people twins, are these 2 units "identical", same software version, same everything. I relaize it might all sound simple but it's probably not. The wavelength of L1 is about 20cm so in theory/practice if 2 receivers were a foot apart there could be entirely different conditions affecting receiver variables, which that receiever might be relying on to calc values. Differential works on ranges/shifts to individual satellites and isn't based on a coordinate block shift. In all the reasoning, there's probably that 50/50 reasoning. Half the time it might be better the the other half it won't. The thing is one still won't be able to tell which half it is. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Geo-Actuary:Hi Kerry, Using that line of reasoning, each GPS unit made by each manufacturer would produce results, not only in the accuracy measurement, but in the basic measurement of Lat/Lon and all other readings, that would not be at all compatible with other units. But, ... we all share waypoints that we record and we all are able to find them using different GPS units. If someone records a location and has an accuracy of 30' and you locate their waypoint with an accuracy of 30', you could easily be standing right on top of it or you could be 60' away from it. All I'm suggesting is that the unit's ability to estimate accuracy is reasonable, no matter which unit it is, since they all use the same satellite readings and the same level of mathematics to determine distance and timing information. See my response to 'Searching-ut' for another view of the use of the accuracy field. Mike Mike, as many of the others have mentioned EPE is one of those things that one really shouldn't put all that much reliability in. Now if the manufacturers really wanted it to mean something then they'd either release the actual method or all adopt a "standard" (how about DOP's ) Even the manufacturers have/had issues with (system) accuracy statements, statistics (important word that, statistics) and to make it all sound better they invented the CEP spec. CEP, RMS 95% etc, why not simply accept the same accuracy spec from the same satellites that use the same principles. When one compares the old accuracy spec to the new, one of the main variables that is missing is the "user factor". Even if a unit was reasonbable (and they basically are BUT within reason) the user is a very uncontrollable factor . Many of the issues with estimated accuracy were highlighted when SA was set to zero as it became very evident very quickly that the manufacturers were "cooking" the numbers. Frankly they simply didn't reflect the real world and many were caught out. These days there's really not a lot of room to move and if one analizes EPE's against "actuals" one will generally find that the lows and the highs basically never show on the display. Again one could think the manufacturers are "fiddling" the numbers. Cheers, Kerry. I never get lost everybody keeps telling me where to go

But what really will say garmin accuracy mean to someone with another unit as any of this estimated accuracy/error stuff is simply that, estimated and relative to the method a particular manufacturer implements their own "accuracy estimation", and all manufacturers do that differently and unless all the different manufacturers are going to release "their" method then it basically means absolutely ziltch. Cheers, Kerry. I never get lost everybody keeps telling me where to go

"A very good GPS" is rather a broad comment but the model you refer does just the same job as any of the other makes/models used/mentioned here. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Many of the car navigation systems use miniture inertial system, which help with the issue of urban canyons. These little inertial micro's have extreme relative accuracy capability and are specifically used to counter this type of obstruction issue in cities. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Within reason all units won't be exactly the same but all will generally be within the accuracy spec. With the dynamics of the system and the user it really wouldn't matter if the type of GPS was known or not. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Johnnyvegas:ANd so we hear from Kerry, He has never found a cache, though he has been signed up for quite some time. Profile for Kerry (Kerry.) Member since March, 2002 Email this user Last visit: 5/19/2003 Caches Found/Hidden: 0/0 Travel Bugs Owned/Found: 0/0 Benchmarks Found: 0 Member since March, 2002 <----Hmmmmmmm. Trying this stunt again are we, AGAIN, short memory haven't you Johnny . Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by claypigeon58:Ever heard of Lowrance? Obviously some haven't but then some haven't heard about a lot of things. Cheers, Kerry. I never get lost everybody keeps telling me where to go

The extra precision being seen in the output is a function of the NNEA output. The NMEA spec allows for any number of decimal minutes and many units these days are fixing to 4 in the NMEA output as opposed to the normal 3 that one sees on the display (most displays are short on for extra display space anyway). On these types of units anything more than 4 is a bit of a con. Magellan's autoaveraging I don't beleive can be turned off. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Professional type of GPS totally different ballgame and dependent on how it's being used and in what type of mode. All have limitations and in reality a $30,000 GPS used in the same mode as a simple handheld really doesn't differ all that much. Side by side in SPS mode even what "could be" the most accurate GPS receiever won't differ from a consumer GPS. But 2 (or more) professional "style" receivers in static mode then this type of mode can be extremely accurate but can be time dependent (sometimes days) and must be post processed. The same 2 receivers in real-time can be very accurate as well but the range is limited by the radio system and distances that ambiguities can be resolved over. Then there's WADGPS (similar to WAAS) but world wide systems, which are subsrciption services, require decoders and the systems vary in order of accuracy the more accuracy the more one pays. Then there's a whole range of in between GIS, differential and other systems but relly one won't get any real accuracy from one receiver (without some help). That one receiever without any of the other bits could top the $20,000. Even the cost of some of the antenna's (alone) would shock the socks off ya. Cheers, Kerry. I never get lost everybody keeps telling me where to go

LDR, AOR-E isn't a WAAS satellite but EGNOS, which will be correction data for Europe, whenever the system is complete. Your receiver shouldn't want anything to do with that one. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Dave54:.... the more accurate the internal clock the more accurate the unit. What? the internal clock in the GPS receiver (I assume that's what you mean). Apart from basically telling the time it doesn't do anything for accuracy. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Lee David Rimar:Like real estate and geocaching, WAAS reception has a lot to do with location. At least from what I read ... I understand why WAAS wouldn't work in Australia, still not sure if it's a worhtwhile proposition in southeastern Michigan, USA. For sure location is everything but don't worry the "pin point accuracy" (in other words WAAS) has already been used as a selling point in Oz. One thing that was never really mentioned in all the blurb was, it doesn't work here. I know just a little minor oversight but some sales people will try anything. When that test was done some advertisements made all sorts of claims. I suppose the biggest sticking point with those that have to make it work (and fund it) is so far it has cost well over half (and not yet complete) the total cost of GPS, which is a global utility and yet the improvement in accuarcy and the area it covers simply doesn't relate back in $$ terms. From Lake Michigan (if that's anywhere near you?) AOR-W is around 28 odd degrees above the horizon and dropping as one moves west. Worthwhile ? something to actually try on the ground, so many variables. Cheers, Kerry. I never get lost everybody keeps telling me where to go [This message was edited by Kerry on May 14, 2003 at 05:41 AM.]

Only 2 satellites trasmit WAAS corrections and in part this is currently one of the weak links in the whole system. One is over the Pacific (178 deg east, you won't see this one) and the other over Brazil (54 deg west) and being Geo-stationary both are roughly over the equator. The one you will see will be about 35 degrees above the horizon so the signal shouldn't be all that bad providing your not behind any obstructions. If there's an obstruction then the only thing to do is for you to move as the satellite certainly won't. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Team Shabby, for sure if you have good reception, clear reception at a reasonable elevation then that's fine. When you say you "almost always" is that a function of location (wood, forest, city etc) or some other issue. I think with manufacturers if one does it (and in this case the primary contractor for WAAS has a little self interest in the system anyway) then business being business the others will follow as it is an open system. Where will WAAS be in few years time when civil dual frequency will have an accuracy around 1.5m globally without some of the restrictions that WAAS presents with. All this increased accuracy stuff is becoming a little blinding for some people, they want it but sometimes don't realize the whole situation. Take some of the boaties, have to have WAAS accuracy, need that "pin point" accuracy but in effect the distance between their sounder transducer and their GPS is greater than the accuracy of the system so it can be all rather a little meaningless, that's not useless just meaningless. Accuracy can mean different things to different people even to the point that until all receivers start displaying more than 3 decimal minutes in the output then again it can be a bit meaningless. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Certainly wouldn't rely on hit and miss signals in buildings. Would be rather simple for 911 purposes on mobiles but unfortuneately there's a sticking point, buildings/obstructions really don't give much reliability to GPS. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Real-world the affect of the WAAS signal/Non WAAS (SPS) outside the correction grid. Accuracy , it's not nice of one can't turn the thing off. everybody keeps telling me where to go

quote:Originally posted by 3fros:Huh? The satellites aren't all around the equator. From http://www.garmin.com/aboutGPS/ http://www.garmin.com/graphics/24satellite.jpg No, there not all around the equator but then there's NONE over the poles either, some call this the "scull cap" effect. So if there's none over the poles (north or south) then facing the equator puts that void area (extent depends a little on ones Lat) basically behind you. Garmin is a bit generic in their depiction, might look nice but From Me, the actual satellite tracks over the pole. What one would see if standing at 90 deg N, basically no sats above 45 degrees for the full 360 degree horizon. everybody keeps telling me where to go [This message was edited by Kerry on May 13, 2003 at 07:17 PM.]

quote:Originally posted by leatherman:Even that know it all kerry says WAAS is worth while. Did I say that maybe there's things missing but for the record I'll might clarify what I think . WAAS has it's place but it's certainly not the be all and end all of necessity. It's hellingish expensive for what improved accuracy it provides considering the area it services and some of the issues that still exist. WAAS appears to be currently caught up in a time warp, designed for/in the past but trying to survive in the present/future. Compared to WAAS other countries have developed (are developing) systems that fit the same application at a fraction of the cost compared to WAAS. As for being able to turn it off, maybe some are missing something here but GPS is a global utility, WAAS isn't and if one doesn't have the capability to turn the dam thing off then accuracy simply goes through the roof in by far the largest part of the world where WAAS doesn't exist. Why some actually want to leave it on come hell or high water I really don't know as it simply isn't practical for all users all of the time. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by 3fros: quote:Originally posted by smithdw:...and even in the way you hold it (your body may be blocking reception from another satellite). .... and pick up that satellite behind you. That why with a handheld if one tries to face the equator when possible this reduces that possibility, with any antenna. Cheers, Kerry. I never get lost everybody keeps telling me where to go

10 feet now that's a bit of a worry should have been more like 20 or 30 or 40 feet Cheers, Kerry. I never get lost everybody keeps telling me where to go