Kerry.

quote:Originally posted by Dave54:One UTM is one meter (3.2808... feet) State Plane coordinates are commonly in feet. No matter which system you use the smallest unit is well under the level of accuracy of your device so you end up with the old precision versus accuracy problem. And that's the whole point as it really doesn't matter as whatever system is way way less than the "actual" accuracy the system provides. Some of the units can now spit out 0.0001' but it really doesn't mean much unless put in context. anyway that's 3.28084' Cheers, Kerry. I never get lost everybody keeps telling me where to go

The "package" (as in software) will generally work as most GPSr's output NMEA but the software will be running on a PC/Laptop, with the GPS sending the Nav information via a serial data cable. As for getting those 3rd party type maps INTO a GPS then that's not in the manufactures list of things which they will allow. Cheers, Kerry. I never get lost everybody keeps telling me where to go

I suppose it depends on what type of accuracy those units are capable of and really it's the integrity of the position that is the key not necessarily the actual accuracy. There's nothing to assume they are "cm" accuarcy units anyway but more likely straight GIS type units, even thou they could have that (cm) option (IF installed as an option and GIVEN time). CM type accuracy with these types of single freq L1/CA units is possible IF the option is installed and with a minimum of 45 minutes observations and then only with post processing. They are best of classed as "sub-metre" units but can "post process" down to 10cm (given time) but when back pack mouted as they are then it's obvious that post processing is not what's being done but straight out GIS type surveys so accuracy is limited. In that regard it's the integrity in conjunction with the accuracy that one pays the money for but still only a real time position based on WADGPS (WAAS & others) augmentation type systems. Cheers, Kerry. I never get lost everybody keeps telling me where to go [This message was edited by Kerry on February 12, 2003 at 02:41 AM.]

Speed is horizontal based on XY and also includes doppler principles. In normal vehicle/walking type use it has to be very steep to have a noticeable impact on the difference. A skydiver, straight down, zero. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Probably future GPSr's will have more channels BUT this has to be put in prospective with regards many other variables. Almost regardless of ones location the biggest % of satellite availability will be in the 8 to 9/10 type range and any reciever which wants to use everything right down to zero horizon is really pushing the 12 channel myth. As for WAAS, it does have a satellite mask so only transmits corrections for satellites above that mask angle. Regardless if other satellites are visible if there's no correction data then one can't make use of them. Now if these people had mentioned a GPS+Glonass capability then 18 channels (even more with time) could be usefull but they don't and for the price one wouldn't/shouldn't really be expecting a dual system capability anyway. Faster acquisition solely due to having 18 channels, I would question that one but there's really not enough information (apart from what appears purely sales talk) to get a real impression. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Anders:.... Kerry, the satellite prediction software wants you to tell it which altitude you are on. Although I can understand that that makes a difference regarding how many satellites you can see from the earth, I'm not sure about what to set it to right now. My current elevation is about 140 meters above MSL. Does the GPS (in this case a typical consumer thing, the eTrex Vista) use it's altitude in the calculation of which satellites to see? Or does it apply some assumption, like sea level? Does it really matter that much, being in a farily flat part of the world, without any bigger hills around? I'm just trying to figure out if the altitude I set in the satellite software makes any real difference to the views I see on the screen, compared to the satellite view the Vista computes on its own. Anders Theoretically it probably does but practically one would probably not see any real difference considering that most planning software has max limitations in input and that input is fractional when compared to the earth radius and satellite orbits. Since this type of software isn't really required to be "precise", (in that say computed outputs are in whole integer degrees) the output is appropraite for the planning purpose. If you experiment with different heights (like 0 and 10,000m) and study the Azimuth and Elevation table (closely) one might see some "minor" variations, where an elevation is different (rounded) by a single degree (here and there). Have no idea how the Etrex thinks about things but it probably doesn't matter all that much. Cheers, Kerry. I never get lost everybody keeps telling me where to go

EPE (Estimated Position Error) with the emphasis on "estimated" as that's about exactly what it is, estimated, and next week with the next software revision it might be "estimated" a little different to what it was last week. Just because it might say 20' really doesn't mean your in fact 20' from where ever as it's really ONLY an estimate and nothing factual in an absolute sense. EPE is probably better treated as a relative measure in that 20' means the accuracy "might" be beeter than if it was displaying 30', basically 20' is a little better than 30' but not necessarily "really" 20' or 30 feet in the real world. Cheers, Kerry. Cheers, Kerry. I never get lost everybody keeps telling me where to go

It's an interesting question why WAAS has wallowed and really gone no where these past few years especially since SA was set to zero . WAAS badly needs that additional satellite as the present 2 give the system no redunancy what so ever. It will also be interesting how WAAS performance is (compared to), with the addition of L5. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by CreagerStone Family:What's the most important/relevant chart in the Leica program: the VISibility or the SUMmary? To me initially it's the DOP (PDOP/GDOP overlayed over the number of Sats) but depending on the requirements/situation some of the other charts can also be useful. By studing the DOP chart one might notice that there's no "absolute" correlation between the number of Sats and the PDOP/GHDOP. "Generally" the more Sats the lower the PDOP/GDOP but have a close look as the best times are basically when the PDOP/GDOP is the lowest, not necessarily when there's the most Sats. System accuracy specifications are based on a PDOP of 6 or less so above 6 (generally rare these days) one should be a little vary but to me the GDOP is more relevent. The SKY plot can be useful with respect obstructions especially when windowed. By graphically adding the obstructions then that generally has a tendency to change the overall plan (depending) and all the other plots. Really there's a lot of flexibility in most mission planning software but just make sure the Almanac is updated regularily. Also another interesting thing is to selectively toggle off (1 or several at a time) the Sats (vertical bar down the right hand side) and note the affect on the availability/plots. Cheers, Kerry. I never get lost everybody keeps telling me where to go

A bit of a killer at over 22mb for straight/simple mission planning software and does nothing more than all the rest. I'd be going with either leica's Satellite Availability http://www.leica-geosystems.com/gps/almanac/ or Ashtech's MP_win http://www.thales-geosolutions.com/skyfix/gpsinfo.html Cheers, Kerry. I never get lost everybody keeps telling me where to go

When on line GPS-IIR8 will show as PRN16 (SVN56). Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by El Oso:At the risk of digressing, my understanding was that consumer-grade GPSr's automatically used the four best signals. Is this not true? No, not neccesarily as there's a few other variables to consider. To the original question, with respect the accuracy, generally the more $$'s the more "accuracy" capable (with integrity) the "user system" (several user system options) might be. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Waterboss:Be sure your WAAS is enabled in your setup. Right now (and for some time in the future) anywhere outside the continential US WADGPS systems (such as WAAS) MUST be disabled otherwise accuracy will certainly be affected (for the worse). Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Poindexter:.... They do however make one false claim about USGS topographic maps and that is that they will always be in NAD27 datum. This is not the case as many newer ones are in NAD83. Mixed chart/map datum's will be a problem in many countries untill ALL are eventually converted along a common WGS84 theme. In the interim this issue is just another source for possible error as well as a issue for the map makers who have to extend the map sheets (in the interim) on the 2 sides where coverage falls short due to the different map datum's. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Average world wide Signal-In-Space system accuracy is 13m @ 95% (~42 feet) and worse case scenario 36 metres @ 95%. So your +/- 25 yards is basically in the realms of reality most of the time but half a mile does sound more like a user issue (not really an Etrex issue). Cheers, Kerry. I never get lost everybody keeps telling me where to go

Lat&Long / UTM or whatever can really be meaured in whatever one wants to measure things in, it really doesn't make that much difference. However just because it's UTM why does it have metre accuracy , bit of a myth that one. Accuracy is one thing and precision is totally another. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by elcamino:.... Some that have been launched in the past had technical difficulties and neve went healthy or died an early death. It's not really a problem (well it is sort of) but one of the biggest problems is many of the Sats have lived longer (way longer) than they were designed for, which sort of means we have to wait longer for the "better" replacements. What we need is more replacement "R-M's" then some IIF's Cheers, Kerry. I never get lost everybody keeps telling me where to go

They work (like everything else when they work) and had no real issues with Y2K but there was a software application that speeded up the re-acquisition depending on which software version was installed. 3.04 (or lower) required some user intervention with an auto locate reset sequence, which was simply holding PAGE + ON then leave stationary in an open area for about up to 20 minutes. The software application just helped the reset procedure but given time would basically fix itself following the reset. 3.05 and higher was ok. As a comparison on age version 2.03 was 1994. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Actually as of around 2.14pm EST, GPS II-R8 has separated from the Delta 2 rocket so if all things go to plan there should be an additional Sat up and running in a few weeks. That will bring the total Sats up to 27 (24+3) Cheers, Kerry. I never get lost everybody keeps telling me where to go

Currently there's 26. For quite some time up to a few months ago there was 28 but there's been 2 lost in recent times (21 & 22). There's slots for 32 all up but the system spec is designed around 24 operational with 3 spares but normally if not on maintainence then they have all been available. quote:the idle satellites are dedicated for use by Elvis Presley Actually the first satellite (SVN#1) was named Elvis and SVN#2 was Janis then the next got #3, #4 etc. The last GPS satellite launched was back in Jan 2001. GPS II-R8 is due for launch from Cape Canaveral Jan 29 sometime between 1806 & 1820 GMT. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Forester II:Kerry Most of my measurements are still in chains and tallys. Which consumer handhelds? I would like to check them out. Also what kind of accurracy? Yeah, still many old plans over this way in chains/links as well but I betcha you don't use a chain (as of the gunther variety) to measure those chains these days Many of the Garmin 12's, some of the Etrex's and some other garmin receivers can be made to externally record pseudo range (and limited carrier phase) in Rinex. Nottingham University http://www.nottingham.ac.uk/iessg/gringo/ produce a rinex logger called "Gringo" that has been tested with some of these receivers, and there's also a few "Async Logger" similar to http://mywebpages.comcast.net/dmilbert/softs/g12rin.htm Accuracy would probably best be classed as "metre" accuracy but that is of course dependent on baseline distance and reference station accuracy. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Feet and miles , does some still use them Forrester II, there's actually some consumer grade (handhelds) that can provide pseudorange and carrier phase for post processing. Not cm level accuracy but since only L1. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by GOT GPS?:.... Ive done Geocaches with both GPS units, and they amost go off in opposite directions, when within 100 feet of the cache. _3 experiments:_ 1) try the experiment with both GPS units within one foot of each other. 2)Put both GPS units several feet apart, and the antennas near each other. 3)Put both GPS units near each other, but the antennas several feet apart. Would item 2 be possible?? All 3 possible (including #2) plus a few other variations to the theme. However have never seen any indication (recorded or otherwise) that 2 antenna's, 2 GPSr's or any other combinations of makes/models of any affect on accuracy or operation. The main thing with running 2 antenna's (especially large aspect antenna) close together is any masking issues as that will show differences (artificial ones that really don't exist anyway). everybody keeps telling me where to go

quote:Originally posted by Cholo:When did time start? Time, which time (GPS time) precisely midnight on the 5/6 january 1980 and hasn't changed since quote: Where is W022.9823079 degrees x N5.1531416 degrees? What Datum and specific ITRF would you like that in Cheers, Kerry. I never get lost everybody keeps telling me where to go

10 degrees apart something needs to be clarified with that, 10 degrees what? certainly couldn't be 10 degrees in position , 10 degrees in bearing perhaps ??? Receivers running side by side won't have any affect on each other as far as signal reception etc is concerned. Different makes/models and same models will generally be different for many and varied reasons but the difference will still be within the spec. Cheers, Kerry. I never get lost everybody keeps telling me where to go