Kerry.

At the start of the Gulf war there were only 16 GPS sats in orbit and even in the Gulf they only provided 19-20 hours of 2D coverage (basically only 3 Sats in view) and 15 hours of 3D coverage. The GPS satellite launched on the day of the Iraqi invasion was activated in a record (then) 22 days. Following satellite launches were placed in orbits to maximize coverage in the middle east. One certainly wouldn't want to be relying on 18 sats to give a min of 4 sats world wide all the time as that's probably a little optimistic. It's possible in theory but the system specs start to flounder at around the 22 mark. There's only 5 planes and 6 slots in each plane and since the Sats have to orbit and the geometry has to be maximum to be effective it is a jugling exercise that doesn't specifically favor one particular spot on the earth as was highlighted in the Gulf War. Cheers, Kerry. I never get lost everybody keeps telling me where to go

The system being dynamic the number of sats you see will be different and change through out the day and this will also be different between different locations. Over 24 hours the average number one sees is "generally" 8 to 9 but ranges from 4/5 up to 12 and in some locations at times there's more than 12 but 12 channel receivers will only ever see 12 of these. What a receiver can see as opposed to what's in view can also be dependent on the receiver configuration and settings. Cheers, Kerry. I never get lost everybody keeps telling me where to go

NO, they won't need to turn it (war or no war) on but then it's never been turned off (as such) just set to zero. Cheers, Kerry. I never get lost everybody keeps telling me where to go

I can't see us getting WADGPS any time soon and not even latter than latter even with any miserable left over coverage from MSAT. The Cost v benefit simply ain't viable. Dual freq now that's going to be useful and not cost a arm and a leg. In a few years time some might look back and ask "WAAS" what WAAS that Cheers, Kerry. I never get lost everybody keeps telling me where to go

It appear (I would assume) to be the format and the mis-use of a decimal point. IF 37.69.2963N was "assumed" to be 37.692963N AND be assumed to be decimal degrees then that's 37 41.578'N (in Deg Min.mmm) and similar with 97.34.6977W "assumed" to be 97.346977 degrees then that 97 20.819'W Inappropriate use of a Decimal point and total lack of clarification as far as degrees minutes or seconds go etc Cheers, Kerry. 97.34.6977 I never get lost everybody keeps telling me where to go

Without making assumptions one really wouldn't have a clue what the format "really" is. One might/could assume (and that's not real clever at times) that it is decimal degrees but after seeing the many different variations with written formats that really one is only guessing. There should be absolute NO reason to guess a position format, none what so ever. http://www.cqnet.com.au/~user/aitken/gps/format.htm Cheers, Kerry. I never get lost everybody keeps telling me where to go

Well EGNOS or the ESTB (EGNOS System Test Bed) at the moment is nothing more than a test signal and basically provided in a research and development type mode. There is absolutely no guarantee or warranty what so ever, so anybody using this "as is" test signal does so at their own risk. The "Do Not Use" code is probably the best code to be in at present to cover ESA and any possible claims by those testing/using the signal "at their own risk" Cheers, Kerry. I never get lost everybody keeps telling me where to go

Egnix, the IIR-M is a designation for some of the existing built/stored IIR's that they have found a technical solution in modifying to give dual freq capability much sooner than if we had waited for the IIF's, which are specifically designed for dual freq (L2 and L5). There's roughly 20 odd IIR's constructed and in storage. Not all of these will become IIR-M's as some will be launched with the balance (~12 -15 ??) will be converted to M's. The IIR-M's besides having the additional L2(civil) also have new L1/M & L2M (military) signals. The IIR-M's are not quite a IIF as the IIF's will have the L5(civil), which the IIR-M's don't. What it means the system will be capable of dual freq (civil) much sooner than was originally planned but still some years off until there's enough sats to make civil dual freq useable. The first of the IIR-M's are supposedly due for launch late 2003 and the IIF's, 2008 so civil L1/L2 capability would probably be useful about 5 years sooner than waiting solely for the IIF's. Most certainly will require new receivers (hardware/software) but everything is backward compatible. Cheers, Kerry. I never get lost everybody keeps telling me where to go

No, if some want to regard it as "spying" then that's their opinion but obviously some haven't bothered to look (or want ot look) into what these types of systems are really all about. All these tracking/dispatch type of systems do have some real purposes, actually many purposes and some are more critical then others but if some think they are simply for "spying" then it's time to move on. However expect to see more and more GPS based "solutions" to all sorts of things. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Wadcutter:Yup. I played with one on Monday that's accurate to within 2 cm. Price is about $10,000. 2cm accuracy does need a little clarification as that's not basically possible from one "single receiver" but more a "system" and depending on the "type" of operation. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Yes, but they are a little bit more sophiscated than what one pays a few hundred $$'s for. Cheers, Kerry. I never get lost everybody keeps telling me where to go

But they are Geo-centric (with or without the hyphen) and apart from the inclined orbits they also have a relatively constant change (precession) from day to day. In other words at the same time each day the same satellite won't be in the exact same spot. Oh, and "Triangulation" is also a misused term as in normal use it implies angles but GPS is "distance" based. Cheers, Kerry. I never get lost everybody keeps telling me where to go

3 metres but there can be different types of 3 metres. Like 3 metres RMS, 3 metres CEP, 3 metres average, 3 metres @ 95% etc etc. All are 3 metres but they are all "different". SPS (Standard Positioning Service) accuracy is a function of the system that all receivers rely on. Effectively now that Selective Availability is set to zero the accuracy difference between military and civil units isn't all that great. About the only main difference is the L2 capability which handles some of the atmospheric issues as corrections and not predictions. Timing capability is also a little better. The system accuracy spec is based on a 24 satellite constellation and basically guarantees 13m @95% world average. That is also Signal-In-Space (SIS) as one hasn't any control of the user's situation. Worst case scenario accuracy spec is 39m @95%. Cheers, Kerry. I never get lost everybody keeps telling me where to go

I'm not sure what some are trying to say here but 3D, 7 parameter transformation sets (and all sorts of other transformation data sets for that matter) are used in everyday use by a wide range of every day people. There's no magic it's just maths. Cheers, Kerry. I never get lost everybody keeps telling me where to go

Ok the base underlying coordinate system is ECEF XYZ (relative to a datum) and the rest are simply and purely mathematical conversions. ECEF commonly known as cartesian coordinates but without a datum any coordinates be they whatever are totally (and that is TOTALLY) useless. It really depends on what the purpose of the coordinates but certainly some are more "user" friendly, but again depnding on the purpose, and the user. Cheers, Kerry. I never get lost everybody keeps telling me where to go [This message was edited by Kerry on February 22, 2003 at 04:23 AM.]

Not long, off the top of my head about 2 minutes max. Can depend a little on the receiver's software and logic but once it realizes it has lost lock then that's it. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by EraSeek:Yes, I must admit that I also wonder about some of this. AND Some info is conflicting. What I want to know is what occurs outside the coverage area when your unit is able to pick up a WAAS sat. Does it ignore the ionosphere data, not recieve it, use it anyway to some degree? What does it do outside the coverage area , terrorizes the hell out of the accuracy, big time. everybody keeps telling me where to go

Interference, can be that 5% unknown outside (>95%) the system specifications, there's no 100% guarantee with systems like this. Interference can be an issue as there's also currently issues with unlicenced use of Ultra WideBand (UWB) devices in conjunction with an FCC inquiry. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:"Navstar GPS is a satellite-based radio navigation system developed and operated by the US Department of Defense (DOD). GPS allows land, sea, and airborne users to immediately determine their three-dimensional position, speed and time, 24 hours a day, under all weather conditions, anywhere in the world. That about says it all but GPS is also used for weather forecasting, especially with regards water vapour. However one little cloud (even a huge cloud) isn't going to cause any problems that a recreational receiver will probably detect. If the weather became that extreme (and it has to be extremely extremely extreme) that signal was completely lost (have never heard this occuring) then the last thing one would be worried about would be GPS signal. Cheers, Kerry. I never get lost everybody keeps telling me where to go

As has been mentioned decimal degrees but as with all these types of published marks they generally should be used with caution. As someone mentioned, no mention of a datum, which fails the first co-ordinate rule, in that coordinates without a datum are suspect. Assuming the datum?, well one does that at ones own risk just depending on how critical it might be. Also it is sort of obvious what the format is (in this case) but what if say the Putin lat was 33.5815002 then what, more assumptions. Really I can't see the point why some go to all the trouble of publishing marks yet forget some of the more important issues, like a datum and making the position format "totally" unambiguous and yet go over the top with precision. Cheers, Kerry. I never get lost everybody keeps telling me where to go

PRN16 (GPS II-R8 / SVN56) was set usable as of Feb 18, at about 1600 UTC. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Dave54:.... or 1650763.73 wavelengths of the radiation in vacuum of the transition between 2p10 and 5d5 levels of the atom of Krypton 86. (Official definition in the Handbook of Physics). Dave, the Krypton 86 one was superceded (replaced) in 1983 by the light in a vaccum one. You'd think they'd make up their mind wouldn't ya Cheers, Kerry. I never get lost everybody keeps telling me where to go

A grid shift could be thought of as a less precise (simple) method of moving the grid lines (real world position) relative to the datum being used. Basically by changing datum's the grid lines move (shift), which are representative/related to the positions of fixed features as features on the ground don't move with a datum change. The relationship between datum's can be quite complex and for precise applications transformations or distortion models are used, where as for some applications/purposes grid shifts are adequate depending on the area of concern. For a single (reasonable scale) map the range might/could/can be negligible but for a whole country then the range difference is probably of some concern for critcial use. Cheers, Kerry. I never get lost everybody keeps telling me where to go

quote:Originally posted by Dave54:I hope we are not going to get into a quibble over the fifth decimal place of meter, a distance smaller than a period at the end of a sentence in the geocache logbook. You may have overlooked the ellipsis (...) at the end of the number, indicating it went on. Yes, worrying about that level of precision is counterproductive ..... No, only start quibbling when it becomes critical and that's a little more then the fifth decimal place (on most days) But if surveyors thought relative (in accuracy terms) as some do with the actual v perceived accuracy of recreational receivers then we'd really have to split hairs. Ah, don't worry it wasn't a serious comment, I know where your coming from. BUT how about we scrap those flintstone feet and just stick with metres , that's easy 1 metre = 1 metre (or the distance travelled by light in a vaccum in 1/299792458 of a second ) Cheers, Kerry. I never get lost everybody keeps telling me where to go

Poindexter, " anyway that's 3.28084'" was in reply to this "One UTM is one meter (3.2808... feet)" but I might see how you interpreted things as referring to 0.0001' However since you've raised the "length" of 0.0001' (latitude) now would 7.2912 inches be ellipsoid or plane distance and also sounds like around the 45 lat deg mark. At the equator 0.0001' lat is "only" round-about 7.2552 inches (on the ellipsoid). Cheers, Kerry. I never get lost everybody keeps telling me where to go