Talk:Global Positioning System

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[edit] Featured Article?

Theonlysilentbob tagged the article as a Featured Article Candidate (woohoo!) but, as Dhaluza commented, now probably isn't the best time for peer reviews (since there is on-going discussion for a significant edit). It's been pulled from the canidates page but do we also need to replace the {{fac}} tag with the {{facfailed}} tag? - Davandron | Talk 16:08, 13 December 2006 (UTC)

Well no one had an answer, and User:Raul654 just removed the tag, so I'm going to place the facfailed tag. Its worth noting that we might be ready for another FA nomination. - Davandron | Talk 20:10, 10 January 2007 (UTC)
I guess having the facfailed is more confusing than not having it, since the FA discussion article was deleted. Its easier to just resubmit than get a low-value discussion page restored. I'm going to take down the failed tag; do we feel the article is ready for a new nomination? - Davandron | Talk 21:34, 10 January 2007 (UTC)
I suggest a peer review prior to approaching FAC - a quick glance shows this article could benefit from peer review before approaching FAC. Also, please do not add the facfailed tag, as the article never went through FAC, and that will incorrectly categorize the article. facfailed categorizes articles in a way that we would expect to find a failed fac in the archives, and there was never a fac review. SandyGeorgia (Talk) 22:29, 10 January 2007 (UTC)

[edit] Kalman filter reference in GPS ground control

I have put back in the reference to the Kalman filter because, to be quite honest with you, the kalman filter is the heart and the soul and the life-blood of GPS. It is my ever consuming thought as we upgrade the GPS control system. Everything takes a back seat to the kalman filter in GPS control. You might as well not talk about GPS ground segment if you fail to mention it. You don't even need Kwaj, Cape, or any of the other monitor sites or ground antennas. GPS could fly just fine with other monitor sites and other Air Force antenna systems (it would be messy, but it would work). But without the kalman filter - there is no GPS. Its the black magic behind GPS that makes it go. It would be like talking about Hendrix and not talking about his guitar. the other steve jobs 1910, 22 December 2006 (MST)

My apologies for it getting dropped in the edit and thank you for resorting it. - Davandron | Talk 17:54, 23 December 2006 (UTC)
No problem. I am heartened by the professionalism and courtesy i've found here. As information is available and suitable, i'll bring it up here as is prudent. I will say that AEP is coming soon - that is not news - but trying to switch to it while keeping the constellation flying will make switching the engines on a C-130 at 20,000 feet seem easy. Fear not, there's a crack team working on it. the other steve jobs 1900, 28 December 2006 (MST)
I have re-edited the ground segment portion because it was reading very poorly with very long sentences. I also added some facts to be more accurate. 1. We also can fly the birds with AFSCN, not just GPS-owned GAs 2. We don't just rely on the GPS-owned monitor stations (we could actually be fine without them in a pinch) - we use many other monitor stations besides CAPE/KAWJ, etc. every day because kalman filters love data.
I also tried to make it smoother by putting the kalman filter reference (which was in the first sentence) over next to where we're talking about the inputs to it (which was in the last sentence) since that seemed to make more sense. I also referred to 2 SOPS as... well, 2 SOPS, because no one calls it day-to-day as the 2nd Space Operations Squadron, so i left the formal name in, and then started a new thought and called them 2 SOPS. I apologize to anyone who's worked on this - i'm not slinging mud and i appreciate all the hard work - but i read it, and by the 3rd time i read it as it was, it was still not making much sense to me. Hopefully, this change is okay. Yes... GPS ground segment is my life. It not only pays my bills, but its also very interesting to me.the other steve jobs 1400, 3 Jan 2007 (MST)
Its great to have a good resource such as yourself contributing. I may have undone your edit, but allow me to explain. In general throughout the article, acronyms are spelled out the first time they are used to aid in understanding what the mean. I think it should be the same for 2nd Space Operations Squadron and 2 SOPS as it is potential very confusing to a non-military individual. Once that first occurrence is spelled out, I think its perfectly acceptable to use 2SOPS throughout the article. - Davandron | Talk 18:33, 18 January 2007 (UTC)
Whoops! that was my intention, and obviously fat fingered it. Thanks for correcting it for me.! The other steve jobs 21:42, 22 January 2007 (UTC)

[edit] Satellite Launches/Decommisions appropriate for article?

What is everyone's feeling on the launch / decommission dates for the satellites being in the article? GPS meetings' presentations sometimes contain a stacked, horizontal bar chart (a form of timeline, i guess) showing the commission / decommission dates for each vehicle; providing a feel for how many active satellites there are and how old they are.

Perhaps a stand alone template or stub? - Davandron | Talk 17:44, 2 January 2007 (UTC)

Yes. I think its quite appropos. I mean, if we're talking about the USAF GPS system (which we are), this is the place you ought to be able to find all the data. If we don't put in a table, at least we should link to a page that has it. But its not like we're decomming birds every week - so i think its something this page should be able to keep up with. the other steve jobs 1400, 3 Jan 2007(MST)
I think this would need to be a stand-alone article. The GPS article is quite long already, and is still missing some important info and refs (I am working on researching and augmenting it). Properly done, the launch article should have lots of references, and this would also clutter up the main article.Dhaluza 00:16, 4 January 2007 (UTC)
Yeah it is a little too bit already... I think I'll author a main article titled something like "GPS Satellites" which could also explain the different blocks / versions then link it into the space segment. Thanks! - Davandron | Talk 03:00, 4 January 2007 (UTC)

[edit] Reorg

I wanted to add the GPS segmentation terminology, and had to do some work to organize the TOC hierarchy to fit it in. This lead to more changes to pull things together. I did it in steps to try to make it easy to follow, but the wiki change comparison does not work well with moves. Anyway, rest assured that I did not delete anything. I did add some intro text and formatting. Dhaluza 01:34, 3 January 2007 (UTC)

[edit] Daily Update links

UPDATE: I'm restoring the original link (keep both); apparently the problem was related to how I was connecting. From other connections I can see the files originally pointed to and they do contain a lot of information. Please disregard the original posting below - Davandron | Talk 03:20, 4 January 2007 (UTC)
I replaced

http://tycho.usno.navy.mil/gpscurr.html "Current GPS constellation, updated daily"

with this site

http://www.navcen.uscg.gov/gps/status_and_outage_info.htm

The original link seems to contain little information, and when I click the links I get authorization errors. The replacement is available everywhere and includes resources to understand what the status messages. - Davandron | Talk 15:29, 3 January 2007 (UTC)

[edit] Removed link

As I was organizing the links, I removed the following:

If you goto that page, it contains very little information, all of which appears in the main article and its sources already. However, we are all fallible, so please correct me if this is a valuable source. - Davandron | Talk 03:30, 4 January 2007 (UTC)

[edit] Navigation versus Aids to Navigation

I have loved using GPS for the past ten years, but as a former USAF Navigator, it's important for the reader's safety to prominently recognize that ANY electronic system is an aid to (something that eases or speeds determing your position) and not a substitute for navigation itself (accurately determining your position). Aids fail, batteries go dead, power supplies and wiring fail and the prudent voyager still needs to be able to safely get where they're going using manual means.

That's why both USAF and USCG call this and other system an electronic aid to navigation. Some recent deaths in the northwest may have been caused by overdependence on electronic navigation without manual back-up. So lets keep that critical word right in the beginning of the article, even though GPS is fairly reliable. The primary weak link in it is the user receiver's power source, and short of attaching AA cells to every fifth tree, that's not going to change. Thanks GCW50 17:10, 12 January 2007 (UTC)

GCW50, I completely agree with you that GPS can be an electronic aid to navigation, and we are in agreement with what actions are "best practices" in the world. However, this does not seem an appropriate warning or discussion for the lead-in of the article. And I do not agree with your usage of the world navigation.
I would link the discussion of navigation, but you have changed that article to re-enforce your changes here. So looking to the Merriam Webster dictionary, we find that navigation is associated not with a position-determination but with a course and distance, especially with regard to vessels. This seems at odds with your definition.
I'd ask for others to weigh in on this matter, to build a dialog of more than two individuals. - Davandron | Talk 03:06, 16 January 2007 (UTC)

Actually, the Meriam Webster dictionary says "the science of getting ships, aircraft, or spacecraft from place to place; especially : the method of determining position, course, and distance traveled" I don't see much difference with what I put in Navigation You always have to determine your postion first before you can lay a course to your destination. GCW50 14:42, 17 January 2007 (UTC)


[edit] Control segment and Calculating positions

On the Control segment text, we find that ...updates synchronize the atomic clocks on board the satellites to within one microsecond.... GPS uses time*speed-of-light as a distance measure, and 1e-6s*3e8m/s = 300 meters. So, this means that the satellites my GPS receiver is tracking may have a clock deviation between them of about 300 m! That's a bit different from the Satellite clock errors of +/-2 meters stated in Accuracy and Error Sources. +/-2 meters < 10nanoseconds. And this is a number that sounds better, otherwise why would we need atomic clocks... In fact, the error between satellite clocks is assumed to be very small, so that the basic equations used in the kalman filter (or least-squares algorithm) that yield the position solution, assume it to be included in a white noise component that represents all the unmodelled noise sources. This brings me to the second comment. The satellites use atomic clocks, but the GPS receiver uses a crystal oscilator. Good clock error models and some electronic advances make these clocks very good already, but just as the atomic clocks are constantly being corrected from the main control centre, so must the receiver clocks also be corrected. This is done at the receiver, by introducing a 4th unknown in the equations, the receiver clock bias (the other 3 are x,y,z or lat,lon,alt ...). The receiver-clock-bias*speed-of-light is a distance, an error which will be common to all satellite pseudorange measurements. That's why we need to see at least 4 satellites and not just 3. This is not mentioned there. My final comment goes for the paragraph Calculating a position with the P(Y) signal ...The encryption is essentially a safety mechanism... in Calculating positions. The pseudo-random sequences have a bit more magic about them than what is described here. They are periodic, therefore pseudo-random, but would they be infinite random sequences and the result of the correlation in time between any 2 different sequences would always yield zero. This is the fundamental aspect behind the fact that you can receive simultaneously on the same frequency, the signal from multiple satellites. Once a correlator choses a satellite ID, that pseudo-random sequence will correlate very well with itself and very poorly with all others. In fact, this way of transmitting digital information allows the signals to be reachable to the receiver when their power is already bellow the background noise level. In other words, the encryption is not just a safety mechanism to distinguish between real and whatever satellites. If you don't have the key, you cannot produce an identical P sequence, therefore you need certainly more than week computing power to manage to decode the information using some brute-force method... and then, they change the key and we go back to square 1. If the only reason preventing us from reading the P code would be the kind of things that happen on a war-like scenario, I think most of us living in peacefull places would have already found a way to read it anyway and cancel that ionospheric delay once and for all. At least, while there's peace there would be 30cm accuracy against 15m :). My personal comment on the way this particular paragraph is written is that it sounds way to much like "the war on terror", the "be affraid, be very affraid" kind of feeling that we Europeans feel to be so strong on the US. The RAIM will not help us! Oh my god!... —The preceding unsigned comment was added by 130.161.79.207 (talk • contribs) 20:27, 18 January 2007 (UTC)

WOW thats a lot... lets see if we can break it apart into what you are saying / talking about
  1. If satellites are only synchronized to 1uS isn't that 300m error?
  2. Need to mention using a 4th satellite to correct crystal oscillator drift
  3. P(Y) Encryption's purpose
I'll take a crack at them.
  1. There appears to be a misunderstanding between time transfer (the act of synchronizing the clocks) and the accuracy of the clock. While the atomic clock is repeatable to a very high standard, its synchronization to the reference station is only repeatable to 1uS. This does not impact the navigation component. It would matter if you were trying to synchronize your clock to the reference clock used by the gps control network.
  2. This is actually mentioned in the simple introduction. Perhaps it should be explained in more detail elsewhere in the article.
  3. You mentioned many things about the P(Y) encryption. Here is a short answer. Yes, the very long PRN increases correlation gain, however thats just the P-code. Relatively recently, they decided to encrypt the long P-code, and thats where the Y part comes from. Believe it or not it is primarily as an assurance / antispoofing. As I understand it, the encryption not to stop someone from post-processing the data and decrypting the code, its to stop someone from correctly encrypting a fake signal and introducing intentional error into those accessing the P(Y) channel. By the way, you'll be happy to know smart people have figured out how to use the L2 data stream to cancel out ionospheric delay. This is called codeless or semi-codeless multifrequency decoding and its used in the survey industry. Thats a peaceful industry that likes high-accuracy, but its not easy to do (and the smart people like getting paid to figure it out).
I think all the issues you raised are already covered in the article, and hopefully my explanations help. If people reading this feel that the article needs to be expanded, please feel free to discuss who we should do that. Enjoy. - Davandron | Talk 21:41, 18 January 2007 (UTC)

[edit] Additional Archives

This talk page is pretty active! It's hard to strike the size / discussion balance. I've moved the discussions which were last commented on in November 2006 into /Archive 2 and given it the title November 2006. There wasn't a lot, so I think when we're ready to move December 2006, we should move it into Archive 2 and change the link-text to read as such.

I would like to keep 2 months of discussion on this page, but that might be hard. How does the group feel about performing an archiving on Feb 1st of the discussions last commented on Dec 1 - Dec 15? Will those be old enough? - Davandron | Talk 22:17, 18 January 2007 (UTC)

[edit] Corrected DOD restriction information

Under the military section, it stated a general speed limitation of 515m/s and that no GPS receiver can operate above 18km. This restriction, which only applies to civilian recievers, is incorrectly stated. Both conditions must be present (18km+ and 515m/s+) in order for the GPS to cease providing information. I've used commercial GPS recievers in high altitude balloons on 2 occasions that exceeded 18km, but not 515 m/s without a problem. Achilles03 15:56, 19 January 2007 (UTC)

Thanks for clarifying that subject. I've edited your entry to removed a redundancy, and took the opportunity to improve the copy of the section as a whole. - Davandron | Talk 18:28, 19 January 2007 (UTC)

[edit] Potential Linkspam

Removed this addition by 68.147.203.19

* [http://www.gpspolice.net/videos.php GPS technology fights crime.] 
 CTV news broadcast (video) of how GPS technology helped RCMP break-up a crime ring.

This user previously added a similar link (Dec 28th) to a similar article. - Davandron | Talk 14:09, 22 January 2007 (UTC)

[edit] NGA Monitor stations

Sorry for the coyness of my addition of the text "and other sources" with reference to what feeds the Kalman filter with L-band data. This [1] makes it plain that its open source that we're using NGA data to feed the machine. In fact, its a huge help and will only get better in the future with more NGA sites coming online in the future, since we'll be able to "reverse locate" the birds - as in, you find your position by seeing 3 or more birds now, well, we'll be able to see their precise location by using 3 monitoring stations at any given time. The other steve jobs 21:39, 22 January 2007 (UTC)

Great find on the source! We actually had an edit conflict because the original link (to the email list) probably wasn't reliable enough for Wiki-standards. This new one is a lot better. If you know of some more data on the NGA's website or in some presentations made by your colleagues, that might help too.
BTW, I went ahead and reformatted your source/reference so that its a reference-noted format. Its a requirement for articles that want to get the WP:Featured Article status. - Davandron | Talk 21:54, 22 January 2007 (UTC)
NGA didn't change their name from NIMA to a 3 letter acronym that ends with "Angecy" because they want to tell the world about what they do. ;-) For the record, I will always tred on the side of too cautious because i have no desire to put the mission in jeopardy in any way - so please forgive me and feel free to remove any edits that don't meet Wiki standards, and i promise not to be offended. As for now, like the link states, they've got their monitor stations and they're feeding their data to us so as to make the NAV messages better. Honestly, they're a black box that has a spigot to us, and that's really all we need to know. The other steve jobs 20:09, 24 January 2007 (UTC)

[edit] Removed "gps to add 16-bit year" claim

I removed the following unsupported claim

A new field is being added to the GPS navigation message 
that specifies the calendar year number exactly, in a sixteen-bit field

after double checking both the current or purposed modernized specifications. There was no mentioned anywhere of this addition. If someone has a reliable source that this is being added, please feel free to restore the text. - Davandron | Talk 19:47, 23 January 2007 (UTC)

Not going to happen. In coversation with the person on planet earth that would have to know about it in order for it to even be an idea (they'd have to go to his group to discuss the operational feasibility), he didn't have any idea what i was talking about. --The other steve jobs 20:47, 24 January 2007 (UTC)

Small Update: In the process of researching for the L2C and L5, I did learn that these new signals will use a 13-bit GPS week number (instead of the 10-bit currently used), which means it will only return to zero every 157.5 years. So, instead of needing to know the current decade, you will only need to know the current century... provided, of course, that GPS L2C signal is still around in the year 2138! Perhaps this is the change the original claim was referring to. - Davandron | Talk 20:56, 30 January 2007 (UTC)

[edit] Accuracy and error sources

Since GPS signals propagate nearly at the speed of light, this represents an error of about 3 meters.

Why "nearly" the speed of light? Being EM radiation, wouldn't they propagate at the speed of light? --Marainman 20:27, 24 January 2007 (UTC)

Well, believe it or not the speed of propagation changes depending on the material that the radiation is passing through. In the case of our atmosphere, its pretty close to the speed of light in a vacuum but isn't exactly the same. Check out speed of light. - Davandron | Talk 23:37, 24 January 2007 (UTC)
OK, makes sense now. I wasn't thinking nearly "nearly" enough. I suppose when we're talking about comparing signal timings from only thousands of miles away, that little bit can make a big difference. --Marainman 17:03, 25 January 2007 (UTC)

"Position accuracy can be improved by using the higher-speed P(Y) signal." This isn't clear to me - higher-speed than what? AndrewWTaylor 13:02, 1 February 2007 (UTC)

Higher speed than the C/A code. The P(Y) code is ten times faster, so has 1/10th of the bit-position error factor. I'll see if I can improve that paragraph. - Davandron | Talk 15:59, 1 February 2007 (UTC)
thanks - I think it's a bit confusing because the sentence comes right after the bit about signals propagating at near light speed. AndrewWTaylor 21:59, 1 February 2007 (UTC)

[edit] Industry Links

Recently, anonymous user 81.255.195.105 added / proposed an Industry section of the external links, and added only the Magellan link. I removed this addition due to concerns about WP:EL, but it does raise the question; should we provide links to the manufacuters of GPS receivers? If so, which ones should be represented? - Davandron | Talk 17:39, 26 January 2007 (UTC)

  • Oppose (weakly): While I like the idea and thank the user for adding it, I think its very thin ice and probably inappropriate for wiki; its not the wiki's job to provide a directory of manufactures, and the article itself is not about manufactures. - Davandron | Talk 17:39, 26 January 2007 (UTC)
  • Oppose: Instead, how about one external link like this?: Pricegrabber.com GPS receivers —EncMstr 17:44, 26 January 2007 (UTC)
  • Oppose: I think it would be more interesting to talk about the _actual_ recievers - the families of commerical GPS receiver chips out there. Garmin, Megellan, etc.. they all use those receivers in their... receivers. The history of how GPS receivers have gone from backpack-sized to now the size of a rice grain is even more interesting to me - from 4 channel receivers to now standard 12 + WAAS, etc. Its an incredible history. But consumer GPS receivers are approaching commodity status, with the only real differentiation being who's got the better software, and even THAT is becoming commodity rapidly. The other steve jobs 17:42, 30 January 2007 (UTC)

[edit] Can anybody suggest how to control the fuel consumption on a car with GPS?

One of my cars has GPS on it. And I wonder how can I control or check out of fuel consumption with the program working with that GPS.

Thanks for further. Am - 124.120.77.228 09:25, 13 February 2007 (UTC)

Hello 124.120.77.228, the wikipedia is not intended to be a general forum, so questions and discussions only loosely associated with the article are discouraged. You might try asking your question in a gps forum, like GPS Passion's Forum. Good luck! - Davandron | Talk 13:56, 13 February 2007 (UTC)

[edit] Article structure

I think the 'Applications' section should be moved back to the top of the article. It was moved further down based on the idea the article should be arranged "What it is, How it works, When it came to be, How its used.", but I have been unable to find any reference for this structure. It seems to me that Inverted pyramid, Spiral approach, and items on the current duscussion page all tend to indicate this section should be moved back near the top of the article. --Michaelfavor 23:47, 16 February 2007 (UTC)

The "list of applications" seems less encyclopedic and more what wiki is not than the remainder of the article. I'm curious to understand why you would put this at the top? Can you cite any similar Featured Article that was formated this way; with an applications section first, then info on what it is or how it works? In a quick search I found none in that format, however both Radar and Compact Cassette use the current format. - Davandron | Talk 05:37, 17 February 2007 (UTC)

[edit] Missing 15m Relativistic correction?

I'm probbaly being dense here, but I've read Neil Ashby's piece and I can't find mention of the cited 15m claim. (He does talk about an 8m correction for orbital eccentricity on the top of page 8.) Can anyone point me at where he says there is a 15m correction? --Fuchsia Groan 14:28, 2 March 2007 (UTC)

I was unable to reconcile the 15m note with that article, so you're not alone. I'd guess that the 15m figure was original referenced by the IEEE presentation in the following sentence. That said, if the physics today article covered all the relativistic effects, then it should be able to yield the same result. So, we probably need to clean this up (either the article is wrong, or one of the sources is wrong). - Davandron | Talk 03:40, 3 March 2007 (UTC)
In my edits I went ahead and pulled it. If we find a way to usefully incorporate it, we can put it back in. The chunk in question was
The error introduced by relativistic effects can be as much as 15 meters. The GPS system also makes adjustments for the relativistic drift of the atomic clocks in the satellites. Parts of this correction are carried out in the satellites and parts in the receiver.<ref>Deines, "Uncompensated relativity effects for a ground-based GPSA receiver", Position Location and Navigation Symposium, 1992. Record. '500 Years After Columbus — Navigation Challenges of Tomorrow'. IEEE PLANS '92.</ref>
- Davandron | Talk 05:10, 3 March 2007 (UTC)
That's good work. It would still be nice to have a distance figure - it gives you a "feel" for the significance of Relativistic effects. (In a dense English housing estate, 15m would be the wrong street.) BTW this is the IEEE Paper cited above. (Although I'm not a subscriber.)
--Fuchsia Groan 10:40, 6 March 2007 (UTC)
Thanks for the kind words and good find on the paper.
After the rewrite, one of my concerns with a section discussing "errors due to relativistic effects" is that all of the currently listed effects are compensated for; they shouldn't show up as errror in a position fix. The other error sources are all present, though some are addressed with certain techniques; ie dual frequency, WAAS, etc. At the same time, I think its important to describe the relativistic impacts so that people know what they are and how they are compensated. Does that make sense? - Davandron | Talk 13:44, 6 March 2007 (UTC)
Yes, that makes sense - but there seems nowhere else to put it!
Anyway, Neil Ashby says that the corrections vary from manufacturer to manufactuer, with not everybody correcting for Sagnac, so it may be there are real relativistic errors in a position fix. And the corrections he outlines are only approximations, ignoring higher order terms, so there is a tiny residual relativistic error.
--Fuchsia Groan 19:04, 8 March 2007 (UTC)

[edit] Interesting RAND org article to maybe integrate

I just stumbled onto this article at the RAND organization and in a quick glance through it might have some good content to integrate. I'm a little busy at the moment, so if someone else can use this before I get to it then go for it. - Davandron | Talk 03:09, 6 March 2007 (UTC)


[edit] Question re GPS History

Greetings! It isn't clear to me from the article when exactly the restrictions were removed on civilian use of the GPS (so that everybody could receive the more accurate signals previously limited to the US military). Was this Clinton's 1996 change, or when exactly did this happen? It would be nice if someone would update the article to clarify this. Thanks! :-) —The preceding unsigned comment was added by 152.216.11.5 (talk • contribs) 15:27, 23 March 2007 (UTC)

I believe a civilian-usable signal was aways available; there were no restrictions on recieving it. I know that in 1983 Reagon said it would be made available to the public. What Clinton did was remove an intentional error source (called selective availability) which made the civilian signal significantly more incorrect than the military signal.
I'll see if I can make that a little more clear in the article. - Davandron | Talk 17:37, 23 March 2007 (UTC)

[edit] Wikiproject Aviation

I'm not overly familiar with the wikiproject program, but this article covers far more ground than the aviation group alone. Should every project be invited to tag the talk page and assess it to their criteria? Seems like we'd end up with a long list of tags, and conflicting quality ratings. The tag was applied as part of a mass tagging (almost looks like a script), not apparently by someone who felt it was appropriate for this specific article. I yanked the tag for the time being, and invite the organizers of the aviation group to discuss here how they would improve the article. - Davandron | Talk 13:51, 24 March 2007 (UTC)

I've re-added the {{WPAVIATION}} banner because it falls (at least in part) under that projects scope. If other projects feel the article falls under their scope as well they may add tags to. If it seems like there are too many tags then there is the {{WikiProjectBanners}} template to help combine them. This is all part of the Wikipedia Version 1.0 assessment drive. It may not cause an immediate improvement in this article, but will hopefully allow it to be seen by more than just those who are currently interested in editing it. - Trevor MacInnis (Contribs) 06:13, 25 March 2007 (UTC)
I respectfully disagree, but we'll see. If your team gets around to rating the article, within say a month, then the community will know you're serious and not just soaking up articles. In the mean time, Military technology and electronics seem very apt projects for this to be tagged with. - Davandron | Talk 16:32, 25 March 2007 (UTC)

[edit] Trilateration or Multilateration?

Does GPS use Trilateration or Multilateration? (aside: both of those wiki pages refer to GPS). AndrewRH 15:02, 30 March 2007 (UTC)

I think the multilateration is adding a condition to its definition that isn't universally agreed with; namely the absolute requirement of Trilateration. If thats the case, they are effectively the same thing, see Talk:Multilateration#Merge. - Davandron | Talk 19:51, 30 March 2007 (UTC)
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