Talk:Global Positioning System/Archive 2

message: This article seems a good technical explanation. Wikipedia though is an encyclopedia for everyone and the article needs, in addition, a plain English overview explanation for intelligent and interested entry level newcomers. Unfortuanately I dont have the knowledge to write this. Lumos3 09:43, 25 September 2006 (UTC)
thread_title:  Plain English 

message: I was going to revert the 29 sats back to 24 as well until I checked the satellite almanac at USCG navcen. Health code 000 means the satellite is healthy and I count 29 satellites. Am I counting wrong or is there something that says 24 somewhere else? --Dual Freq 23:49, 26 April 2006 (UTC)
replies: text: Seems like the number should be the number of satellites, not the minimum that they want to keep active at one time. The article / paragraph is about the GPS, not a position system. Davandron | Talk 14:16, 1 November 2006 (UTC)
thread_title:  Number of Satellites 

message: There is a presentation from the Sept 2006 GPS meeting which discusses how new miniature atomics could improve GPS:
PPT of Presentation. Think it might be good to integrate into the article, especially in a future improvements section?Davandron | Talk 19:19, 13 November 2006 (UTC)
thread_title: Miniature Atomic Clocks

message: The WGS84 article claims that
"WGS 84 ... is currently the reference system being used by the Global Positioning System."
Perhaps this GPS article should mention WGS 84.
If the D.O.D. wanted to convert the entire GPS system to some reference system *other* than WGS84, would that require sending up a completely new constellation, or is it "merely" a matter of reprogramming the ground recievers?
--DavidCary 05:29, 21 October 2005 (UTC)
replies: text: To say it shortly: A coordinate is useless as long as you don't have a reference system. Maps have a reference system, too, the most common is WGS84. All GPS-coordinates are natively WGS84-coodinates. If you have another (like ED50), you cannot plot your coordinate directly in the map, but you have to calculate the ED50-coordinate (It will make a difference of a few meters, but in some areas it can become up to 200 meters). --Lowfly 09:08, 2 December 2006 (UTC)
thread_title:  What is the relationship between [[GPS]] and [[WGS84]]? 

message: The bicycle application section added by 222.2.104.196 appears to be original research and needs sources. Without additional info, I'm not sure how the bicycle application is any different than navigating in an automobile. Davandron | Talk 01:05, 1 December 2006 (UTC)
thread_title: Bicycle Application

message: I moved a lot of older discussion topics to /Archive 1 as suggested by WP:ARCHIVE  --Michaelfavor 16:30, 7 December 2006 (UTC)
replies: text: A small sidebar: I remain concerned about the archiving, which is only a "technical how to" in the guidelines, and make the simple proposal that all moves err on the side of caution; waiting until its definately too big and the things being moved are definately old. - Davandron | Talk 17:52, 13 December 2006 (UTC)
replies: text: Michaelfavor, please do not edit my comments, even if you feel it would make more sense. The talk page guidelines (which you recently linked) discourages editing of anyone's comments, including your own, and marks it as unacceptable behavior. - Davandron | Talk 18:56, 14 December 2006 (UTC)
replies: text: I appologize if this upset you, that was not my intention.  I did not remove any of your words, or mis-represent your meaning, only refactored your comment slightly.  Since this seems somewhat off-topic for this page, I have posted a full reply at User_talk:Michaelfavor#Editing of comments.  --Michaelfavor 20:43, 15 December 2006 (UTC)
thread_title:  Older discussion topics moved to Archive 1 

message: I've re-written the section labeled "Techniques to improve accuracy" in order to improve that section and the whole article. A major goal was to convert the list to prose (per guidelines), and I ended up also migrating specific examples which had their own article into a link-through approach. 
The sections on Precise Monitoring are specific to GPS so they were left mostly intact. I didn't re-write the RPK section since I wasn't familiar enough with it. Can someone help there.
My edits left two things on the cutting floor, which need to find a home in the wikipedia:
#Wide Area GPS Enhancement (WAGE) is an attempt to improve GPS accuracy by providing more accurate satellite clock and ephemeris (orbital) data to specially-equipped receivers.
#Exploitation of DGPS for Guidance Enhancement (EDGE) is an effort to integrate DGPS into precision guided munitions such as the Joint Direct Attack Munition (JDAM).
Please help these orphan snippets by either linking them into the GNSS Augmentation article. - Davandron | Talk 23:33, 14 December 2006 (UTC)
thread_title:  Rewrite of Techniques to improve accuracy 

message: I'd like to add a modernization section which explains the new signals being added to GPS over the next few years. I'm going to develop the work in a personal sandbox and present it for integration in the future. If you would like to collaborate prior to integration, just use my talk page to leave me a note (i'm completely open to collaborating).
I'll be making the new section in a sandbox in part because I feel I should take a break from editing GPS to allow the community some time to review my recent copy-edits and generate feedback (if its needed). Thanks everyone - Davandron | Talk 05:42, 16 December 2006 (UTC)
thread_title:  Modernization Section to be added 

message: Hello,
I would like to propose that the page named GPS, which is currently a redirect to Global Positioning System, become the disambiguation page.  The main reason I suggest is that a GPS receiver is frequently referred to as "a GPS", and the person looking up GPS is highly likely to want to learn about a GPS receiver rather than the actual satellite system that runs it.  I believe that as many or more people looking up "GPS" want to know what "a GPS" (receiver) is as would ever be interested in C/A codes and ionospheric effects.
Such a page would start out saying something like "GPS stands for Global Positioning System."
* Global Positioning System, a system of navigation satellites
* GPS receiver, a handheld or vehicle-mounted navigation system
Then it would go on to list all of the non-navigation related things GPS can stand for.
Reswobslc 02:19, 13 October 2006 (UTC)
replies: text: IMHO, if one turns to an encyclopedia, they should expect a discussion of the proper noun first, with an "also see, ..." at the top for related but slightly dissimilar topics. I understand where you are coming from, and if GPS Receiver can stand on its own as a page then there should be a "also see" at the top, but Global Position System is GPS, where as GPS Receiver is not the same as "a gps." Its not a matter of disambiguation. Davandron | Talk 20:54, 7 December 2006 (UTC)
replies: text: In colloquial language, "a GPS" is a GPS receiver.  That's just how it is, as in "Honey, can you bring me my GPS?", or my car has GPS.  The job of a disambiguation or redirect page is to help people find what they're most likely looking for, and not to pester people with technicalities.  While Wikipedia's audience includes both lay people and engineers, there are a whole lot more lay people out there that think of GPS in terms of what's in their car or boat, and not what's in the sky, and that's why GPS needs to be a disambiguation page that includes GPS receiver.  See the comment above, under the heading Plain English, for a prime example of what I mean.Reswobslc 21:36, 16 December 2006 (UTC)
thread_title: The GPS redirect page

message: With this edit on 23:08, 19 December 2006, anonymous user 216.93.53.114 added a link near the top of the external links list to the website "gpshacks".  The site has minimal GPS content, most of it appearing within the last three months. The site is free but contains numerous Google-ads. Further, the user has a history of link-spamming.
I have removed the link, believing it to be link spam, please discuss if you feel it should be restored. - Davandron | Talk 23:28, 19 December 2006 (UTC)
replies: text: It looks a lot like linkspam.  That IP address has inserted material into the External links section of a good number of pages and has been warned repeatedly because of it.  The page itself looks like a blog with a lot of Google Adsense.  I'm comfortable with removing it. - Justin (Authalic) 00:32, 20 December 2006 (UTC)
thread_title:  Is GPShacks linkspam? 

message: I have added the following hidden notice, just below the External Links header. Since its encased in comment tags, it will only be visible when a person is editing near that section. The notice reads as,
  
  
  
  
  
  
  
  
Hopefully, this will help mitigate misunderstandings regarding external links. - Davandron | Talk 19:44, 20 December 2006 (UTC)
thread_title:  Hidden notice in article concerning links 

message: 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  tag with the  tag? - Davandron | Talk 16:08, 13 December 2006 (UTC)
replies: text: 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)
replies: text: 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)
replies: text: 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)
thread_title:  Featured Article? 

message: 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)
thread_title:  Reorg 

message: 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)
thread_title:  Daily Update links 

message: As I was organizing the links, I removed the following:
* University of New Brunswick, In Simple Terms, How Does GPS Work?
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)
thread_title:  Removed link 

message: 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
#If satellites are only synchronized to 1uS isn't that 300m error?
#Need to mention using a 4th satellite to correct crystal oscillator drift
#P(Y) Encryption's purpose
:I'll take a crack at them.
# 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.
# This is actually mentioned in the simple introduction. Perhaps it should be explained in more detail elsewhere in the article.
# 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)
thread_title: Control segment and Calculating positions

message: 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)
thread_title:  Additional Archives 

message: 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)
replies: text: 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)
thread_title:  Corrected DOD restriction information 

message: Removed this addition by 68.147.203.19
 * 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)
thread_title:  Potential Linkspam 

message: 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)
replies: text: 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)
thread_title:  Removed "gps to add 16-bit year" claim 

message: 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)
thread_title:  Industry Links