Talk:Global Positioning System/Archive 8: Difference between revisions

Revision as of 06:35, 19 June 2015

Revision as of 08:17, 26 June 2015

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*Both the equattion four four satellites or the least squares equations dfor more than four, are non-linear and need special solution methods. A common approach is by iteration on a linearized form of the euations, (e.g., [[Gauss–Newton algorithm]]).

**Ranging involves the receiver coordinates in a non-linear expression: R = sqrt(DX^2+DY^2+DZ^2), where DX = X_rec - X_sat. To invert four of more measurements for the unknown coordinates, we solve instead a simplified linear approximation, given by the partial derivatives: dR/dX_rec = DX/R, etc. [[User:Fgnievinski|Fgnievinski]] ([[User talk:Fgnievinski|talk]]) 20:24, 27 April 2015 (UTC)

== Proper name of the program ==

Around reference 20, we allege that the program's formal proper name has been shortened from "NAVSTAR GPS" to simply "GPS".

That reference, and other sources including the website of the NAVSTAR GPS Joint Program Office suggest that this is not true, and indeed, "GPS" is no longer sufficiently definitive, given the existance of the Russian Glonass and upcoming European Union Galileo systems. Unless someone can convince me that interpretation is incorrect, I propose to adjust that section, and move the page back to NAVSTAR, where it belongs.<br>--[[User:Baylink|Baylink]] ([[User talk:Baylink|talk]]) 19:04, 25 March 2015 (UTC)

:GPS is the name of the system of navigation satellites operated by the United States. The general term for satellite systems of this type is GNSS, or ''G''lobal ''N''avigation ''S''atellite ''S''ystem. The shift from GPS to GNSS has been reflected in the changing names of publications (e.g. [http://www.insidegnss.com/ Inside GNSS ]) and conferences (like the [[Institute of Navigation]]'s [https://www.ion.org/gnss/ GNNS+ conference]). NAVSTAR is indeed no longer the name of the system, and has not been for decades; it is simply the Global Positioning System, as referred to by the [http://www.gps.gov/ US government] and the [http://www.schriever.af.mil/GPS/ US Air Force]. [[User:Siafu|siafu]] ([[User talk:Siafu|talk]]) 22:04, 25 March 2015 (UTC)

::GPS is probably more in line with [[WP:COMMONNAME]] as well. Agreed that Glonass and Galileo fall under the category of [[Satellite Navigation|GNSS]]- the term "GPS" is enough of a distinction for the US system. Cheers! [[User:Skyraider1|Skyraider1]] ([[User talk:Skyraider1|talk]]) 00:44, 26 March 2015 (UTC)

:::I have always been rather suprised by the identification of 'a' GPS (system) with 'the' American GPS (system). We should split this article accordingly. [[User:Woodstone|Woodstone]] ([[User talk:Woodstone|talk]]) 12:00, 27 March 2015 (UTC)

::::"GPS" really is the name of the American system, and nobody uses the term "a GPS" to refer to such a system in general; the term for that is GNSS. The other GNSS's, namely [[GLONASS]], [[Beidou]] (sometimes referred to by the translation of "Compass"), and [[Galileo (satellite navigation)|Galileo]]-- or even [[QZSS]]-- are never referred to as "GPS" except by analogy. I'm unclear of the intent of your comment, but if you believe there is some ambiguity here, I would challenge you to present some sources that show it. [[User:Siafu|siafu]] ([[User talk:Siafu|talk]]) 03:26, 30 March 2015 (UTC)

:::::I think that what is stated in the paragraph above is just government-speak. The general public uses GPS as a generic term, according to the words it abbreviates. In daily practice the word GNSS is hardly used. [[User:Woodstone|Woodstone]] ([[User talk:Woodstone|talk]]) 03:58, 30 March 2015 (UTC)

::::::It's not just government-speak, it happens to be the terminology in use in the GNSS community. I can easily provide dozens of sources to back that up (there are a few given above already). In daily practice, most people use the word "GPS" to refer to GPS-based guidance systems, like when the car rental agent asks if you would like "a GPS", meaning something like a [[TomTom]]. IMO, relatively few members of the public are aware that other GNSS's exist, so ''a fortiori'' they aren't using it to refer to GNSS's in general. I would once again challenge you to produce some sources to back up your claim that the term "GPS" is used to refer to Galileo, GLONASS, Beidou, etc. [[User:Siafu|siafu]] ([[User talk:Siafu|talk]]) 08:03, 2 April 2015 (UTC)

I agree on GPS vs. GNSS but I disagree on GPS vs. Navstar GPS: all the latest official documents retain "Navstar" somewhere, e.g.: the Interface Control Document (ICD) -- also known as Interface Specification (IS) and User Interface (UI) -- is still titled "Navstar GPS..." as of 2014 [http://www.gps.gov/technical/icwg/IS-GPS-200H.pdf]; the "Standard Positioning Service (SPS) Performance Standard" is even more explicit: "The Navstar Global Positioning System, hereafter referred to as GPS, is a space-based radionavigation system owned by the United States Government (USG) and operated by the United States Air Force (USAF)." (the current version is admittedly a bit dated -- 2008) [http://www.gps.gov/technical/ps/2008-SPS-performance-standard.pdf]; the "Wide Area Augmentation System (WAAS) Performance Standard", Section B.3, Abbreviations and Acronyms, states: "GPS: Global Positioning System (or Navstar Global Positioning System)" [http://www.gps.gov/technical/ps/2008-WAAS-performance-standard.pdf]; not to mention the [[Notices Advisory to Navstar Users]] (NANUs). [[User:Fgnievinski|Fgnievinski]] ([[User talk:Fgnievinski|talk]]) 19:28, 27 April 2015 (UTC)

:The claim that the name has been shortened is sourced to Rip, "The Precision Revolution." I don't have that book but a search of the book on Google turns up 95 instances of "Navstar GPS" including a chapter title. Searches for things like "rename" and "shorten" turn up nothing. The first time the term "GPS" is used in the book, on page 4, the full name is given as "Navstar Global Positioning System (GPS)." Finally, the citation is for page 65, and there is nothing on that page about the name being shortened. I submit that the claim is not supported by the source. [[User:Kendall-K1|Kendall-K1]] ([[User talk:Kendall-K1|talk]]) 20:04, 27 April 2015 (UTC)

::Thanks; I wonder if we should mention Navstar more prominently -- not necessarily much more frequently -- in this page, e.g., "The official complete name of the system is "Navstar Global Positioning System"? [[User:Fgnievinski|Fgnievinski]] ([[User talk:Fgnievinski|talk]]) 20:35, 27 April 2015 (UTC)

==Least squares problem==

The current section of "6.3.1 Least squares" should not reside in "6.3 Solution methods" but in "6.1 Problem description". And furthermore, the following minor modifications are required:

:: "Using more than four involves an over-determined system of equations with no unique solution; such a system can be '''redefined as''' (not '''solved by''') a [[least-squares]] or weighted least squares '''problem''' (not '''method'''):"

::<math>\left( \hat{x},\hat{y},\hat{z},\hat{b} \right) = \underset{\left( x,y,z,b \right)}{\arg \min} \sum_i \left( \sqrt{(x-x_i)^2 + (y-y_i)^2 + (z-z_i)^2}- bc - p_i \right)^2</math>

[[User:Kkddkkdd|Kkddkkdd]] ([[User talk:Kkddkkdd|talk]]) 12:56, 21 May 2015 (UTC)---