Talk:Differential GPS

WAAS not technically a DGPS

I removed / modified the following text from the article, but worry my edit is incomplete

The term can refer both to the generalized technique, as well as specific implementations using it. For instance, the FAA's WAAS system uses differential techniques to improve accuracy, broadcasting the corrections via L band satellite transmissions. Other examples of similar systems include the European Geostationary Navigation Overlay Service, Japan's Multi-Functional Satellite Augmentation System, Canada's CDGPS and the commercial VERIPOS, StarFire and OmniSTAR systems.

Technically, WAAS is not a Differential GPS system; it actually transmits updates regarding the GPS satellites themselves plus environmental delays, which is taken into account during the calculation process. This is different from DGPS which provides a "total error offset" or a "position error" which is simply added back into the local receiver's final calculated position. While the result (improved accuracy) is similar to DGPS, its a fundamental different process.

I am unsure about how the other systems operate, and so the reformatted text includes them, but this may need to be updated in the future. For instance, I believe the EGNOS is identical to WAAS, but am unsure how StarFire and OmniSTAR work. - Davandron | Talk 21:41, 14 December 2006 (UTC)

Australia's systems

what is going on for Australia 's systems? confusing. —Preceding unsigned comment added by 198.102.62.250 (talk) 18:13, 18 August 2008 (UTC)

Reference to "The" military is ambiguous

This probably refers to the US military, and implies that it is the only one in existence. Some people may find this point of view arrogant, ignorant, offensive, or all of the above. This should be corrected to refer to a specific country's mil.88.27.2|61.88.27.2]] (talk) 04:48, 2 September 2008 (UTC)

Or not. This article is about GPS, which is owned and operated by the US Government. It is preposterous to think someone would conclude that the Bosnian military or any other military would be dictating how to access the GPS system. Similarly, had the article been about GLONASS, and referenced the military, it would be equally preposterous to think that the US Military would be dictating usage of this, a Russian owned system. It isn't arrogant, offensive, or ignorant to assume the reader is able to make the connection between ownership of a system and control of that system. N0w8st8s (talk) 03:45, 18 May 2013 (UTC)n0w8st8s

Post-processing

As an example, it might be worth mentioning the UK Ordnance Survey's OS Net service, which offers free RINEX data from a network of over 100 reference stations across the UK.

The downside is that most consumer-level GPS systems (eg GPS-equipped Android tablets smartphones) don't expose the raw pseudorange and carrier-cycle data needed to create a corresponding Rinex file of their own to allow such post-processing. Jheald (talk) 07:58, 13 July 2012 (UTC)

re dubious

The following is labeled as dubious Through the early to mid 1980s, a number of agencies developed a solution to the SA "problem".[dubious – discuss] Since the SA signal was changed slowly, the effect of its offset on positioning was relatively fixed – that is, if the offset was "100 meters to the east", that offset would be true over a relatively wide area. This suggested that broadcasting this offset to local GPS receivers could eliminate the effects of SA, resulting in measurements closer to GPS's theoretical performance, around 15 meters. Additionally, another major source of errors in a GPS fix is due to transmission delays in the ionosphere, which could also be measured and corrected for in the broadcast. This offered an improvement to about 5 meters accuracy, more than enough for most civilian needs.[1]

Since the main GPS article says; After Korean Air Lines Flight 007, carrying 269 people, was shot down in 1983 after straying into the USSR's prohibited airspace,[13] in the vicinity of Sakhalin and Moneron Islands, President Ronald Reagan issued a directive making GPS freely available for civilian use, once it was sufficiently developed, as a common good.[14] The first satellite was launched in 1989, and the 24th satellite was launched in 1994. Roger L. Easton is widely credited as the primary inventor of GPS.

It is quite hard to imagine how a fix to GPS launched in 1989 through 1994 could have been fixed in the 1980s!

The reality is that the Canadian Military did not have access to the SA codes and quickly realized that differential GPS provided a solution. Buildings did not move. The officer in charge Halia (last name unknown), by 1996 had established base stations that reported their current location offset. (offset = How much the civilian GPS was lying/wrong regarding position) and the GPS devices were thus adjusted.

Knowing this solution would leak across the border, the USA acknowledged the civilian utility for accuracy would win, removed the SA limitation. — Preceding unsigned comment added by 198.103.184.76 (talk) 14:29, 16 January 2013 (UTC)

Corrections Needed

This article has much worthwhile information but contains erroneous and misleading statements as well. I am not qualified to correct it, but certainly somebody out there is. My concerns are similar to those that I described at under “Corrections Needed” at http://en.wikipedia.org/wiki/Talk:Real_Time_Kinematic#Corrections_Needed.

Firstly, Differential GPS does not require a network of base stations. There is no need for more than one base station to perform differential GPS. This fact is supported later in the article under the heading of “Post processing”. The statement might be true when addressing a specific system, typically consisting of such a network and a system for delivering correctors. The current content starts with out talking as though differential GPS were a specific system rather than a concept for improving accuracy of positions derived from GPS

Secondly, even if there is a network, it need not broadcast correctors. That would qualify it as an RTN as described in the linked “Talk”. Differential GPS does not require real-time correctors. The term applies to post-processed correction of a GPS derived position as well as RTK. — Preceding unsigned comment added by 167.131.0.194 (talk) 01:21, 19 January 2013 (UTC)

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Past tense in lede

The lede currently includes the text:

The USCG's DGPS was named NDGPS (Nationwide DGPS) and was jointly administered by the Coast Guard and the U.S. Department of Defense's Army Corps of Engineers (USACE). It consisted of broadcast sites located throughout the inland and coastal portions of the United States including Alaska, Hawaii and Puerto Rico.[2]

The use of the past tense here seems to be saying that NDGPS is no longer a going concern. If so, is it really worth mentioning in the lede? If it's still running, the text should be changed to the present tense ("The USCG's DGPS is called NDGPS (Nationwide DGPS) and is jointly administered ...") 80.3.250.140 (talk) 10:46, 5 October 2020 (UTC)

I agree, PLUS argue that the entire information about how this works in the US shouldn't be mentioned up there at all. It's enough to explain the situation in the US in the "Variations" section, like it is done for all other countries/regions of the world. -- Christallkeks (talk) 15:10, 27 March 2021 (UTC)