Sieghard,
As always, thanks for an excellent post with well-documented source material regarding GPS. Alan Lemly From: [email protected] <[email protected]> On Behalf Of Sieghard Weitzel Sent: Thursday, March 30, 2023 12:50 AM To: [email protected] Subject: About GPS systems and their accuracy For those who didn't read the thread about the "Differences in iPhone 14 models" here again what I posted regarding GPS accuracy. I wrote this in reply to a statement Kelly made about having heard that the iPhone 15 Pro may have 1 inch GPS accuracy. In particular he said "it may also have dual channel satellite navigation, giving location data as accurate as an inch compared to the 20 feet single channel offers" One inch accuracy is very difficult to achieve especially in cities between tall buildings and while a measurement over a long period of time may result in extremely high accuracy, most consumer devices cannot do this in most applications or without the euse of additional "augmentation systems <https://www.gps.gov/systems/augmentations/#:~:text=A%20GPS%20augmentation%20is%20any,the%20public%20and%20private%20sectors.> ", here the definition of what that is: A GPS augmentation is any system that aids GPS by providing accuracy, integrity, availability, or any other improvement to positioning, navigation, and timing that is not inherently part of GPS itself. Another article I read says this "Yes, there are GPS systems that can measure locations with accuracy up to 1 inch. These systems are known as Real-Time Kinematic (RTK) GPS systems. They use a fixed base station and a mobile receiver to calculate highly accurate positions." And here a page from the US government website about GPS accuracy <https://www.gps.gov/systems/gps/performance/accuracy/> , one highlight here is this: It will depend on the quality of your equipment, how many satellites are visible and processing in your equipment and the quality of the GPS signals (direct, reflection, interference). As measured by the Air Force that runs the GPS program, the error across the entire constellation of satellites was 2.1 feet, 95% of the time on 20 April 2021. Also, I hear sometimes people say the US government deliverately makes the GPS system less accurate; this is not true as of over 20 years ago, specifically in 2000 then President Bill Clinton put a stop to the so-called "selective availabbility" which was used throughout the 90's globally to make GPS signals for civilian use less accurate. On the GPS website it says " The United States has no intent to ever use Selective Availability again.". What Kelly referred to as "dual channel satellite navigation is technically called "dual frequency" or "multi band" and many of the newer Garmin GPS's including some of Garmin's watches already have this. Here an excerpt from an explanation from the Garmin website: What is Dual Frequency/Multi-Band GPS? Dual-frequency or "Multi-Band" systems use multiple frequency bands and allow for more consistent tracklogs and improved positioning when using the device in challenging environments. This means the receiver tracks more than one radio signal from each satellite on different frequencies, which can reduce errors caused by environmental interference. What Advantages Do Multi-Band Devices Have Over Other Models? • More consistent tracklogs and improved positioning when using the device in challenging environments (e.g. around tall buildings in urban canyons as well as tree cover) • Can achieve accuracy within about +/- 2 meters or 6 feet under ideal conditions versus the +/- 3 meters or 10 feet accuracy of other models • Detect (and reject) reflected satellite signals better than a single frequency receiver which improves accuracy • Better equipped to account for and correct errors that can be introduced by atmospheric effects (e.g. ionosphere errors) NOTE: Multi-GNSS satellite systems include GPS, GLONASS, Galileo, QZSS, BeiDou, and IRNSS (NavIC). Some satellite systems are not available in all areas of the globe. For more details, see https://www.gps.gov/systems/gnss/ I am sure the iPhone 15 Pro will undoubtedly be a fantastic device, but it seems Apple is differenciating the Pro models more and more from the regular models and then we have rumours of an iPhone 15 Ultra although I also read that this may possibly what Apple will call the iPhone 15 Pro Max and they will give it even more features or make it tougher than the regular iPhone 15 Pro. I guess we have to wait and see, but don't hold your breath that any iPhone in the near future will give you 1 inch GPS accuracy especially not in the places where most people live like cities with tall buildings and many sources of potential interference. For now the next big reveal will be iOS 17 on Monday, June 5 which Apple announced today is when WWDC will start. Then we'll wait another 3 or so months and probably on Tuesday, September 12 or so Apple wil lhave the fall hardware reveal although most rumours will have been confirmed at least a few weeks before then. -- The following information is important for all members of the V iPhone list. If you have any questions or concerns about the running of this list, or if you feel that a member's post is inappropriate, please contact the owners or moderators directly rather than posting on the list itself. Your V iPhone list moderator is Mark Taylor. Mark can be reached at: [email protected] <mailto:[email protected]> . Your list owner is Cara Quinn - you can reach Cara at [email protected] <mailto:[email protected]> The archives for this list can be searched at: http://www.mail-archive.com/[email protected]/ --- You received this message because you are subscribed to the Google Groups "VIPhone" group. 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