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  1. #31
    iPhone as a wifi device
    MacInWin's Avatar
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    Not withstanding Sygic's over-the-top claim to be first, there are two types of GPS navigation systems out there. I used to write professional articles on GPS systems when they were first coming out, when the accuracy of GPS was permitted to be used by civilians by the DoD to a level where it was practicable to use as a navigation system for cars.

    If you want to know more about how it works, keep reading, otherwise you can stop now.

    The two types of GPS navigation systems are what I will call on-demand and on-device. The difference between the two are where the maps are stored and where the navigation is performed. On-demand systems are dynamic in that they store the maps at some location in the cloud, downloading what you need for the route you ask for when it is planned. The planning can be done either at the mothership (as in Waze) or on the device. So the on-demand approach requires connectivity to the mothership, either by cell or wifi. And what happens without the connection varies. Waze, for example, plans your route and downloads the maps you need for that route at the start, so that it can show the entire route for you. And as you navigate, it constantly updates for traffic, obstructions, police, etc, etc. If you lose connectivity, it will use the last calculated route for you but it will tell you it has lost that connectivity and it won't update the route for those outside factors. Nor will it recalculate if you leave the planned route, as all planning is done at the mothership. I have a route I use it for fairly frequently and there is a 20 minute stretch with no cell service, so Waze complains for that 20 minutes. Once back in coverage, sometimes it automatically connects, sometimes it seems to have given up and won't connect unless I stop it and restart it. I suspect Apple and Google maps work the same way.

    The on-device navigation systems are, as it sounds, on the device and can be used with zero external connectivity. Of course, if you want traffic, or dynamic routing around accidents, incidents, construction zones, etc., you will need some sort of connectivity. So when Sygic, for example, offers traffic updates, it is assuming you have that connectivity. No connectivity, no avoidance navigation.

    So which is better? Depends. On-demand requires connectivity for just about everything. Although the "local" map may be on your device because that was the last one you used, if you use On-demand and want to go someplace new, particularly if it's far away, those maps for that route will need to be downloaded for you. But the advantage is that you get the absolutely latest information, including traffic delays, in near real time. On-device has the advantage of working without any connectivity at all, but you have to dedicate storage for the maps you *might* use, even if you aren't using them very often. Right now, I have an on-device navigation system called CoPilot GPS with all the maps for North America (US, Mexico, Canada) and it takes 3.61GB of storage. I also have Waze and it is reporting 108 Mbytes, or about 3% of what CoPilot is using.

    As for accuracy, GPS for cars is accurate to about 5 meters (16.5 feet). That's good enough to use on the road as most of the system use a feature called "snap to road" that assumes you are ON the road, even if the most recent fix is not. Theoretically it is possible to have accuracy to within millimeters, if you want to step up in price to a dedicated GPS system. (Think Google Maps and Apple Maps cars driving around. I suspect they have a more accurate GPS to get the maps as accurate as they can.) (Geologists also track movements of the earth along earthquake faults using high-accuracy GPS receivers.) Cell tower triangulation can help get a bit more accuracy, which is why you see that nag notice if you turn off cellular and just use GPS. The improvement with cell triangulation is to about 5 feet, which is handy in cities where the bouncing signals from GPS can make it less accurate. I suspect 5G will enhance that triangulation, but I haven't seen any figures on it.

    GPS is degraded if the satellite "constellation" above you is out of optimum shape. When a satellite gets low in the sky the bending of the signal through the atmosphere can make a few nanoseconds worth of error. (A nanosecond of error is just under 1 foot, so a delay of 15 nanoseconds would give you an additional 15 feet of error, for a total of 30 feet of error.) Bounce is even worse as every foot of added distance for the signal in the bounce degrades your position by that same foot. That's why GPS wanders around in cities as the signals bounce all over the place. Recent launches of additional satellites has significantly reduced the "bad constellation" instances and the logic in the calculations says, basically, "5 of us agree we are HERE and you single satellite vote THERE. We will use HERE."

    Some systems will let you view the GPS data as it comes in. "Back in the day" you could actually see the constellation of satellites being used for the fix, so you could judge for yourself the accuracy. I haven't done that in years--no need for it with all the satellites that are currently up.

    If you want more boring tech details, PM me. No need to bore the rest of the visitors to the forum!

    EDIT: Added a bit of clarity on Waze navigation being done on the mothership.
    Jake

  2. #32
    iPhone as a wifi device
    pigoo3's Avatar
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    Quote Originally Posted by Lifeisabeach View Post
    Alright, so here is what I can confirm. I set up an old iPhone 5s to navigate to work using Apple Maps, then turned wi-fi and bluetooth off before plugging it into my Pioneer head unit. I have no SIM card in it so I was 100% off the grid. I only have a 10 minute drive to work, so Maps was able to preload my route and streets in the general area. As I was driving, the map display remained quite accurate with voice-over directions working until I strayed off route to get coffee. The roads for the area were still loaded and Maps continued to show my correct GPS location even off route. Once I was back on route, the directions resumed.

    So, given my limited trial, I think you can expect pretty good GPS accuracy with at least an iPhone 5s and newer even if you aren’t connected to a hotspot.
    Super awesome sir. Thanks for the real-life experiment & positive results.

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  3. #33
    iPhone as a wifi device

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    Quote Originally Posted by MacInWin View Post
    Not withstanding Sygic's over-the-top claim to be first, there are two types of GPS navigation systems out there. I used to write professional articles on GPS systems when they were first coming out, when the accuracy of GPS was permitted to be used by civilians by the DoD to a level where it was practicable to use as a navigation system for cars.

    If you want to know more about how it works, keep reading, otherwise you can stop now.

    The two types of GPS navigation systems are what I will call on-demand and on-device. The difference between the two are where the maps are stored and where the navigation is performed. On-demand systems are dynamic in that they store the maps at some location in the cloud, downloading what you need for the route you ask for when it is planned. The planning can be done either at the mothership (as in Waze) or on the device. So the on-demand approach requires connectivity to the mothership, either by cell or wifi. And what happens without the connection varies. Waze, for example, plans your route and downloads the maps you need for that route at the start, so that it can show the entire route for you. And as you navigate, it constantly updates for traffic, obstructions, police, etc, etc. If you lose connectivity, it will use the last calculated route for you but it will tell you it has lost that connectivity and it won't update the route for those outside factors. Nor will it recalculate if you leave the planned route, as all planning is done at the mothership. I have a route I use it for fairly frequently and there is a 20 minute stretch with no cell service, so Waze complains for that 20 minutes. Once back in coverage, sometimes it automatically connects, sometimes it seems to have given up and won't connect unless I stop it and restart it. I suspect Apple and Google maps work the same way.

    The on-device navigation systems are, as it sounds, on the device and can be used with zero external connectivity. Of course, if you want traffic, or dynamic routing around accidents, incidents, construction zones, etc., you will need some sort of connectivity. So when Sygic, for example, offers traffic updates, it is assuming you have that connectivity. No connectivity, no avoidance navigation.

    So which is better? Depends. On-demand requires connectivity for just about everything. Although the "local" map may be on your device because that was the last one you used, if you use On-demand and want to go someplace new, particularly if it's far away, those maps for that route will need to be downloaded for you. But the advantage is that you get the absolutely latest information, including traffic delays, in near real time. On-device has the advantage of working without any connectivity at all, but you have to dedicate storage for the maps you *might* use, even if you aren't using them very often. Right now, I have an on-device navigation system called CoPilot GPS with all the maps for North America (US, Mexico, Canada) and it takes 3.61GB of storage. I also have Waze and it is reporting 108 Mbytes, or about 3% of what CoPilot is using.

    As for accuracy, GPS for cars is accurate to about 5 meters (16.5 feet). That's good enough to use on the road as most of the system use a feature called "snap to road" that assumes you are ON the road, even if the most recent fix is not. Theoretically it is possible to have accuracy to within millimeters, if you want to step up in price to a dedicated GPS system. (Think Google Maps and Apple Maps cars driving around. I suspect they have a more accurate GPS to get the maps as accurate as they can.) (Geologists also track movements of the earth along earthquake faults using high-accuracy GPS receivers.) Cell tower triangulation can help get a bit more accuracy, which is why you see that nag notice if you turn off cellular and just use GPS. The improvement with cell triangulation is to about 5 feet, which is handy in cities where the bouncing signals from GPS can make it less accurate. I suspect 5G will enhance that triangulation, but I haven't seen any figures on it.

    GPS is degraded if the satellite "constellation" above you is out of optimum shape. When a satellite gets low in the sky the bending of the signal through the atmosphere can make a few nanoseconds worth of error. (A nanosecond of error is just under 1 foot, so a delay of 15 nanoseconds would give you an additional 15 feet of error, for a total of 30 feet of error.) Bounce is even worse as every foot of added distance for the signal in the bounce degrades your position by that same foot. That's why GPS wanders around in cities as the signals bounce all over the place. Recent launches of additional satellites has significantly reduced the "bad constellation" instances and the logic in the calculations says, basically, "5 of us agree we are HERE and you single satellite vote THERE. We will use HERE."

    Some systems will let you view the GPS data as it comes in. "Back in the day" you could actually see the constellation of satellites being used for the fix, so you could judge for yourself the accuracy. I haven't done that in years--no need for it with all the satellites that are currently up.

    If you want more boring tech details, PM me. No need to bore the rest of the visitors to the forum!

    EDIT: Added a bit of clarity on Waze navigation being done on the mothership.
    That was a very helpful summary of how the different systems work. I guess I assumed some of that - my RV has a built-in navigation unit so it works everywhere without any external signal, but it knows nothing about traffic conditions - but it is always good to get confirmation and much of what you posted I did not know. Thank you for taking the time.

    As far as getting a used iPhone without a SIM card for the nav system, I ordered that this afternoon and it should be here in a couple of days. Iended up ordering an iPhone 6 with 64GB since I could not find one with 32GB. We have a trip scheduled early next week so I should know how the whole thing works relatively soon. I expect to add Waze, Google Maps and Sygic and its maps to the iPhone and see how they work. Sygic offers real time traffic information, but it is apparently an add-on and I have not checked how much extra it costs.

    Interestingly enough we have an old Garmin hand-held gps unit that we used to use for hiking and it had the satellite display that you referred to and it was easy to see how many satellites the device was referencing. All of that seems to be gone.

    One of the puzzling things to me is why these nav systems do not show elevation. Our old portable system - a Rand McNally - showed elevation but Waze does not and neither does Google Maps. I don't know about Sygic because I really have not used it, but I expect to on our next trip.

    Thanks again for all of the information.

  4. #34
    iPhone as a wifi device
    MacInWin's Avatar
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    One of the puzzling things to me is why these nav systems do not show elevation. Our old portable system - a Rand McNally - showed elevation but Waze does not and neither does Google Maps. I don't know about Sygic because I really have not used it, but I expect to on our next trip.
    Elevation is not critical to road navigation and it adds a lot of extra data to have 3D maps. All the terrain information has to be added to the lat/lon info already there for 2D. That extra data adds about 50% to the size of the files with the maps. In addition, altitude is the most unreliable aspect of GPS. The challenge is that all of the satellites are on one side of you (above you) so there is a natural bias in the calculations. By the time a satellite is low on the horizon and useful for altitude, the error induced by the signals travelling through a lot more atmosphere makes them more unreliable overall. It's a lot better now than it was in the "early days" when you could be at the beach, literally at sea level and have the GPS report anywhere from +500 to -500 feet.

    I used to have a 3D mapping system. I don't remember the name, but the map sizes were huge. It was kind of cool to be driving up a valley and see the hills on either side on the screen, but to be honest, the terrain information just wasn't useful for road navigation.

    EDIT: If the system you use has a screen to show lat/lon, it should also show elevation. But again, the maps are 2D for the most part.
    Jake

  5. #35
    iPhone as a wifi device

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    I am sure that what you have written is absolutely correct, but I am not particularly interested in terrain mapping. We travel in an RV and that means that part of our decision as to where to stop for the night depends upon the local temperatures - can we sleep in the heat or will it freeze - and that often depends upon the elevation. Where we live, in southern Arizona, we need to be above 5000 feet to have a decent chance of sleeping at night during the summer and the same is true for neighboring states like New Mexico and Nevada, so the elevation is important to us.

    Navigation systems get gps signals and the position of those satellites is known by the system. It seems a relatively simple thing mathematically to compute the elevation based on the angles of the satellites and both our hand-help Garmin (which is so old it no longer works) and our old Rand McNally portable nav system gave us elevation but our Sync 3 nav system from Ford (which is built into our RV) and the one from Chrysler built into our Jeep do not do so. Neither do Wave or Google Maps, at least as far as I can tell from my limited use of them, and that means that I end up having to use an app for my phone, and as simple as the computation should be I just don't see why the nav systems don't provide it.

    I am sure you are right about the elevation data for terrain mapping, but I would be perfectly happy with gps computed elevations.

  6. #36
    iPhone as a wifi device
    MacInWin's Avatar
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    Let me recommend some solutions, all of which, I think, are in the App Store from your iPhone:

    Inrix Traffic - brilliant for traffic, navigation is OK
    MotionX-GPS - recording tracks, elevations, speeds
    Altimeter+ - Yep, just what it says

    There are a lot of options in the App Store. Those are my three I have kept.

    EDIT: Again, the road mapper software typically used for navigation while driving is not dependent on altitude as the maps are flat. You have a specific need for altitude, and it's perfectly available from GPS, but the map software makers choose not to have altitude (or the terrain modeling routines) in their software. If you do a search at the App Store for 3d map gps you can see what is available (not much for roads, but pretty good options for hiking, biking, skiing).
    Last edited by MacInWin; 08-09-2019 at 10:02 AM.
    Jake

  7. #37
    iPhone as a wifi device

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    Thank you for the list. I will check them out.

    I do wonder if any of them are compatible with CarPlay as I do not wish to use the small screen of the phone. The whole idea is to get the apps to work through my Sync 3 system using the larger screen of the vehicle entertainment display. I know that Waze, Google Maps, Apple Maps and Sygic are compatible, but don't know about the others.

  8. #38
    iPhone as a wifi device
    pm-r's Avatar
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    I know that Waze, Google Maps, Apple Maps and Sygic are compatible,...

    Would something like this help:
    How to Find Elevation on Google Maps on iPhone or iPad
    How to Find Elevation on Google Maps on iPhone or iPad: 7 Steps



    - Patrick
    ======

  9. #39
    iPhone as a wifi device

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    Quote Originally Posted by pm-r View Post
    Would something like this help:
    How to Find Elevation on Google Maps on iPhone or iPad
    How to Find Elevation on Google Maps on iPhone or iPad: 7 Steps
    This might work in the hilly areas, but does not seem to do much in the flat areas.

    I checked Google Maps for our home, followed the steps and was told that we were at an elevation of 100 feet. We are, in fact, about 1500 feet above sea level, but probably 100 feet over the lowest flat land in our area.

    What would be nice is just an entry on the map display that indicated the elevation.

  10. #40
    iPhone as a wifi device
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    What would be nice is just an entry on the map display that indicated the elevation.

    OK, how about Google Earth.app???
    Measure distance & elevation - Google Earth Help

    or
    Google Earth Hacks: How to Find the Elevation of Any Point On Earth
    YouTube




    - Patrick
    ======

  11. #41
    iPhone as a wifi device
    MacInWin's Avatar
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    Quote Originally Posted by MikeFromMesa View Post
    Thank you for the list. I will check them out.

    I do wonder if any of them are compatible with CarPlay as I do not wish to use the small screen of the phone. The whole idea is to get the apps to work through my Sync 3 system using the larger screen of the vehicle entertainment display. I know that Waze, Google Maps, Apple Maps and Sygic are compatible, but don't know about the others.
    I don't use CarPlay (I don't have a compatible system) but I seem to have read somewhere that you can be doing other things on the iPhone and still have maps, etc, sent to CarPlay. If that is the case, run Sygic through Car Play, bring up Altimeter, or MotionX on the iPhone.
    Jake

  12. #42
    iPhone as a wifi device
    Slydude's Avatar
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    Quote Originally Posted by MacInWin View Post
    I don't use CarPlay (I don't have a compatible system) but I seem to have read somewhere that you can be doing other things on the iPhone and still have maps, etc, sent to CarPlay. If that is the case, run Sygic through Car Play, bring up Altimeter, or MotionX on the iPhone.
    That is true although I can't say whether it is true for all apps. I've only had a CarPlay capable system for a few months and don't use it every day but you can have one app on the car screen and something different on the phone screen simultaneously. I've had Maps and Safari open simultaneously as well as Apple Maps and Google Maps simultaneously.
    “Hard work beats talent when talent fails to work hard.”
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