What a difference 7 years makes

[ArtVandelay]

Apple uses something they call “assisted GPS”. A non-assisted GPS requires a few minutes to scan and sync up all the GPS satellites unless your in the same location when you powered off. For those with GPS watches or handheld GPS devices will notice this.
Apple is about the user experience and didn’t want them waiting so they chose to link it with the cellular function.

[toto]

5 hours ago, Vance Harral said:

People have what I think is a mistaken impression that the GPS receiver and the cellular radio in iPads are two separate components, and that Apple chooses to remove both of them in less expensive models for marketing reasons.  It's more likely they're integrated in a single IC (even though they can be independently powered on or off), and that the architecture therefore doesn't support removing one without the other.  The following link claims to be a block diagram of an older model iPad.  While I can't confirm it's genuine, if it is accurate, it shows the GPS receiver and cellular radio as a single unit: https://datasheetgadget.files.wordpress.com/2014/10/ipad-3.png.

I don't expect anyone to take my word as gospel.  Apple doesn't publicize detailed block diagrams of their hardware, and I'm just guessing.  But having spent nearly three decades in the computer hardware industry, I can attest that what consumers sometimes see as a dirty, back-room sales and marketing tactic, is often just an engineering decision based on available components and practical integration constraints.  I'm inclined to believe Apple doesn't offer a WiFi-only iPad with GPS simply because it's too much trouble architecturally.  All modern cellular transceiver chips have integrated GPS, so you get a GPS receiver for free when you commit to cellular.  Leaving that component entirely out of the design is one thing.  Designing and manufacturing a variant that replaces that integrated cellular/GPS receiver with a standalone GPS chip would likely be a much bigger hassle.

Yep, it’s my understanding that the GPS and cellular radio are integrated into the same component. Whether it would be possible for Apple to produce an iPad with one or the other, I have no idea - but other manufacturers separate the two functions, and offer a GPS in their wifi-only tablets. The end result is that iPad consumers have to buy a cellular radio they don’t want, or go without a GPS that they do want. 

Apple is a hugely successful company, and I have no doubt that they make very good decisions - both for customer satisfaction and for their bottom line. They are famously unapologetic for design decisions that seem confounding at a glance, but later become a standard that other companies emulate. 

Anyway, I’m not trying to suggest that the GPS+cellular thing is wrong in any absolute sense. It’s just an annoyance for me to have to buy a thing that I don’t want in order to get another thing that I do want. Feels like cable tv all over again. And as carusoam pointed out, in order to buy the GPS, you have to buy another thing that requires a monthly subscription. So the cellular function is just battery-draining dead weight if you don’t pay the subscription fee. 

[ArtVandelay]

Anyway, I’m not trying to suggest that the GPS+cellular thing is wrong in any absolute sense. It’s just an annoyance for me to have to buy a thing that I don’t want in order to get another thing that I do want. Feels like cable tv all over again. And as carusoam pointed out, in order to buy the GPS, you have to buy another thing that requires a monthly subscription. So the cellular function is just battery-draining dead weight if you don’t pay the subscription fee. 

You don’t need to sign up for cellular data, so no subscription fee necessarily.

[toto]

3 hours ago, ArtVandelay said:

Apple uses something they call “assisted GPS”. A non-assisted GPS requires a few minutes to scan and sync up all the GPS satellites unless your in the same location when you powered off. For those with GPS watches or handheld GPS devices will notice this.
Apple is about the user experience and didn’t want them waiting so they chose to link it with the cellular function.

Yep, that’s right. They do use AGPS, but they don’t require that the cellular function be turned on in order to use location services. The cellular function on my iPad is turned off 99% of the time.

Seriously, if I’m flying around with the cellular function turned on, my battery life is much much worse than with just location services. And that’s with a barely-used iPad that’s less than a year old. 

[toto]

1 minute ago, ArtVandelay said:

You don’t need to sign up for cellular data, so no subscription fee necessarily.

Right, I’m just saying that if you don’t pay for it, then it gives you no value at all. So you either buy the thing you don’t want that is theoretically useful (which is what I’ve got now), or you buy the thing you don’t want that can’t be used (which is what you’ve got if you don’t pay the subscription fee). 

[toto]

8 hours ago, donkaye said:

Filing IFR flight plans and getting preflight briefings in the middle of nowhere requires the cellular iPad.

Yep, this is the one case where I occasionally turn on the cellular function. Getting a briefing or filing a flight plan in the middle of nowhere.

I’ve actually had surprisingly good luck with rural FBOs that have functioning wifi, but a cellular iPad definitely gives you more options.

[McMooney]

29 minutes ago, toto said:

Yep, this is the one case where I occasionally turn on the cellular function. Getting a briefing or filing a flight plan in the middle of nowhere.

I’ve actually had surprisingly good luck with rural FBOs that have functioning wifi, but a cellular iPad definitely gives you more options.

Exactly how I use my IPad, it's the utility of that cell connection that does it for me.   I flight plan, file, brief, weather, adsb, etc...   when i'm at my destination, i call ubers, web browse, check weather, chat with people, etc...   I have a  GDL393d for adsb and position.

I also have a Samsung S7 tablet which is my preferred in plane device ( screen, brightness, Pen ) but mainly due to it's size and lack of cell, only gets pulled out on longer trips.

None of these actually beats my high-end office depot  notebook and pen/pencil combo for writing things down.  I can absolutely use the s7 tablet for this purpose but man that pen and paper combo is soooo hard to beat.

[DCarlton]

2 hours ago, toto said:

Yep, that’s right. They do use AGPS, but they don’t require that the cellular function be turned on in order to use location services. The cellular function on my iPad is turned off 99% of the time.

Seriously, if I’m flying around with the cellular function turned on, my battery life is much much worse than with just location services. And that’s with a barely-used iPad that’s less than a year old. 

So... if the cellular service is off, the iPad is in a receive only mode of some sort.  Is it receiving GPS over a separate GPS antenna and RF interface, or is receiving the GPS position information somehow over the cellular RF interface (in receive only mode)?  In that case, I'm assuming the cellular system is triangulating somehow.  [Is the cellular RF interface completely separate from the GPS RF interface at different freqs using different protocols].  

[Hank]

11 hours ago, cliffy said:

Could the GPS requirement for cellular be because the cell phone uses GPS to locate and triangulate for best cell tower connection OR so YOU can be tracked in your every move down to single digit distances?  :-) 

No, it's entirely an Apple marketing gimmick to con people into paying more. Samsung includes GPS on all of their tablets, including wifi-only models selling for ~$150. But ForeFlight is only available in iOs, not android. So I use my cheap Samsung Galaxy Tab tablet, wifi model with functioning GPS [bought on sale for $109 early this year], and Avare [sectionals, WACs, TACs, enroutes, approach plates, airport diagrams--all free and all georeferenced; the approach plate changes automatically to the airport diagram while I am rolling out on the runway].

[cliffy]

6 minutes ago, Hank said:

No, it's entirely an Apple marketing gimmick to con people into paying more. Samsung includes GPS on all of their tablets, including wifi-only models selling for ~$150. But ForeFlight is only available in iOs, not android. So I use my cheap Samsung Galaxy Tab tablet, wifi model with functioning GPS [bought on sale for $109 early this year], and Avare [sectionals, WACs, TACs, enroutes, approach plates, airport diagrams--all free and all georeferenced; the approach plate changes automatically to the airport diagram while I am rolling out on the runway].

I used Avare on my androids for years ( I was a very early adopter) but switched to IFlyGPS this year after OSH because  "we" (the wife) like the interface better. 

For  a completely free  system for charts and flying Avare really is hard to beat. 

[Skates97]

59 minutes ago, cliffy said:

I used Avare on my androids for years ( I was a very early adopter) but switched to IFlyGPS this year after OSH because  "we" (the wife) like the interface better. 

For  a completely free  system for charts and flying Avare really is hard to beat. 

I've been using iFlyGPS for a couple years now. I previously used DroidEFB but I like the interface and features of iFlyGPS more so will be sticking with it.

[Wayne Cease]

I set the iPad (current one is the latest iPad Air) on my left thigh, kneeboard goes on my right thigh (right handed). The kneeboard holds a piece of paper, a dorm I created on Word, that holds frequency numbers for the airports on my flight, plus lots of room to write down my IFR release, ATIS, frequency changes during the flight. The paper is a regular 8x11 folded in half with the form on both sides.

Having all the frequencies written down is helpful to make sure I got them right, and really helpful on an out-and-back flight as I use them in reverse.

I bought a case with a strap for the prior iPad, but only used it a few times. The iPad sits on my lap easily without moving.

This set-up works fine in my SR22. Not sure how well it would work with a yoke instead of the side stick.



Wayne

[0TreeLemur]

48 minutes ago, Wayne Cease said:

I set the iPad (current one is the latest iPad Air) on my left thigh, kneeboard goes on my right thigh (right handed). The kneeboard holds a piece of paper, a dorm I created on Word, that holds frequency numbers for the airports on my flight, plus lots of room to write down my IFR release, ATIS, frequency changes during the flight. The paper is a regular 8x11 folded in half with the form on both sides.

Having all the frequencies written down is helpful to make sure I got them right, and really helpful on an out-and-back flight as I use them in reverse.

I bought a case with a strap for the prior iPad, but only used it a few times. The iPad sits on my lap easily without moving.

This set-up works fine in my SR22. Not sure how well it would work with a yoke instead of the side stick.



Wayne

 

Would not work in a Mooney with manual gear.   Nothing strapped to right thigh.  I mounted iPad to panel and keep kneeboard on left thigh in our manual-gear C.

[Hank]

9 minutes ago, 0TreeLemur said:

Would not work in a Mooney with manual gear.   Nothing strapped to right thigh.  I mounted iPad to panel and keep kneeboard on left thigh in our manual-gear C.

I strap my kneeboard to my left leg in my electric gear Mooney (also righthanded) to keep it from hitting / rubbing on the throttle quadrant. That also allows room for my checklist to fold open (written in Word, printed landscape in booklet format, laminated, folded in half and stitched into a booklet).

When I remember to bring my tablet, and don't load it in the back with the luggage, I stick it somewhere but don't have a regular location, and nothing that wi stand up to turbulence. 

[KB4]

21 hours ago, donkaye said:

After watching a student try unsuccessfully to write a clearance with the Apple Pencil, I chose not to buy one.  I keep a record of every flight whether it is a flight with a student or a flight of mine alone.  I keep a paper copy of them and have found myself going back to review them periodically to confirm either a date of some other factor.

For every flight of mine I record at a minimum, the Date, Start time (from the GTN 650), Air time (from the MVP-50), fuel used (MVP-50 read directly without computation needed), the Ending Tach Time (from the MVP-50), From Location, To Location, if an IFR flight, the Clearance and any Amendments.

Apple Pencil with the pro is good. Always charged. Well worth getting.  If having issues writing usually means need new tip on the pencil.  

[cliffy]

On 9/29/2021 at 8:03 AM, ArtVandelay said:

I’m waiting for one of the old timers on MS tell us how paper charts and a clipboard and pencil are better, still get their briefings via phone and you don’t need fancy avionics.

Me Me Me 

Other than an electronic "SECTIONAL" (could even be paper) what does someone need more of to fly VFR anywhere in the country? IFR different story but VFR? I can go Utah to FL on just a Sectional chart and most of the time its not necessary to talk with anyone. A NORDO J-3 can do Ii.  All the other stuff is fluff when it comes right down to it.  :-) 

[EricJ]

14 hours ago, DCarlton said:

So... if the cellular service is off, the iPad is in a receive only mode of some sort.  Is it receiving GPS over a separate GPS antenna and RF interface, or is receiving the GPS position information somehow over the cellular RF interface (in receive only mode)?  In that case, I'm assuming the cellular system is triangulating somehow.  [Is the cellular RF interface completely separate from the GPS RF interface at different freqs using different protocols].  

GPS is in different frequency spectrum than cellular services, and wants an antenna with a beam shape pointing mostly up, so its antenna and rf tuner and radio interface will always be different and separate from the cellular receiver.  There are other reasons that they are kept separate, but these are reason enough by themselves.  A cellular system can provide rough geolocation very quickly, more quickly than waiting for the GPS system to acquire a sufficient number of satellite signals to refine a position from scratch.   The cellular system does this by knowing the direction and coverage area of the cellular base station antenna your signal is being received in, and by a ranging protocol that all cell systems use to improve efficiency (works like DME).   That quickly provides a rough geolocation, that the GPS system can then use to know which satellites should be overhead, because they are tightly scheduled, and focus on acquiring those specific satellites rather than just waiting to figure out what satellites of all the possible satellites are currently in view and then slowly start to refine position as they are gradually acquired and identified.

The rough geolocation provided by the cellular system is not adequate to determine exactly where you are, but definitely good enough to significantly accelerate GPS lock.   Once the GPS fix is acquired, that can be shared with the cellular system to provide a much more highly refined geolocation.

Edited October 1, 2021 by EricJ

[Skates97]

19 hours ago, 0TreeLemur said:

Would not work in a Mooney with manual gear.   Nothing strapped to right thigh.  I mounted iPad to panel and keep kneeboard on left thigh in our manual-gear C.

Maybe it depends on the size of the kneeboard? I have manual gear and have always had my kneeboard strapped to my right thigh, never any problems swinging the Johnson bar. I do sometimes have to wake my wife up and get her to sit up straight so she isn't in the way after an in-flight nap, but that's a different story. 

[0TreeLemur]

1 hour ago, Skates97 said:

Maybe it depends on the size of the kneeboard? I have manual gear and have always had my kneeboard strapped to my right thigh, never any problems swinging the Johnson bar. I do sometimes have to wake my wife up and get her to sit up straight so she isn't in the way after an in-flight nap, but that's a different story. 

And the size of the butt relative to the seat too, I suppose.   With my build I wish the Mooney front seat had 1" more width.   I could have it on my right leg it, but the kneeboard is just nicely out of the way on the left.

[DCarlton]

13 hours ago, EricJ said:

GPS is in different frequency spectrum than cellular services, and wants an antenna with a beam shape pointing mostly up, so its antenna and rf tuner and radio interface will always be different and separate from the cellular receiver.  There are other reasons that they are kept separate, but these are reason enough by themselves.  A cellular system can provide rough geolocation very quickly, more quickly than waiting for the GPS system to acquire a sufficient number of satellite signals to refine a position from scratch.   The cellular system does this by knowing the direction and coverage area of the cellular base station antenna your signal is being received in, and by a ranging protocol that all cell systems use to improve efficiency (works like DME).   That quickly provides a rough geolocation, that the GPS system can then use to know which satellites should be overhead, because they are tightly scheduled, and focus on acquiring those specific satellites rather than just waiting to figure out what satellites of all the possible satellites are currently in view and then slowly start to refine position as they are gradually acquired and identified.

The rough geolocation provided by the cellular system is not adequate to determine exactly where you are, but definitely good enough to significantly accelerate GPS lock.   Once the GPS fix is acquired, that can be shared with the cellular system to provide a much more highly refined geolocation.

So then what I find interesting is that the iPad is able to effectively acquire the GPS satellites using a GPS antenna embedded in the iPad when it's inside the airplane.  If I'm understanding correctly.  

Or... is the IPAD using the rougher cellular geolocation to keep your position on the moving map updated when it can't receive GPS.  

Tough discussion to have going back and forth.  Interesting though.  Thanks.  

[EricJ]

42 minutes ago, DCarlton said:

So then what I find interesting is that the iPad is able to effectively acquire the GPS satellites using a GPS antenna embedded in the iPad when it's inside the airplane.  If I'm understanding correctly.  

Or... is the IPAD using the rougher cellular geolocation to keep your position on the moving map updated when it can't receive GPS.  

Tough discussion to have going back and forth.  Interesting though.  Thanks.  

Yes, the gps antenna(s) inside the tablet or a cell phone or stratux or G5 or whatever are usually sufficient to receive the signal inside the airplane.   Due to some shadowing from the cabin structure, it may miss one or more satellites that it could otherwise receive if it were outside in the open, but since it isn't shadowed by trees or mountains or buildings, it otherwise has a pretty good shot at getting enough to get a fix.    I was configuring the new G5 in my airplane inside the airplane inside my hangar with the door open, without the supplemental external antenna, and it was showing reception of multiple satellites just using its internal antenna.

 

[Vance Harral]

4 hours ago, DCarlton said:

So then what I find interesting is that the iPad is able to effectively acquire the GPS satellites using a GPS antenna embedded in the iPad when it's inside the airplane.  If I'm understanding correctly.

One thing that makes this confusing is that "acquisition" is a complex concept when it comes to GPS receivers.  Acquisition doesn't just mean receiving electromagnetic energy from the satellites via the antenna in the iPad/G5/whatever.  That happens more or less instantly, and is a function only of the antenna itself.

However, the receiver must go through a complex startup sequence once it sees electromagnetic energy, to search around a doppler-shifted frequency space, determining individual satellites' PRN codes, etc, before it can establish an initial position fix (see Wikipedia for a brief introduction).  This takes a while if the receiver must perform a from-scratch search.  It turns out you can speed up the process considerably if the receiver already has a general, gross idea of where it is.  One way of doing that is to assume you're in about the same place, at about the same time, as when you last powered down the receiver.  Most (all modern) GPS receivers have this capability, which is why your car - and airplane - get a rapid GPS fix after a brief stop at the fuel pump.  If you don't drive/fly for a couple of weeks, though, acquisition time is slower.

At some point during the integration of GPS into phones and tablets, somebody realized that time and location information from cell towers was a great starting point for GPS acquisition.  That's what "AGPS" is: an acquisition algorithm that leverages cell tower data to achieve a rapid initial solution, even if the device has been powered down a long time, and/or moved from the location where it was powered down.

All this acquisition stuff only takes place at power up.  Once an initial position fix is established, the device constantly tracks the satellites it's receiving, and adjusts lock frequencies, etc as necessary.  The location and time it last powered down, and whether it can see cell towers, becomes irrelevant.  Well, except in the event you actually lose lock and have to start over.  But that's pretty rare these days.

So going back to the iPad-in-an-airplane scenario: you hop in your airplane, and power up your iPad at exactly the same time you power up your panel-mount navigator.  The iPad is probably going to get an initial fix first, because it leverages AGPS; while the panel mount device has to make do with guessing it's in the same place/time it was at power-down.  This arguably makes the iPad a superior device.  By the time you're rolling for takeoff, though, both devices are tracking.  At that point, your panel-mount navigator is an arguably better, because its antenna has a clear view of the sky, while your iPad receiver is somewhat obstructed by cabin structure.  In practice, though, it hardly matters.  Your panel-mount is nearly always going to get a solution before you even release the brakes to taxi (unless maybe you shut down the airplane three months ago and shipped it to the other side of the world).  And as mentioned above, modern GPS antennas and receivers are so good that it hardly matters whether the antenna is in the cabin or not.

[Will.iam]

I had the ipad 2 using it as a curiosity when flying across the atlantic back in 2009. The internal gps was not good enough to get a position at altitude (35000-39000ft) so i jailbroke the ipad to get around the apple proprietary bluetooth stack and installed bluetooth device drivers that would connect to any standard bluetooth device. I  used an external gps that had a 10 times per second update rate and would last for 40 hours per rechargeable user replaceable battery for $30! The bad elf at the time was $200 and only had an 8 hour battery life which was not long enough on some of our 10 hour flights and would take up to 15 mins to get a position if it was not turned on before takeoff. Something about moving 800ft per second on a 1 position update per second gps was hard for the device to acquire a position. My gps with 10 position updates per second would get a fix no later than 45 seconds at altitude and usually acquired a fix in 5 seconds.
one time that ipad highlighted an INS failure on #1 INS as our position on my ipad was drifting further and further away from our planned track. On further investigation not only had INS 1 failed but the FMS was not comparing the INS 2 & 3 to INS 1 or it would have ignored INS 1 instead of following it and showing INS 2 &. 3 as drifting. I was glad we had an independent source to show INS 1 was truly the faulty INS.

Now with the new ipad 11 it will acquire a  position at altitude most of the time but there are those days it just will not lock still vastly improved  acquiring the gps fix than in the past. I’m not sure if that is all apple’s credit though as the gos satellites have been getting slowly replaced with newer satellites with more powerful beams that allow your receiver to pickup a signal in areas that just a few years ago was impossible.   It does way better if you get the position on the ground before you takeoff as it’s easier for the ipad to keep the position once it’s already has a fix. 
I’ve never had the ipad not lock in my mooney so i think it might be the slower speeds of the mooney help or the fact i always have my ipad on before i takeoff. 

[carusoam]

We have come a long way since the iPad 1 days…

Trying to run WingX on the ground in the back of a commercial flight had its challenges…

Getting reception through the jets tiny windows…

Keeping connected as the Jet sped up…

Reconnecting after the GPS signal was lost…

It is really extra challenging to hold an iPad up to the window in full display of everyone onboard… after they ask that all electronic devices be turned off and stowed…  

 

PP’s old memory only…

Best regards,

-a-

[LANCECASPER]

6 hours ago, Will.iam said:

I had the ipad 2 using it as a curiosity when flying across the atlantic back in 2009. The internal gps was not good enough to get a position at altitude (35000-39000ft) so i jailbroke the ipad to get around the apple proprietary bluetooth stack and installed bluetooth device drivers that would connect to any standard bluetooth device. I  used an external gps that had a 10 times per second update rate and would last for 40 hours per rechargeable user replaceable battery for $30! The bad elf at the time was $200 and only had an 8 hour battery life which was not long enough on some of our 10 hour flights and would take up to 15 mins to get a position if it was not turned on before takeoff. Something about moving 800ft per second on a 1 position update per second gps was hard for the device to acquire a position. My gps with 10 position updates per second would get a fix no later than 45 seconds at altitude and usually acquired a fix in 5 seconds.
one time that ipad highlighted an INS failure on #1 INS as our position on my ipad was drifting further and further away from our planned track. On further investigation not only had INS 1 failed but the FMS was not comparing the INS 2 & 3 to INS 1 or it would have ignored INS 1 instead of following it and showing INS 2 &. 3 as drifting. I was glad we had an independent source to show INS 1 was truly the faulty INS.

Now with the new ipad 11 it will acquire a  position at altitude most of the time but there are those days it just will not lock still vastly improved  acquiring the gps fix than in the past. I’m not sure if that is all apple’s credit though as the gos satellites have been getting slowly replaced with newer satellites with more powerful beams that allow your receiver to pickup a signal in areas that just a few years ago was impossible.   It does way better if you get the position on the ground before you takeoff as it’s easier for the ipad to keep the position once it’s already has a fix. 
I’ve never had the ipad not lock in my mooney so i think it might be the slower speeds of the mooney help or the fact i always have my ipad on before i takeoff. 

I don't doubt your story about the INS failure and the iPad 2 coming in handy, however I'm sure it wasn't in 2009 since the iPad 1 wasn't announced until January 27 2010 (https://www.apple.com/newsroom/2010/01/27Apple-Launches-iPad/) and wasn't released until April 3, 2010.