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(free) gps2tas iphone app

dhall_polo

Well Known Member
GPS2TAS:
http://itunes.apple.com/us/app/gps2tas/id381224165?mt=8

I was inspired by some recent threads from brantel and others to do some additional checks of my airspeed indication. I wasn't quite hitting vans numbers, and I was so sure I'd built a clean plane. After doing the calcs, it looks like my indicators are low, and I'm right on vans numbers. Now my next step is to fiddle with my safeair static port to see if I can increase accuracy. Anyway, there's a lot of great info in the forums about computing TAS from GPS track information, and I was able to find spreadsheets and online tools that can do the computations for you. I guess I'm impatient and didn't want to wait until I landed to get the TAS results, so what the heck, I decided to write iphone app number cajillion and one.

If you want to see how accurate your airspeed indicators are, just download this app (free) and bring it with you. It works just like the spreadsheets and online tools, requiring you to fly three legs and input your heading and groundspeeds. Once it has valid vectors, it computes TAS on the fly. It currently requires an iphone with the new v4 os. I'll upload a version that supports the older 3.x os when I can.

In putting the app together, all credit for the math goes to fellow RV'er, Doug Gray. I was able to reference algorithms published by Doug more than a dozen years ago, located here: http://www.kilohotel.com/rv8/rvlinks...y/TAS_FNL4.pdf. Additional references are available on the NTPS site here, which also leverages Doug's work as the base. Here's a post that sums it the general topic of computing TAS from GPS data. Most of the links in that post are now invalid, but it's a start. If you have any issues, questions, or comments, please feel free to PM me.
 
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I happened to have a little "free aviating" time this afternoon, so I downloaded this and took it along - works great! Both the TAS and computed winds compared very well to those same values computed on my EFIS. It must be a great App - it told me that my airspeed error is still less than 1 knot. ;)
 
OK, this app had better be worth the effort, guys. I just spent the last few hours downloading iOS4 for my 3GS, just so I could try this app! If it's no good, then I'M NOT PAYING! :D
 
Yeah, iOS4 on my 3G iPhone is so slow I feel like bouncing it off the pavement.

I did download your app and plan on using it soon. Thanks for contributing to the community.
 
Went to download the App to try it out on my way to AirVenture. I have not updated to OS4 and refuse to do so till after AirVenture. The App requires OS4 so looks like I will have to wait till after I get home from AirVenture to be able to download and try it.

I updated to the latest Apple iPhone OS last year before going to OSH. My phone kept crashing and needed to reboot to get it working again. I do not want this happening again so will not be doing any UPDATES to my iPhone till at least the next month. After hearing so many people say how OS4 is slow, I am not sure I even want to try it. I have the 2nd generation iPhone or the first model to have 3G service that is not the 3GS model.
 
references on gps2tas

I was asked a question or two about the calculations. Most of the links in the post I referenced initially are bad now. Here's some detail.

Credit for the math goes to a fellow RV'er, Doug Gray, from down under. He published an article back in 1998. See:
http://www.kilohotel.com/rv8/rvlinks...y/TAS_FNL4.pdf

Another good source is this one. They have some additional formulas and information on calculating TAS with more than 3 legs. This site also references Doug's original work.
http://www.cockpitgps.com/other_articles/GPS_TAS/calibrating_a_compass_and_calcul.htm

Finally, it's not surprising that Ken has a detailed reference on the subject:
http://go.phpwebhosting.com/~khorton/rv8/phplinks/index.php?&PID=49

That ought to be enough to get someone going on a droid app. Isn't "droid" just some sort of code word for "I wish I had an iphone."? :)

Good Luck!
 
Isn't "droid" just some sort of code word for "I wish I had an iphone."? :)

Good Luck!

LOL!...Hey I'll have you know that I owed one of the first PDA's ever. It was an Apple circa 1991 or so. I forget what they called it. I know what I called it... a piece of... Then I went to a IIci and onto a Powerbook. At the time peripherals were 3 or 4 times more expensive. So I switched to PC's. Hated computers ever since, boy they sure are cheap though :)

Yeah, I am not a fan of Droid much either, but I am just a slave to Sprint.
 
I have the 2nd generation iPhone or the first model to have 3G service that is not the 3GS model.
Stay miles away from ios4 on this phone. Upgrade to the i4 and it will run just fine. If you are still running a 2nd gen 3G (as I was until 2 weeks ago) you should be no-cost-upgrade-eligible.

Oh yeah, great app too.
 
The App requires OS4 so looks like I will have to wait till after I get home from AirVenture to be able to download and try it. [snip] I have the 2nd generation iPhone or the first model to have 3G service that is not the 3GS model.

Not to detract from how cool it is that this neat little app has been written, but if you have an iPhone 3G, my strong recommendation is do NOT upgrade to iOS4. It's simply not worth the pain. My 3G stalls for up to 10 seconds at a time... I'll be downgrading back to iOS3 and will live with that until the inevitable hardware upgrade down the track... [edit] Jeff, what is this magical "no cost upgrade" of which you speak? US only, I'm guessing :-(
 
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So, being a bit of a junkie for speed testing, and having a Ram-mounted iPhone cradle in the plane...Don's app sounds great.

Hearing Condor's story of OSH phone nightmares, and Jeff's os warning, I'm wondering: is my one year old 3G one of the ones to avoid ios4 with?

I'm a bit version-challenged, as evidenced by the fact I bought a 3G one month before the 3GS came out (not a peep from them at the time of course! :mad:) Any thoughts on os management are most appreciated.

Not sure at 1 year post-purchase, that I'd be able to get the no cost phone upgrade, unless you know something I don't (a very likely scenario! :D). Will call ATT tomorrow, but from the smarter gadget guys...should I leave the 3G alone till the ios4 bugs get ironed out, or just wait till I can get a 4, and just use Kevin's spreadsheets till then?

I do want to be able to get in touch with the gang at OSH and provide vectors and progressive taxi instructions to our ice chest in Sleepy Hollow (hopefully somewhere near you Don...I've asked Pam), so I'm heeding Condor's warning till after the show! But a new toy...very inviting! ;)

Cheers,
Bob
 
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Bob,

You are correct- avoid upgrading to ios4 on your phone. You should contact AT&T (or look on their website) to check your upgrade eligibility for the new iphone 4, as they moved up the "get a new iphone without paying the early termination fee" date as part of the iphone 4 release. That was the "no cost upgrade" that I in-artfully mentioned before. My wife is in the same boat as you, bought a 3G a month before the 3GS came out, and she is eligible for upgrade.

AT&T's service at OSH '09 was abysmal, party because they got hit with a double whammy of not only the load on their normal network from all the smartphones, but they handled the wifi on the grounds. EAA has promised much better service this year- it literally couldn't get much worse.

@OP- sorry for the thread creep, but this is relevant info for anyone who wants to update their OS to be able to use your handy little app.
 
Great app and simple to use, thank you

I downloaded it last night and since I had never calibrated my airspeed, decided to check it out.

Fist test showed that my TAS was off by around 4-5 knots at cruise speed, then I calibrated my TAS on GRT and after tested again. The second test was off by 1 knot, I guess close enough.
 
ios3 support

I posted a version that doesn't require ios4. It takes a few days for apple to review and release. Check back in a few. Given past performance from apple in review apps, it might not be posted till next wed.

I have ios4 on my 3gs. I don't have any problems with slowness, but I do have major battery life issues. Frankly, there are a lot of issues with ios4, and I wouldn't recommend anyone upgrade until after a few patch releases have come out. I know there are many people with 3gs and ios4 with no issues, but the forums are filled with people having issues.

Went to download the App to try it out on my way to AirVenture. I have not updated to OS4 and refuse to do so till after AirVenture. The App requires OS4 so looks like I will have to wait till after I get home from AirVenture to be able to download and try it.

I updated to the latest Apple iPhone OS last year before going to OSH. My phone kept crashing and needed to reboot to get it working again. I do not want this happening again so will not be doing any UPDATES to my iPhone till at least the next month. After hearing so many people say how OS4 is slow, I am not sure I even want to try it. I have the 2nd generation iPhone or the first model to have 3G service that is not the 3GS model.
 
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Jeff, Don and others: Thanks much for the info!

Jeff, checked, and sure enough, I'm eligible, and ATT will let me spend my $$ for a 4. :)

Of course, no ATT store, Apple store or Best Buy in town has them...gotta be ordered.

So it'll be OSH on my 3G with no ios4 (safest route to keep comms open at the show for vectors to and from the beer wagons...mine included, and $200 extra for gee-dunk at OSH!!) I'll get Don's app when it comes out in the 3G compatible version (checked today and it was the 4-only version still. Will get it and test it and report back when I do Don...thanks!)

One clarification on the hold-fire recommendation on ios4 Don: Is that just for (not getting) ios4 on a 3G/GS, or are you also recommending holding off on an iPhone4 till the first few patches are in? I know that piece is not really RV related, but it is a cockpit tool, so what the heck, figured I'd ask.

Thanks again!

Cheers,
Bob
 
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One clarification on the hold-fire recommendation on ios4 Don: Is that just for (not getting) ios4 on a 3G/GS, or are you also recommending holding off on an iPhone4 till the first few patches are in? I know that piece is not really RV related, but it is a cockpit tool, so what the heck, figured I'd ask.


You don't have a choice with the new phone, it comes with the new os.

bob
 
FWIW, after successfully upgrading my 3Gs with iOS4, I've noticed no degradation in speed. Everything appears normal to me.

While flying today, I decided to try out your app. Flew the headings, input the ground speeds and <voila'> my TAS was 163kts. My EFIS was reading steady at 160kts, so it apparently reads 3 knots slower than I'm really going.

Thanks for the cool app, Don!
 
Great app

I had a chance to try out this app yesterday and it worked great.

FWIW, I have the new OS4 on my 3GS and haven't noticed any difference in performance since OS3. I am curious to find out about the free upgrade though.
 
You don't have a choice with the new phone, it comes with the new os.

bob

Bob,

Roger that...what I meant to ask is, was Don recommending not only waiting to upgrade a 3G to ios4, but also waiting to get an iPhone4 at all until after some patches are in for ios4...not sure if the issues (which appear to be intermittant and not universal, but would certainly find me :rolleyes:) are also hitting the 4. Was just asking before I drop the bucks on the 4.

snip...I am curious to find out about the free upgrade though.

I think free in this context meant no early termination fee, as long as you're in the "upgrade window"...phone still costs money (dern it! ;))...biz as usual...except it appears the upgrade window has been expanded due to the rapid advances in products...and perhaps to keep the hoardes of semi-recent 3G/3GS buyers from screaming too loud.

I was in Best Buy looking for a couple other items, and mentioned to a phone guy there that I may be upgrading to the 4. He jumped on that, and pulled up my ATT account, and said I was eligible (later confirmed by ATT). Best Buy guy (admittedly not the best source of data) said as long as you're within a year of upgrade eligibility (time left on contract), you can upgrade. He quoted $199 for a 16 gig and $299 for a 32 gig, with no rebate needed to get that price. He mentioned that ATT might get you to that price with a mail-in rebate, but I have yet to confirm that, since no stores here have them. Not quite free, but at least there are options for upgrading.

To keep it thread-related, just looked again for the 3G version of gps2tas, but its not in the store yet. No worries...just interested to see how it compares to the NTPS sheets, which show my TAS readout is 2-5 knots fast (1-2%, at max speed) over several different speed mod test runs (avg +3). It'll be fun to see!

Cheers,
Bob
 
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3G != 3GS

Just to avoid any confusion - a 3G (first 3G iPhone) is not the same as a 3GS (which came out later, with the compass etc). As I understand it, a 3GS runs iOS4 reasonably happily. 3G, not so much.
 
Just to avoid any confusion - a 3G (first 3G iPhone) is not the same as a 3GS (which came out later, with the compass etc). As I understand it, a 3GS runs iOS4 reasonably happily. 3G, not so much.

That's been my experience for the past few days - my IT guys upgraded mine as a matter of course, and it seems to be running just fine. I am definitely not a power user though - I have it because they give it to me....
 
Just to avoid any confusion - a 3G (first 3G iPhone) is not the same as a 3GS (which came out later, with the compass etc). As I understand it, a 3GS runs iOS4 reasonably happily. 3G, not so much.

That's been my experience for the past few days - my IT guys upgraded mine as a matter of course, and it seems to be running just fine. I am definitely not a power user though - I have it because they give it to me....

Roger all, and thanks! I'll just apply the "if it ain't broke" theorum to the phone till after OSH, so comms will remain up!

Oh, and I asked the Best Buy guy if he had an OSH special on the phone...he just looked at me like I had a horn growing out of my forehead! :p Think ATT or Apple will have a booth there? ;)

Cheers,
Bob
 
Why not take it to the logical conclusion - CAS?

All you need to get to CAS is to convert TAS using pressure altitude and OAT, assuming they are equally accurate. There is a page on each of my spreadsheets on the left side of the page for that.
 
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