Welcome, Guest. Please login or register.

Login with username, password and session length
Forums Search:  


Author Topic: iPhone track interval?  (Read 3473 times)

terrypin

  • Jr. Member
  • **
  • Posts: 5
  • Karma: 0
    • View Profile
iPhone track interval?
« on: August 30, 2016, 12:38:24 PM »
There has been an enormous increase in the number of trackpoints that my iPhone 6S+ is recording for recent walks. I haven't pinned down the cause yet. Could be some mistake of mine, a setting or whatever, although I'm darned if I can see any on the iPhone.

Here is a selection of results:



--
Terry, East Grinstead, UK

Boyd

  • Expert Advisor
  • *****
  • Posts: 3849
  • Karma: 43
    • View Profile
Re: iPhone track interval?
« Reply #1 on: August 30, 2016, 08:20:21 PM »
Might help if you told us what app you are using. ;)

terrypin

  • Jr. Member
  • **
  • Posts: 5
  • Karma: 0
    • View Profile
Re: iPhone track interval?
« Reply #2 on: August 31, 2016, 12:10:47 AM »
Thanks, fair point. On the assumption that there are 'iPhone GPS' users here, I was trying to keep it crisp, but I guess a little more background would have been helpful!  ;)

I use the Memory Map app on the iPhone to record the GPS data. So far I've found no way of altering the rate of this data capture, unlike many dedicated GPS devices and perhaps smartphones. As you see from the more recent examples (red in my table) every GPS change is recorded, with a typical interval as brief as 2-3 seconds. Leading to very close points and therefore a large total number of them.

An exactly flat walk of even as little as one minute could result in a good estimate of distance, say 250 ft. But, because altitude estimates by GPS are very inaccurate, even for dedicated devices, it would give a highly misleading estimate of gross ascent and descent, maybe over 100 ft a minute on my iPhone 6S+!


After transfer of the GPS file to my PC I open it in the desktop Memory Map application to display and work on it. From there I can save in the universal GPX format for work in other progtams, such as Google earth, GPS Utility, etc.

Naturally, I've emailed Memory Map too.

--
Terry, East Grinstead, UK

Boyd

  • Expert Advisor
  • *****
  • Posts: 3849
  • Karma: 43
    • View Profile
Re: iPhone track interval?
« Reply #3 on: August 31, 2016, 05:07:31 AM »
Sorry, not familiar with Memory Map. I use two apps mosly, Galileo and Map Plus. Galileo has two settings that affect track recording,  Accuracy Threshold and Distance Threshold. Map Plus has three similar settings, Accuracy Desired, Minimum Interval and Minimum Distance. I have seen similar settings in other apps.

Basically the idea is that you can discard points if you don't have a good GPS fix and you can choose how often to record points based on either how far you have moved or a fixed time interval.

If Memory Map doesn't have similar settings then perhaps there's no way to control track recording?

terrypin

  • Jr. Member
  • **
  • Posts: 5
  • Karma: 0
    • View Profile
Re: iPhone track interval?
« Reply #4 on: September 02, 2016, 03:57:11 AM »
Thanks Boyd, helpful feedback.

I'm also finding that the iPhone seems poorer at recoding signals than it was.

I've simplified my illustration of the high rate of trackpoints:



Reckon there's something wrong with iOS 9.3.4, although it's still possible the fault lies with Mem-Map.

--
Terry, East Grinstead, UK





Boyd

  • Expert Advisor
  • *****
  • Posts: 3849
  • Karma: 43
    • View Profile
Re: iPhone track interval?
« Reply #5 on: September 02, 2016, 04:47:09 AM »
FWIW, I also have a 6s+ (and love it). Haven't recorded any tracks recently so I wouldn't have noted a change. You could try using a couple other apps as a test, there should be some free ones. That might give you an idea whether it is a problem with Memory Map or iOS.

BTW, the current version of iOS is 9.3.5 and it contains important security updates, so you might want to install it.

But,I don't think you are on the right website to get help with this. This forum is mainly intended to support the maps that are hosted here, and they are all in Garmin's proprietary format. I'm probably the only one that uses and iPhone here.  ;)

terrypin

  • Jr. Member
  • **
  • Posts: 5
  • Karma: 0
    • View Profile
Re: iPhone track interval?
« Reply #6 on: September 04, 2016, 06:13:21 AM »
Thanks Boyd, appreciate the feedback - particularly the heads up about wrong forum!

I've also posted in another GPS forum, a GPS newsgroup, and a coupel of iPhone/iPad forums.

Love my 6S+ too (updated to 9.3.5 yesterday), but a major use is GPS recording, so anxious to sort this.

--
Terry, East Grinstead, UK

Boyd

  • Expert Advisor
  • *****
  • Posts: 3849
  • Karma: 43
    • View Profile
Re: iPhone track interval?
« Reply #7 on: September 04, 2016, 09:20:13 AM »
If accuracy is important to you, check out the Garmin GLO which is a small device that connects to your phone with bluetooth. Did some testing last year and wrote this: http://forums.gpsreview.net/discussion/30108/what-is-gps-accuracy-testing-the-garmin-glo-in-the-forest

terrypin

  • Jr. Member
  • **
  • Posts: 5
  • Karma: 0
    • View Profile
Re: iPhone track interval?
« Reply #8 on: September 05, 2016, 02:14:45 AM »
Very interesting thread, thanks.

I'll take a look at the GLO but
1. Over recent years I've become increasingly committed to the 'one device for all purposes' camp. Even leaving my Canon IXUS 220 HS at home now.
2. Even walks (hikes) of 10-12 miles, at leisurely pace with frequent stops, often discharge the iPhone 6S+. Bluetooth is a heavy power consumer. What's your practical experience?

--------------------

I saw your comment in that linked thread about the iPhone capturing several trackpoints per second. I'm fairly sure I recall reading elsewhere that the rate was "1 per sec". Can't find my source now.

That apart, what do think about my tenative conclusions earlier that accuracy decreases as trackpoint rate increases? Not only altitude (which I've almost given up on) but distance too, albeit to a lesser degree?

--
Terry Pinnell, East Grinstead, UK

Boyd

  • Expert Advisor
  • *****
  • Posts: 3849
  • Karma: 43
    • View Profile
Re: iPhone track interval?
« Reply #9 on: September 05, 2016, 06:12:34 AM »
I believe the iPhone internal GPS only records one point per second. This is pretty typical for most devices, including Garmin's dedicated handhelds. The GLO is unusual in that it provides 10 position updates per second. They have positioned it as an aviation device, and an airplane can travel pretty far in a second. ;) But from what I saw, the iPhone could not read all 10 updates per second, IIRC, I was getting something like 6 or 7.

Yeah, probably not the best solution for long hikes, I think it is more useful if you want to accurately map something. I just don't go on long hikes anymore, so not too concerned about battery life. Of course, you can get some pretty nice waterproof/shockproof cases that include a battery though.

I also like the one device for everything approach, which is why I don't use my Garmin Montana 600, Nikon DSLR or Sony XDCAM-EX much these days. But each of these devices do offer unique advantages over a phone and I'm glad I have them. :)

 

anything