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GPS App or Garmin GPS??
  
 
rw11
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p.2 #1 · p.2 #1 · GPS App or Garmin GPS??


dsjtecserv wrote:
Not had a problem in the west either. Any ideas of where it can be a problem?

Dave


In valleys and canyons, deep forest, etc. Anything that can block satellites - as per my comments above and they poster on the raft trips.

Newer phones are better (usually). My iPhone 6 does a much better job than my old iPhone 4 did (and I've used them at the same exact spots).

Also, GPS in my iPhone 6 is better than in the D5300 Nikon body I have just to use for geolocated photos...

My pet peeve is the lack of GPS in cameras...



Sep 08, 2017 at 07:31 PM
dsjtecserv
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p.2 #2 · p.2 #2 · GPS App or Garmin GPS??


rw11 wrote:
In valleys and canyons, deep forest, etc. Anything that can block satellites - as per my comments above and they poster on the raft trips.

Newer phones are better (usually). My iPhone 6 does a much better job than my old iPhone 4 did (and I've used them at the same exact spots).

Also, GPS in my iPhone 6 is better than in the D5300 Nikon body I have just to use for geolocated photos...

My pet peeve is the lack of GPS in cameras...


OK. I concur on the potential effect of canyons, although even there I have not had problems of any lasting significance. Never had an issue in forests.

But I was referring to your statement:

"This makes sense because they block some of the satellite signals."

Which implies that "they" (government authority?) is somehow actively blocking GPS signals in some particular locations. There was no other reference to who or what "they" is. Were you meaning to refer to canyons?

Incidentally, canyons are not unknown in the east, and they don't exactly cover most territory in the west. So I still believe that phone-based GPS, without the need for a cell or wifi signal, is a viable method of backcountry navigation. Exceptional places that topographically inhibit signals will have the same effect on dedicated GPS devices, so that isn't a reason to prefer dedicated units over phones. That was the what the original poster was inquiring about.

Dave



Sep 08, 2017 at 08:08 PM
rw11
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p.2 #3 · p.2 #3 · GPS App or Garmin GPS??


actually the govt. does "block" some signals - i.e. the military gets much higher precision than civilians do

(and no - even if you are doing work for the Army on a base they have, they will not allow use of that precision - ask me how I know..)

but I meant canyons, valleys, dense forest

I think most posters should try their phones and see



Sep 08, 2017 at 11:14 PM
dsjtecserv
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p.2 #4 · p.2 #4 · GPS App or Garmin GPS??


Yes, I'm aware that civilian-use signal are lower resolution than those used by the military. But there doesn't seem to be any evidence that all GPS signals are being actively blocked over a wide area (or perhaps any area). Topography may have a local effect, but that is not different for dedicated GPS versus phones, the topic of this thread.

I agree, members should be encouraged to try using their phones, and not be discouraged by some of the misleading information that was unfortunately posted earlier.

Dave



Sep 08, 2017 at 11:51 PM
cambyses
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p.2 #5 · p.2 #5 · GPS App or Garmin GPS??


rw11 wrote:
actually the govt. does "block" some signals - i.e. the military gets much higher precision than civilians do

(and no - even if you are doing work for the Army on a base they have, they will not allow use of that precision - ask me how I know..)



Not really. The govt. no longer "blocks" any signals. There used to be the so-called "Selective Availability (SA)" which intentionally degraded accuracy for civilian receivers. But by using the so-called Differential GPS, civilian receivers could eliminate it, and so by President Clinton's order, SA finally got turned off on May 1st, 2000. Currently there is still the L2 signal that is modulated by the longer P(Y) code which can only be tracked by military receivers, whereas most civilian receivers only track L1 signal modulated by the shorter C/A code. However, there are ways for the civilian receivers to get around that, and still achieve centimeter-level accuracy (and surveying GPS receivers have been doing that for many years). What distinguishes military receivers at this point is not really their accuracy, rather their robustness, and in particular, their anti-jamming capability. That being said, gps receivers in smartphones, and even PND's like Garmin, etc. are mostly limited by their poor antenna performance as well as their susceptibility to multipath in non-open-space environments (e.g., urban canyon) which can severely degrade their accuracy. But the accuracy even in smartphones will further improve in future as more advanced gps receivers get integrated. Trust me on that. since, if you have a flagship smartphone from any major vendor, there is a good chance I was involved in the design of the gps receiver chip in your phone.




Sep 09, 2017 at 12:19 AM
rw11
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p.2 #6 · p.2 #6 · GPS App or Garmin GPS??


by get around the L2 issue do you mean receive it or some other work around?


Sep 09, 2017 at 01:13 AM
GroovyGeek
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p.2 #7 · p.2 #7 · GPS App or Garmin GPS??


There is only one reason to buy a dedicated GPS unit these days - if you are worried about robustness. On a phone you get a much larger screen, much nicer UI, and once you pay for an app free topo downloads most anywhere in the world. All for under $20 on top of a phone you already own.

I actually bought a Moto Turbo 2 with a giant 35000mAh battery and a shatter proof screen from CL for around $150. Put it in a water-proof case for another $10 and now I have a super robust GPS that kicks any Garmin/Delorme/etc unit in the nuts any time of day or night, for at most half the price. I personally prefer Backcountry Navigator over Gaia by a large margin, but I seem to be in the minority. Both have demos to try before you buy.

Dustin Gent wrote:
so here is what you do when using ANY GPS app on an iphone/Android. Turn on the airplane mode, turn on location services.

That used to not be possible on an iPhone some time ago, the moment you turned on airplane mode the GPS went off, and you could not run GPS without the radio being on. Was kinda stupid, have they fixed that? When I am out for more than a day I will usually carry a 8000mAh USB battery. Sufficient to recharge the phone 2x and last about a week even with fairly active use. Still print topos out of Caltopo from sheer paranoia though.



Sep 09, 2017 at 03:00 AM
 

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dsjtecserv
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p.2 #8 · p.2 #8 · GPS App or Garmin GPS??


Nothing I saw with Gaia convinced me to switch from BCNav. It has some quirks but once you know them it will take you were you need to go. the XE version now on Kickstarter looks interesting, but I'm not sure it adds enough to switch to a subscription plan. Most people would find the paid version of BCNav more than adequate.

Dave



Sep 09, 2017 at 03:28 AM
cambyses
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p.2 #9 · p.2 #9 · GPS App or Garmin GPS??


rw11 wrote:
by get around the L2 issue do you mean receive it or some other work around?


The key benefit of using dual frequency is to be able to eliminate the ionospheric error which is frequency-dependent. Now with current L2 signals, civilian receivers can still use some so-called code-less techniques (e.g. Z-tracking, code-aided squaring, etc) to essentially get L2 measurements for ionospheric error estimation without knowing/tracking P(Y) code.

In addition, a new civilian signal has been added to L2 (called L2C) though it is still in pre-operational stages and not all satellites support it.

Finally there is also the new civilian signal at the lower L5 band that the civilian receivers can track to achieve better accuracy (thanks to both ionospheric error estimation as well as better code orrelation properties on the L5 signal).

All that said, adding the support for a second frequency means additional receiver complexity, higher power consumption, and ultimately higher cost. And, cost and power consumption are very critical in the smartphone space (unlike, say, surveying receivers). As such, the key question is when the major OEM's will view dual-freq advantages as significant-enough to justify the added complexity and cost.




Sep 09, 2017 at 04:16 AM
rw11
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p.2 #10 · p.2 #10 · GPS App or Garmin GPS??


Thx - one more question: any ideas on why cameras have such poor GPS (when it is built in)?


Sep 09, 2017 at 06:00 PM
Dustin Gent
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p.2 #11 · p.2 #11 · GPS App or Garmin GPS??


rw11 wrote:
Thx - one more question: any ideas on why cameras have such poor GPS (when it is built in)?


probably they use a much more cost "effective" lower sensitivity receiver, and probably doesn't use GLONASS. my buddy has an old magellan (they still in business?) GPS, and that thing is horrible by today standards.



Sep 09, 2017 at 06:57 PM
Dustin Gent
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p.2 #12 · p.2 #12 · GPS App or Garmin GPS??


Dustin Gent wrote:
so here is what you do when using ANY GPS app on an iphone/Android. Turn on the airplane mode, turn on location services.

GroovyGeek wrote:
That used to not be possible on an iPhone some time ago, the moment you turned on airplane mode the GPS went off, and you could not run GPS without the radio being on. Was kinda stupid, have they fixed that? When I am out for more than a day I will usually carry a 8000mAh USB battery. Sufficient to recharge the phone 2x and last about a week even with fairly active use. Still print topos out of Caltopo from sheer paranoia though.


i used the earthmate on a Samsung Note 4 and 5 and new iPhone. i don't when they started putting in GPS receivers in phones, but they are MUCH better than just 4 years ago!

paper maps and compass are STILL the way to go



Sep 09, 2017 at 07:00 PM
cambyses
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p.2 #13 · p.2 #13 · GPS App or Garmin GPS??


rw11 wrote:
Thx - one more question: any ideas on why cameras have such poor GPS (when it is built in)?


The GPS receivers in today's smartphones support multiple constellations (GPS, GLONASS, etc) and have already gone through many cycles of performance optimization with more advanced signal tracking, multipath mitigation, better navigation algorithms, etc. And they also leverage the cellular network to get assistance data (thus the so-called A-GPS) which helps them with faster signal acquisition. The cameras, on the other hand, use basic GPS receivers with basic algorithms and obviously with no network assistance.




Sep 09, 2017 at 08:13 PM
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