Thursday, May 24, 2012

iPhone Avy Beacon App: The Joke's On You

Three years ago, an April Fool's post on an iPhone avalanche beacon app was clever enough to fool readers into thinking it was real -- or was it that some readers weren't clever enough to detect an obvious joke?

Either way, the joke is now on us, or at least on anyone who buys the SnoWhere app for anything other than $9.99 worth of amusement.  (This came out much earlier in the year, but I was reminded of it recently with the introduction of the slickly marketed and attractively priced "snow-be" -- or make that, "find-me" but don't count on me finding you!)

I'm all for a radical rethinking of the dated beacon spec (ETSI EN 300 718-1, 718-2, 718-3), and indeed Barryvox (along with its licensee ARVA) has been doing just that with its W-Link secondary frequency on the Pulse beacon, and Pieps is slated to do that with its GPS-equipped Vector.  I've also been impressed by all the various functions my phone can perform, some originally intended by the designers, and other cleverly designed by third parties.

Designing an app to allow one phone to locate another phone buried underneath the snow would be a great university course project, thereby following up on apps that can find a lost or stolen phone, or an errant child.  But, "SnoWhere Could Help Save Your Life"?  No.

A phone is incapable on transmitting or receiving on the standard 457 kHz avalanche beacon frequency.  But if both the victim and the would-be-rescuer had phone with compatible apps, could one phone somehow search for another phone?  Sure, the victim's phone could acquire GPS signals, and that information could be transmitted to the searcher's phone.

So in theory, yes, but in reality, here are all (or at least some of?) the potential problems (even assuming that both the victim and searcher both have the app running):
  1. Dependence upon a satellite network.  This should be okay though, since the GPS satellite network is reliable.  Plus other types of rescue devices depend upon satellite networks (e.g., GEOSAR for PLBs, Globalstar and GPS for Spot).  
  2. GPS signal acquisition underneath snow.  A high-sensitivity GPS receiver with an antenna optimized for GPS signal reception can indeed acquire GPS signals underneath snow.  But phones typically lack the very latest in GPS chips, and their antennas are optimized for cell phone networks, not GPS satellites.  SnoWhere claims, "In our tests, the best GPS location accuracy was +/-5m on iPhones 4 & 4S and +/-10m on iPhones 3G & 3GS."  Even setting aside how rigorous these tests were, that means that the very best scenario is that SnoWhere will leave the searcher with an area to probe of 845 or 3382 square feet (4/4s and 3G/3GS, respectively).  And how knows how much that degrades under whatever more demanding scenarios that SnoWhere did not test.
  3. Bluetooth transmission underneath snow and over long distances.  The very latest iPhone has Bluetooth 4.0, and earlier versions listed as compatible with SnoWhere have Bluetooth 2.0 or 2.1 -- yet SnoWhere only vaguely claims that, "SnoWhere has a range of 40m and has been tested in depths up to 2m." without specifying which model(s).  Somewhat anecdotally, my Droid Incredible has Bluetooth 2.1 with a headset range of only a few meters before static overwhelms with the voice quality.  If SnoWhere's vague claim of 40m-range indeed degrades under certain conditions, and if SnoWhere's 10m-accuracy claim for the iPhone 3G/3GS also degrades under certain conditions, the span over which SnoWhere provides any useful information might approach zero (e.g., 25m Bluetooth range coupled with 20m GPS accuracy).
  4. WiFi interference.  Remember to turn off WiFi beforehand or else "performance" (such as it is) is even further degraded.
  5. Phone call interference?  The following passage implies that if a phone call is randomly received during the search, then SnoWhere will shut down entirely:  "SnoWhere also remembers when you might forget – by restarting automatically after phone call interruptions to keep you transmitting, so your friends can find you. You’ll always know that SnoWhere is running by its reassuring ping."
  6. Search interface.  The "video" shows only a few static screen captures and never shows video of a phone actually homing in on a victim.  Does it even have any directional indicators based on the searcher's GPS location?  Or does it just show a map (whose details will be worthless over such a short distance involved in a rescue) and then the searcher has to figure out which way to go?
  7. Manipulation of your phone's touchscreen with bare fingers in cold temperatures while in a panic.  No need to elaborate here.
The bottomline?  The very bottom of the website's main page provides this disclaimer:
"No location device can offer a guarantee that you will be found: SnoWhere is no exception."
I agree with the first part, but not the second part:  SnoWhere is indeed an exception, as it pretty much guarantees that a fully buried victim will not be found quickly enough to prevent asphyxiation.


  1. Another argument: water in the atmosphere (clouds) or water on the ground (snow) can cause GPS reflections thus degrading fix accuracy. I've noticed this to be especially pronounced during big storms and in bowls and chutes on my Android device.

  2. Yes, although I put a link in at item #2 to a detailed article on GPS performance under snow, that was for for dedicated GPS receivers with high-sensitivity chips. I suspect that those conditions would greatly degrade a phone's accuracy (which under optimal conditions isn't good enough to narrow down the probing area anyway to a reasonable section).
    Let's just hope that this app is withdrawn from the market or used only for entertainment value, since rescue would be pretty much impossible with it...

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