For those who do are not yet fully convinced, despite my assertions in many posts (¹), Here's another example of the accuracy of iPad GPS, cut off from any cellular or terrestrial Wi-Fi network. Already lived in 2011 during a stay in La Reunion (²), this time back from a recent trip to London I brought back the "proofs" below, screenshoted aboard an Airbus A320 :
On board an Airbus A320 window seat, with Airplane Mode enabled
You can see, among other things, that Vertical Position Error (EVP) is less than Horizontal Position Error (HPE), which proves, once again, the dreaded accuracy of Chipsets GPS contained in these devices. I would like to point out that the airplane mode activated does not cut GPS reception.
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(¹) iPhone built-in GPS : a formidable accuracy !
Crossing the Pacific with an iPad
Crossing the Atlantic with an iPad
aso.
(²) I am writing from Bourbon Island
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Regarding GPS accuracy, Apple never answered the question of whether the chip incorporated WAAS/EGNOS corrections, what the good old Garmin GPS72 portable or the Furuno GP37 does for example. This is an essential component of location accuracy. The famous Bad Elf external GPS receiver for tablets without GPS incorporates well, itself, WAAS/EGNOS/SBAS/MSAS corrections.
A recent thesis allows us to compare the precision of our entry-level GPS with professional GPS
http://dumas.ccsd.cnrs.fr/docs/00/93/84/70/PDF/GHEHENNEC_Romain.pdf
During the same measurement campaign on board a ship, 95% Furuno measurements (with EGNOS) are better than 3,5 meters, while the comparable values for professional equipment range from 1 down to 2 meters.
As for the precision indicated (HPE and VPE), there is reason to think that this is the theoretical precision, calculated solely from the distribution of satellites in the sky given by the ephemeris, and not the real precision which depends on the number of satellites actually received. We see in fact that this precision does not change when we place the tablet in a place where reception is poor., like in a room in a house where an ordinary GPS receives nothing.
For additional information, some interesting links :
The state of Qualcomm’s modems
Smartphones, Tablets and GPS Accuracy
Qualcomm Collaborates … to Employ BeiDou for Location-Based Mobile Data
Completely convinced, I was able to check the value of the iPad Air's GPS between the Canaries and Lyon on board an A320. It's impressive.
How to change the altitude displayed in feet, in meters in iNavX ? I can't find.
Sincerely
Bernard
Setting Units : Decimal distance in meters
L’évolution des chipset GPS est énorme. J’arrive à capter plus de satellites sur mon Samsung Android qu’avec le GPS fixe Furuno sur mon voilier avec une antenne externe. Une remarque: la Vertical Position Error est faible et pratiquement sans conséquence à 85OO mètres, mais au niveau de l’eau c’est autre chose. Les GPS s’appuient sur une référence moyenne de hauteur d’eau et sur l’hypothèse que la terre est parfaitement ronde. In both cases, à faible altitude, c’est faux.
You are absolutely right, je n’utiliserai pas mon iPhone pour un atterrisage en parapente dans le brouillard. Ni pour estimer la hauteur des vagues 😉
Voilà un moyen bien pratique pour mesurer précisément son tirant d’air 😉
Oui, but at 5,8 m near, it might pose a problem getting under the bridge!