If you worried about the internal gps in the ipad, I suggest looking at a clip on "badelf gps" or something similar, always handy to have 2 gps sources in the cockpit if something goes tits up.
Ben West Oz -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Mike Borgelt Sent: Tuesday, 12 March 2013 10:12 AM To: Discussion of issues relating to Soaring in Australia. Subject: Re: [Aus-soaring] Apple - gliding At 11:43 AM 12/03/2013, you wrote: >On 12/03/2013, at 11:57 AM, Dave Long & Cath Lincoln ><[email protected]> wrote: > > > Hi Emilis, > > > > I suspect that the GPS unit in the iPad is not as sophisticated as > > those we are used to using in aviation. > >GPS is GPS. There hasn't been a huge amount of "sophistication" for >most of the last 20 years. Except for SA getting turned off in 2000 and the boys and girls running their system have learned how to tweak their satellite clocks for accuracy and later Block satellites being launched with higher power transmitters. The algorithms in GPS receivers have also been greatly improved. With some early ones you needed a time or an approximate position to initialise the receiver. No longer required as most modern GPS modules will find themselves in 45 seconds from a cold start. Also more sensitive front ends and parallel processing internally, not sequential and far greater number of correlators. If the thing has a window in a room it is likely to find itself. There is also the issue of receiver optimisation for the dynamics of the vehicle it is in. With advanced modules it is possible to select maximum accelerations etc for various classes of vehicles and also any averaging or dead reckoning times. Put something in an aircraft that was optimised for pedestrians, boats, cars etc and you may see some anomalies under some conditions. I suspect the GPS in the iPad isn't aviation optimised. Try turning off the wifi and 3G or LTE connection on the iPad and see what happens when flying. Glonass is being rejuvenated, there's a Chinese system and the European Galileo. In the next few years I think most "GPS" receivers will use all available satellites/systems. You can buy high end receivers that do this already. BTW GPS can give you 3 D velocities straight from the doppler shifts accurate to mm per second. It isn't done by differencing the positions. Mike >You're probably actually seeing the opposite. The GPS in most mobile >devices, regardless of vendor, is deployed on the understanding that >it'll spend quite a lot of its life indoors, where it'll be virtually >impossible to get a satellite lock. > >So it's an "assisted" GPS. It uses last known GPS position, >triangulation with visible 3G towers, and observations of which >geolocated WiFi base stations are in range to provide additional >fidelity, which is why it does a pretty good job of showing where you >are even when you're inside a building, and can provide a location >almost immediately instead of waiting for satellites like your panel >mounted GPS does when you turn it on. > >Then the compromises set in: the device designers subsequently figure >that since they can supplement poor GPS reception with other data, they >didn't need to pay as much attention to the GPS antenna. So the device >has one which is smaller, lighter, more physically constrained than a "real" >GPS device. > >In built up areas you don't notice the compromise, because even though >the GPS isn't necessarily receiving a great signal, there are plenty of >other location cues and you still get accuracy to within a handful of metres. > >But travel out into the middle of nowhere, shield the already >compromised GPS receiver under a few layers of FRP, and take yourself >50 km from their nearest 3G base station and 200km from the nearest >WiFi and the antenna limitations become obvious. > >Different vendors will suffer to different extents, but none of them >get off scott free in this respect. > > - mark > > > >_______________________________________________ >Aus-soaring mailing list >[email protected] >To check or change subscription details, visit: >http://lists.internode.on.net/mailman/listinfo/aus-soaring _______________________________________________ Aus-soaring mailing list [email protected] To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring _______________________________________________ Aus-soaring mailing list [email protected] To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
