hich is usually a differential data signal from a standard fixed location with known coordinates, received via wifi (that’s why the iPhone tells you it can locate you more precisely with the Wifi on).
I don’t think so 
The wifi is used to get a rough fix, based on IP location. It produces a faster time to fix, not a more accurate fix.
What is damn annoying is that e.g. the camera app on new Samsungs (android v6) refuses to save the geolocation unless the wifi bit is enabled. That in turn can result in saving imprecise coordinates in the EXIF. In v5 you could choose “GPS or nothing”.
you definitely need an aviation grade GPS device
I reckon a rooftop antenna is the biggest single thing in reliability. I have had very poor results with getting EGNOS with a handheld GPS. However EGNOS will still not help with the geoid correction. You get lateral only.
And even the latest £550 phone (S7) still have the old 160ft altitude error, whereas every IFR GPS has the geoid correction.
But this can be solved with android because there are NMEA bluetooth GPSs which take an external (rooftop) antenna. I have been flying with one for 14 years.
I agree, an exterrnal antenna helps a lot. Not for IR though, but I guess that’s out of the question anyway for most people :)
stevelup wrote:
Try changing to SkyDemon 2 chart format where things look as you would expect. Or turn off the ‘trees’ layer.
I thought it might have to do with the chart style, so I tried to change from “SIA” to “Skydemon 1”. But since it didn’t help, I didn’t try “Skydemon 2”… Turning off the tree layer does indeed help also with the SIA chart style.
EuroFlyer wrote:
It doesn’t really matter what the resolution of the terrain is, the gps receiver also needs to know exactly where it is. Talking about tablets, that is.
Excellent point. Strange that no one thought about that Still, you cannot de couple the accuracy from the velocity. 15m (the accuracy) is travelled in 0.3 s at 100 knots. The accuracy of a GPS is way more than necessary for VFR. The altitude is another thing. My Nexus X has a barometer. I can chose if I want to use GPS alt or baro alt. I think SD and EVFR exclusively use GPS alt, but I’m not entirely sure. In some of those GPS test apps, this can be chosen. The barometric accuracy is probably not much to brag about, but it is there, and could be configured as a backup.
The second thing is mobile connection. I remember the first Google maps on phones used GSM to find location. It worked surprisingly well. All phones use AGPS today, so the accuracy is much better than 15m. More importantly, the position is not dependent of GPS. It is as you say 15 m 95% of the time, but probably at least 100m 99.9 % of the time (just as an example). The chances of losing all position data is miniscule. If SD and similar take advantage of this, I don’t know, probably not?
Google maps and other map apps do indeed take advantage of all the data available to them. The best backup may very well be a phone with Google maps. Also, there are lots of apps with detailed 10m or better terrain.
Zero-zero takeoff and landing using SV (synthetic vision)
Done with a Socata TB30!
I think the information from the garmin 3d view is accurate and repeatable, and actually easier than a visual landing thanks to the 3d cg track vector (the round aiming point that projects the actual cg track, different from the plane 3d heading which is also shown, but not used correctly in the video). The difficult part (when visual flying becomes again much easier than 3d view) is just before the flare, since I doubt the gps or altimeter are accurate enough. A radar altimeter would be better to judge altitude above the runway. Personally I’ve flown approached with 3d view many times, but never below 300ft agl for the above reason.
I knew someone who used to do zero-zero landings in an SR22, so this is not new.
By hand? I tried “autolanding” a C172 with a GFC700 once (with appropriate supervision, in a safe setup, legally, etc) and it worked quite well. Off the centerline but definitely survivable.
As it has come up several times recently, I´d like to start a discussion on this.
Obviously synthetic vision as it is available on most EFIS platforms like Aspen or Gramin have the idea of improving flight safety and to give an additional mean to safe the day in case of emergency. But how good are they really?
So how is your experience, particularly in critical approaches such as in the mountains? Are the representations of terrain accurate enough to stay out of trouble i.e. in an emergency when you loose visual references unexpectedly?
Screenshots and other things are appreciated.
The SV depiction on the G1000 platform is very good and accurate, but that’s not the issue at hand here. Critical terrain (-1000 to -100 ft below is shaded yellow, -100 or above shaded red) is depicted very nicely.
I think the problem is that a pilot tends to be overwhelmed quickly (voice alert “terrain terrain”, sv and terrain display pop up warnings etc..). Then there is a sensory overload and the information isn’t realized and processed as it hasn’t been used in any training scenario. There is simply too much stuff depicted on a SV display for the human brain to make a viable decision. I don’t know of any airliners that use SV displays. EGWPS is dead simple, with a soft “terrain, terrain” and a hard “whoop whoop, pull up” aural alert – probably because studies have shown that any more information will not get processed anyway.
The next problem is, if a pilot has maneuvered himself too deep into a terrain problem, the airplane may not have enough power to escape from terrain, even it is shown on the SV display. Unless it’s a powerful turbine or a fighter jet, “pull up” isn’t going to work any wonders.
SV looks cool, if it’s really a viable tool, I don’t know! It would need dedicated training to fly using the SV display.
Now with automatic emergency landing available in some planes, maybe an automatic terrain avoidance feature will be next. And soon we can all order a drone via an app and save us the hassle of flying at all, it’s a circle jerk :)
