Hi all,
I’ve posted this on another forum also but thought I’d solicit some wider views / opinions with an issue I’m currently experiencing with my iPad.
Device is an iPad Mini 5 cellular with built in GPS running the latest IOS running the latest version of SkyDemon.
In summary immediately after takeoff and close to the ground I get very erratic GPS performance which can be seen in the following Skydemon track log. From the track log the altitude is bouncing around quite a bit and the location is equally erratic and a little bit off. It behaves this way when closer to the ground but as I climb it sorts itself out and becomes more accurate.
It’s something I’ve never experienced previously until in the last few months and cannot put my finger on what’s happening.
I’ve since purchased a Garmin Glo but haven’t had a chance to test it out. It seems to be confined to my home airfield Elstree and in my specific aircraft, a C172. I’ve tried moving the location of the iPad from lap to yoke with the same result.
Is this something anyone else has experienced and if so am I missing something obvious?
Would appreciate any thoughts
I also use an iPad mini 5 with built-in GPS and I’ve never seen anything like this.
Does it happen everywhere or just at your base?
Have you tried it in another aircraft?
How long before take off do you put the skydemon into navigation mode?
The behaviour seems to only be at my base. The track logs from takeoff at other airfields seems to be “clean”. This is the track log and behaviour on the return journey of the trip
It does appear to only be in my particular aircraft at my base. I’ve only got one example from another aircraft but that log was also clean.
I tend to put it into Navigation mode as soon as doors close therefore it’s a good few minutes prior to getting airborne
Does this really correlate with height over ground, as opposed to time since start-up? Some general-purpose GPS receivers behave a bit erratically for the first several minutes, especially in altitude. In particular, I noticed it consistently occurring with the SiRFstar III chipset.
On the other hand, getting higher in the air would indeed improve the accuracy as low-elevation satellites come into view, being no longer obscured by the structures on the ground. The kinks on your track appear to be within the worst-case positioning tolerance; when I drive on a motorway with a street closely parallel to it, my navigator occasionally recalculates the route as if I were driving on that street, and I know a few places where this happens almost every time. It may be just an unfortunate terrain shape.
It may well be a function of time rather than height. I haven’t done enough analysis / comparison to say either way. I guess the question in my mind is could something have changed / introduced in the way the iPad GPS operates to make this more prevalent? In many years of flying with different iPad models with Skydemon, I’ve never seen erratic performance like this
Are you disabling Wifi & Cellular data and run GPS & SkyDemon before getting into the aircraft? no, then it’s using phone & internet instead of sole GPS sat signals
Do you switch GPS OFF when driving by car or take Jubilee line tube when tranporting it to EGTR? yes, then it’s first run errors
Good points Ibra. I’ve not disabled wifi and cellular so that is the next thing to try.
In the car driving up to Elstree it’s just sitting in the flight back but often in Airplane mode to save battery until I get to the airfield.
This was from a couple of weeks back. Perhaps I should try pressing “Go Flying” sooner also
