PB wrote:Finally, the GNSS signals need to be 'filtered' to make the raw data more stable and of practical use.
Indeed. All devices have filters. From previous posts on here - no position system can currently cope with an aircraft doing aerobatics. For VFR bimblers - any GPS signal, accurate to 100m is probably "good enough" what what they are doing. A bit different if you are doing a CAT3b Autoland using a LVP. There is a reason that Sky Demon wont provide a glideslope below 500 feet.
In phones / tablets there is also lots of "magic" going on to combine sources, which is hidden. It is possible to combine multiple sources to make a location more accurate.
Unless something has changed recently, iPhone apps don't get access to any of that - they just get x, y, z coordinates and an accuracy number from the underlying system. Apps have no way of knowing whether the provided location is from a sub-centimetre accurate, differential multi channel external device or because you are near a known wifi hotspot. Android provides a bit more info (including satellite status) , and it is possible to access external devices directly, but that brings support headaches (but if you are Garmin - you can get details from your own branded devices) so its rare for an app to bother.
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