I'm examining an iPhone at the moment and it has several images where it is vital to verify the date/time they were taken. The EXIF data has the same date and time as the file created date and time which is to be expected, but the GPS geotagging timestamp is a few seconds adrift.
Does anyone know whether iPhones take the GPS Timestamp from their own internal clock, or from the GPS signal?
Hi Joe,
I might be wrong here, but I am assuming that both dates and times originate from the handsets set date and time. I believe the image file itself is created, and then a few seconds later, the GPS data is written to the EXIF data in the file.
It may take a few seconds for the handset to obtain a GPS fix to write to the file, so that is where you might find the difference lies.
Anyone else have any thoughts on this?
Defiantly the internal clock for Exif
Just in case anyone else runs into the same problem we've run some tests and the results are noteworthy.
EXIF timestamp is, as would be expected, taken straight from the phone, but the GPS timestamp appears to be taken from the iPhone's list of GPS coordinates and is the nearest timestamp it can find in the list to the current phone time.
For example, I am in Manchester at 0500 hours with GPS turned on. I then travel to London, arriving at 1200 hours and take a photo. I turn my handset clock back to 0500 hours and take another photo (still in London).
The EXIF timestamp for the first one would be 1200 hours as would the GPS timestamp, and the GPS coords would point to London. The second photo's timestamps would both show 0500 hours but the GPS coords would be Manchester.
I have still to determine whether the timestamp on the iPhone's internal GPS coords tracking list is taken from the phone or from the GPS signal. I would assume from GPS since it's getting sent that data anyway and it's super accurate, but assuming has never been good in this business.