batch-shifting time stamps by fractions of a second

[mjshaw]

Ok I'm thinking I'm shooting for the most obscure request ever... though I hope not.

I have a drone company, we do agricultural crop health surveys.  One of our drones has developed a problem in that there appears to be a time drift in the mission timing, it is recording missions as being factionally longer than they actually are. No idea why, the manufacturer is stumped too.  We use the mission data to georeference the .jpg aerial time lapse images to create a mosaic.  Since the mission data is erroneously too long, it means the incorrect GPS position is assigned to the EXIF along with the incorrect pitch, roll, yaw data assigned in the corresponding cache file that is used by the mosaicing software.  I can't edit the mission data, so I need to batch-edit the EXIF time stamps, but by a fraction of a second. I am working with e.g. 596 mission photographs which all need to have their time stamps made later by a constant factor relative to its predecessor. I understand that only whole seconds are recorded in the time stamps but I'm wondering if there is a way of applying the shift in terms of a formula relative to the image sequence number e.g.

exiftool "-AllDates+=0000:00:00 00:00:0.035 X Image Sequence Number"

What are the chances?

All help appreciated.

Mike

[Phil Harvey]

Hi Mike,

ExifTool has a time drift feature built into the -geotag option, allowing you to geotag based on incorrectly timestamped images.   So Exiftool can write accurate GPS coordinates and GPS date/time to the images even though the camera clock was wrong.  If it is a linear drift, you need two known times for ExifTool to do the calculation.  For a non-linear drift you should have more calibrated times and Exiftool will do a piecewise linear interpolation between as many calibration times as you want.  See the Geosync section of the geotagging page for more details.

- Phil