Time Lapse Tips

I have a bit of an epic commute at the moment and want to record a time lapse of my trip home after nightshift tomorrow morning.

I have mucked about before but had mixed results. What I need to know is what frame interval to use.

My journey is approx an hour and I want a clip approx 4 mins long on playback at 24fps. My maths aren't great but online calculators suggest 15sec gaps. My quick mental calcs reckon that is too large a gap.

Using a phone (galaxy s3) and my other problem is mounting it to the dash. No tape sticks to any surface. Any help appreciated.
 
How do you set your phone up to take a photo every xSeconds?


My maths would be:

Seconds in trip: ~3600 (60mins * 60secs per minute = 3600)

Photos required to make 4min clip: 5760 (4mins = 240sec, 240sec x 24fps = 5760photos)

Photo Interval: ~0.62sec (3600sec / 5780photos = intervals of ~0.62sec)