Do record timestamps have to be unique?

gj3000 over 4 years ago

I am wanting to write data to a FIT file.

Is it valid to write multiple records with the same timestamp, e.g.:

T+0, HR

T+0, speed

T+1, HR

T+1, speed

Or must it be strictly one record per unique timestamp value:

T+0, HR, speed

T+1, HR, speed

Many thanks for any advice. I can't find anything in the spec about this .

0 Ben FIT over 4 years ago

Is it valid or is it expected is the question. The Forerunner 310XT would create files with two records per timestamp. One for data coming from sensors and a second for data coming from GPS. But that was in 2009 and that method was very short lived.

Since that method has not been seen since, many platforms will make the assumption that there is only one record per timestamp, so I would go with the least common denominator. A file with multiple records per timestamp will not convert to CSV very well either, which is another downside.

Also, multiple records per timestamp will bloat the file for multiple reasons. The timestamp is repeated unnecessarily, and the message definitions may end up getting repeated too.

For those reasons, I would stick to one record per timestamp.

0 gj3000 over 4 years ago in reply to Ben FIT

Thank you, makes good sense!!