I have a Sigma STS 16 computer with speed & cadence sensors. I've found that this calculates "ride time" somewhat differently to my GPS-enabled Cyclemeter iPhone app.

Cyclementer shows a breakdown of ride time and stopped time, presumably based on on GPS data showing whether you're moving or not, e.g. at traffic lights. I expected the Sigma to simply show the time time that the bike wheels were moving, i.e. recording wheel revolutions. But the figures don't match.

For example, this morning Cyclemeter showed 38m:16s ride time with 7m:08s stop time, but the Sigma showed 41.00m ride time. It's not showing the total time on the bike, which would be 45m:24s, or the actual time the GPS showed I was moving.

I know it's possible for the GPS to be slightly inaccurate or to have some "lag" depending on how often the position is sampled, but this shouldn't amount to a nearly 3 minute difference.

Any ideas what is going on?

Thanks!

John