Update: Garmin has released software version 3.70, which enables 1-second logging. About time!
I’m now pretty sure that the smooth curves I see on my activities on Garmin Connect are due to problem with the «smart recording» of the Garmin Forerunner 310XT – probably a bug in the latest firmware. Yesterday I did 18km of xc skiing with a friend, and below is a comparison of the logs from two 310XTs using different firmware. The difference is clear: The graphs from the 3.20.00 firmware lack details compared to the 2.90.00 graphs. A look at the raw data also shows that the 3.20.00 firmware logs heart rate far less frequently than the 2.90.00 firmware.
Garmin’s manual for the Forerunner 310XT says:
The Forerunner uses smart recording. It records key points where you change direction, speed, or heart rate.
Sounds good, but how «smart» is it really? Below are some details from two Forerunner 310XT, on two skiers at the same time.
Forerunner 310XT with 2.90.00 firmware
Detailed graphs for speed, elevation and heart rate, as one would expect:
Full log on Garmin Connect: http://connect.garmin.com/activity/69496587
Forerunner 310XT with 3.20.00 firmware
Using the latest firmware, there is very little detail compared to the graphs above: The elevation graph is far too «smooth», and the heart rate graph contains so little details, and so much interpolation, that it can not be used to monitor the hear rate properly:
Full log on Garmin Connect: http://connect.garmin.com/activity/69493483
Comparing the raw data
I used GPS Visualizer to produce plain text tables of Garmin’s TCX files exported from Garmin Connect. This shows what is going on: The newest firmware does not log heart rate frequently enough.
Raw data from the 2.90.00 firmware:
Raw data from the 3.20.00 firmware:
As you can see, the 3.20.00 firmware logs GPS coordinates and elevation frequently, but has very large gaps – up to 40 seconds – between each time the heart rate is logged. The 2.90.00 firmware logs heart rate much more frequently.
Garmin working on fixing the problem?
As mentioned in a previous blog post, Garmin is aware of this and working on a fix. Still, shouldn’t they acknowledge this as a known issue, and inform their customers? This is all I have heard from Garmin, after contacting them twice on Twitter:
I have also contacted Garmin Support, who did not understand the problem, and simply advised me to do a «hard reset» of the 310XT – useless, really (if anyone from Garmin reads this, the Kana reference is KMM20072186I15977L0KM).
If you own a Garmin Forerunner 310XT, I recommend not updating to the latest firmware (history here), but instead contact Garmin Customer Support asking them to fix this problem.
[This post is written in English, since I hope it may be interesting for non-Norwegians. I have also posted a message on the Garmin Forum]