Found an error(?) in intensity_factor definition in Profile

Hello!

In the definition of the intensity_factor field in the session message the Profile documentation says this is an uint16 and that you have to apply a scale of 1000. That is, divide the raw uin16 value by 1.000.

If I do so, all my resulting values are exactly a factor 3.6 too high. Which means that the scaling factor must be 3600, not 1000?!

My software processes other scaling of uint16 values correct (like avg_speed, max_speed), so the error is not likely to be in my routines.

Kind regards,

Frank

0 Ben FIT over 5 years ago

1000 is the correct scale for the intesity_factor field in the session message.

Intensity Factor (IF) is defined as the ratio of Normalized Power (NP) and Functional Threshold Power (FTP).

IF = NP / FTP

If the IF value does not look correct the issue is probably that the FTP setting on the device is wrong. I would check the FTP setting on the device to make sure it is correct. You can also look at the NP value in the file and divide it by the current FTP setting on the device. That should confirm the issue. Looking the activity summary on the device should show the NP value and scaled IF value. If the FTP setting is wrong, too low in this case, then the IF value shown on the device will be too high. NP is not dependent on FTP, so it is probably correct.