Fitbit sense tracks swimming incorrectly

[boshoff.steenek]

I recently got a Sense, and it is useless to track swimming lap.  The table below shows huge variation from the actual swam distance.

Does anyone else experience similar problems?

Date	Distance calculated manually	Distance recorded on SENSE	Difference	Coefficient of variation
05-Nov-20	1 550	1 700	150	10%
06-Nov-20	1 550	1 825	275	18%
09-Nov-20	1 500	1 900	400	27%
12-Nov-20	1 600	1 700	100	6%
13-Nov-20	2 050	2 150	100	5%
14-Nov-20	2 500	2 750	250	10%
16-Nov-20	1 500	1 125	-375	-25%
17-Nov-20	1 600	2 375	775	48%
18-Nov-20	1 700	1 800	100	6%
19-Nov-20	1 600	1 750	150	9%
20-Nov-20	1 600	1 950	350	22%

[Rich_Laue]

How has your lap count been? 

[boshoff.steenek]

Thank you for your response.
The table shows that the lap count is equally inaccurate and inconsistent.

[Rich_Laue]

Your table only shows distance, not Laps. Most are within 100 and within the 10% error. 

[boshoff.steenek]

Apologies, I have not included the laps in the previous table, it is included in the table below.

The big concern is that the variation from the actual is inconsistent.  On one occasion the Device had 48% more laps than actual, an on another it had 25% less than actual

Date	Laps counted manually	Distance calculated manually	Laps counted on sense	Distance recorded on SENSE	Difference	Coefficient of variation
05-Nov-20	62	1 550	68	1 700	150	10%
06-Nov-20	60	1 550	73	1 825	275	18%
09-Nov-20	60	1 500	76	1 900	400	27%
12-Nov-20	64	1 600	68	1 700	100	6%
13-Nov-20	82	2 050	86	2 150	100	5%
14-Nov-20	100	2 500	110	2 750	250	10%
16-Nov-20	60	1 500	45	1 125	-375	-25%
17-Nov-20	64	1 600	95	2 375	775	48%
18-Nov-20	68	1 700	72	1 800	100	6%
19-Nov-20	64	1 600	70	1 750	150	9%
20-Nov-20	64	1 600	78	1 950	350	22%
25-Nov-20	46	1 150	53	1 325	175	15%

[boshoff.steenek]

Updated table:

Date	Laps counted manually	Distance calculated manually	Laps counted on sense	Distance recorded on SENSE	Difference	Coefficient of variation
05-Nov-20	62	1 550	68	1 700	150	10%
06-Nov-20	60	1 550	73	1 825	275	18%
09-Nov-20	60	1 500	76	1 900	400	27%
12-Nov-20	64	1 600	68	1 700	100	6%
13-Nov-20	82	2 050	86	2 150	100	5%
14-Nov-20	100	2 500	110	2 750	250	10%
16-Nov-20	60	1 500	45	1 125	-375	-25%
17-Nov-20	64	1 600	95	2 375	775	48%
18-Nov-20	68	1 700	72	1 800	100	6%
19-Nov-20	64	1 600	70	1 750	150	9%
20-Nov-20	64	1 600	78	1 950	350	22%
25-Nov-20	46	1 150	53	1 325	175	15%
26-Nov-20	64	1 600	70	1 750	150	9%

[boshoff.steenek]

Updated table:

Date	Laps counted manually	Distance calculated manually	Laps counted on sense	Distance recorded on SENSE	Difference	Coefficient of variation
05-Nov-20	62	1 550	68	1 700	150	10%
06-Nov-20	60	1 550	73	1 825	275	18%
09-Nov-20	60	1 500	76	1 900	400	27%
12-Nov-20	64	1 600	68	1 700	100	6%
13-Nov-20	82	2 050	86	2 150	100	5%
14-Nov-20	100	2 500	110	2 750	250	10%
16-Nov-20	60	1 500	45	1 125	-375	-25%
17-Nov-20	64	1 600	95	2 375	775	48%
18-Nov-20	68	1 700	72	1 800	100	6%
19-Nov-20	64	1 600	70	1 750	150	9%
20-Nov-20	64	1 600	78	1 950	350	22%
25-Nov-20	46	1 150	53	1 325	175	15%
26-Nov-20	64	1 600	70	1 750	150	9%
27-Nov-20	64	1 600	74	1 850	250	16%

[boshoff.steenek]

See update below:

Date	Laps counted manually	Distance calculated manually	Laps counted on sense	Distance recorded on SENSE	Difference	Coefficient of variation
30-Oct-20		Not counted		2 300
31-Oct-20		Not counted		1 850
03-Nov-20		Not counted		2 100
05-Nov-20	62	1 550	68	1 700	150	10%
06-Nov-20	60	1 550	73	1 825	275	18%
09-Nov-20	60	1 500	76	1 900	400	27%
12-Nov-20	64	1 600	68	1 700	100	6%
13-Nov-20	82	2 050	86	2 150	100	5%
14-Nov-20	100	2 500	110	2 750	250	10%
16-Nov-20	60	1 500	45	1 125	-375	-25%
17-Nov-20	64	1 600	95	2 375	775	48%
18-Nov-20	68	1 700	72	1 800	100	6%
19-Nov-20	64	1 600	70	1 750	150	9%
20-Nov-20	64	1 600	78	1 950	350	22%
25-Nov-20	46	1 150	53	1 325	175	15%
26-Nov-20	64	1 600	70	1 750	150	9%
27-Nov-20	64	1 600	74	1 850	250	16%
03-Dec-20	80	2 000	82	2 050	50	3%