HRM data is out of sync with GPS data

[Skaistis]

For some time my logged HRM data (ANT+) is delayed compared to GPS data. This issue appears in oruxmaps statistics and exported files (samples below).

Could it be because my phone (android v.2.3.4) is disconnected from mobile network (I've removed its SIM card) and it cannot sync time automatically? If this is the case, how could I solve the issue without mobile networks?

 



For example offset in GPX file:

[Start of HRM data]

Code Select Expand

<extensions>
<om:oruxmapsextensions xmlns:om="http://www.oruxmaps.com/oruxmapsextensions/1/0">
<om:ext type="TYPE" subtype="0">0</om:ext>
<om:bpm>
78 2015-04-19T14:38:43Z
78 2015-04-19T14:38:44Z
77 2015-04-19T14:38:45Z
75 2015-04-19T14:38:46Z


[Start of GPS data]

Code Select Expand

<trkseg>
<trkpt lat="54.6797272" lon="25.2513557">
<ele>124.06</ele>
<time>2015-04-19T14:30:47Z</time>
</trkpt>
<trkpt lat="54.6797786" lon="25.2513500">
<ele>123.88</ele>
<time>2015-04-19T14:31:14Z</time>
</trkpt>
<trkpt lat="54.6798438" lon="25.2513266">
<ele>123.51</ele>
<time>2015-04-19T14:31:18Z</time>
</trkpt>
<trkpt lat="54.6798949" lon="25.2513027">
<ele>123.06</ele>
<time>2015-04-19T14:31:20Z</time>
</trkpt>

[Skaistis]

Update

As I expected this issue occurs because of different time sources for HRM and GPS logs.

HRM time in track log is taken from phones clock.

GPS time in track log is taken from satellite(?).



So in result you will always have some time offset because satellite clock and phone clock will differ.



Is this a bug or expected behavior?

[orux]

Update

As I expected this issue occurs because of different time sources for HRM and GPS logs.

HRM time in track log is taken from phones clock.

GPS time in track log is taken from satellite(?).



So in result you will always have some time offset because satellite clock and phone clock will differ.



Is this a bug or expected behavior?

Hello;



The GPS position fix includes a timestamp. Because there may be a delay between the time when the GPS signal is received, and the OS sends the data to the application and the data is processed, it is normal to use the timestamp provided by the GPS, because it is the true time.



Many HRM data packets do not include a timestamp. Therefore it is necessary to use the phone time itself.



Today it is normal to have the phone time synchronized, so this should not be a problem.



orux