logging settings are not followed when GPS signal is lost or off

[987]

Checking if anyone else can confirm this.

GPSmap 66st with software 4.10, GPS 2.70.
For activity recording o have the following settings:
Output format FIT and GPX.
GPX auto archive: when full.
Trip recording: always
Record method: time, interval 15 seconds.
auto pause: off, auto start: true.
activity type: other.

I have set the track recording options to log one point every 15 seconds (or longer apart to conserve battery).
But occasionally, when satellites are lost (in building or tunnel), the logging occurs every second.
When the satellites are found again, the tracking goes back to 15 seconds.
This can bee seen under the recording control and i page.

Also when selecting GPS off (from satellite page), that logging stops entirely
(not even time and barometer is logged), even though the log control shows a
green arrow that recording is ongoing.
When GPS is enabled (from the satellite page), the logging starts at a rate
at 1 point per second during the time when the GPS position is not fixed.
When GPS satellites are found, then it goes back to logging according to
setting, once per 15 seconds in my case.

I consider these cases a bug. Logging should work according to settings, with GPS signal
or without, and even if GPS is off. Of course, one can only log what is
present. but at least it should work.


Have anyone else noticed this behaviour?

[GPSrChive]

Interesting observations. We will have to do some testing....

[987]

i observed that this does not occur when waking up from expedition mode and while satellites are still being searched.
So at least here it seems to work better, if nothing is touched until GPS signal is found.
If i for some reason stop and resume logging from Recording control while GPS signal is not found, it will start to log per one second.

So all in all:
It is mainly during normal operation, when GPS signal is lost or not yet found that it log every second (instead of what is given in setup).
or not logging at all, if one disables GPS satellites from the menu.

[GPSrChive]

It may be (I am guessing here) that the engineers decided that when logging is active but a satellite signal is not, they want to add a new 'good track point' to the log as soon as possible, and logging at the default trip computer rate (1Hz) ensures that a valid track point will be added ASAP once the satellite connection has been restored, at which time the unit returns to normal user configured logging rate.

If, for example, the user had a long delay between logging track points (long time or distance), it would potentially be possible that the satellite signal is restored just after a track point would have been saved, resulting in a longer than necessary delay before the next valid track point is added to the track log.

[987]

Hi.
I argue opposite, but i get your point.
The effect of having too frequent logging is a bit of battery usage (i don't know how much), plus a lot more points saved.
An option would be to log according to time, and log one point immediately on GPS signal and then start to count the clock again. It would give one more point, but not many.

Example.
I am out for about 15 hours.
At a logging rate of 15 seconds, i expect a total of around 3600 points.
When i checked the status i had some 15 000 points logged. Approximating that around 3 hours (10 800 points) came from times when there was no GPS signal.
Assume now that the time without GPS signal would have been 5-6 hours, then the log would have got full.
For somebody that has not set up auto archive of logs, it may be an issue that the log is full after 20 000 points.

[GPSrChive]

I would like to see those tracklogs.

What coordinates did the GPSr use for the trackpoints where no GPS signal was available?

[987]

Hi.
After i finished, i went to recording control and saved the activity (first save).
After that i went to Saved activities and saved to track (second save).

Now i have 3 files on the GPS:
1. ./Garmin/Activities/2020-05-01 16-33-39.fit (This is from my first save).
2. ./Garmin/GPX/Archive/2020-05-01 163339.gpx (This is from my first save).
3. ./Garmin/GPX/Track_2020-05-01 16-33-39.gpx (This is from my second save).


1.
The fit file, when converting it to GPX (using gpsbabel) just to check how many points it has, it shows 3478 points, timings look to be 15 seconds apart.
On the GPS however, under the Saved activities, this activity shows 17571 points, but when exporting it i could only see 3478 points.
(note that i do not have a proper program to load the FIT file).

2.
This GPX track, which also came from the first save, contains 3478 points, and timings are 15 seconds apart.

3.
The GPX Track file which was saved when saving the activity to track, shows it has 17571 points. I can clearly see that timings are 1 second apart sometimes (when the GPS signal was lost).
The Position (always) shows the last known position. When signal is present, the current position is saved. When GPS signal is lost, it keeps the last know position every second, until the signal is found again, and then the new position is shown in the last point with 1 second interval, and then it moves back to 15 second interval logging.

[GPSrChive]

Can you please email those files to webmaster@gpsrchive.com?

[987]

Preferably not, since they give away positions.
It is very easy to reproduce the situation.
Set the settings as i have them (see fist post), run in normal operation, go to the satellite page, disable the GPS, go indoors where reception is poorer, go again to the satellite page and enable the GPS. Check that the recording is running. While GPS signal is not fixed, the logging occurs once per second (one can see this under the recording option and info page).
The same log frequency will be visible in the logs too (as describe two messages back).

[987]

The one second logging which occurs when the GPS signal is lost, also happens if i have logging settings like this:
Output format FIT and GPX.
GPX auto archive: when full.
Trip recording: always
Record method: Auto, most often. (this is the change compared to first post).
auto pause: off, auto start: true.
activity type: other.

it seems the one second logging always happens when GPS signal is lost. feels like a bug to me, because the auto setting normally reduces logging points when no motion is detected.