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Time format and absolute time when exporting data
(08-31-2020, 09:46 AM)turboscholz Wrote: To be on the safe side I am just repeating what you said with my own words: By measuring the GPS coordinates you can retrieve the absolute time stamp of the GPS signal, and with that one you can than align the GPS coordinates to the relative time stamp of the experiment.

At least three Satellites are required, so there is not one time stamp… the OS –somehow– decides the time stamp that is given with a location.

(08-31-2020, 09:46 AM)turboscholz Wrote: Idea Wouldn't it be possible to export the measured absolute time stamp of the GPS signal in a separate column in the Location.csv file? This would be totally sufficient for my special use case. I could compare this absolute time with the time stamp and the coordinates of an external GPS device. This means that there is no need to export all experiments with an absolute time stamp.

The absolute time stamp is still not available in experiments at the moment… as we have to change something anyway, we could also do it “right” then…

(08-31-2020, 09:46 AM)turboscholz Wrote: Unfortunately, I see a systematic shift of the gully cover locations found in my data analysis compared to their real locations, which makes me wonder if something is not correct in the overall approach: The found location on the map is most of the time like 3-5 meters behind the real position.

Ok. Thanks for the feedback. We need to check if there is anything we missed in the .phyphox file.

(08-31-2020, 09:46 AM)turboscholz Wrote: Just speculating:
  1. Maybe there is an issue in the beginning of the experiment where it always takes some time to retrieve the first data points from enough GPS satellites to calculate the current location of the smartphone. At the same time, the acceleration sensor is already read out from the start. Can the shift I was talking about can come from this time frame in the beginning of the measurement?
  2. What about time difference (of some seconds) between the absolute time stamp of the GPS signal and the absolute time of the smartphone? Is there a relation which could come into play? I mean, how is the relative time difference between the start of the experiment and the GPS time stamp calculated. I speculate that you somehow must take the absolute time of the smartphone into account, which might be running some seconds off compared to the GPS signal.

1. No; 2. Location is a black box: we get a place, we get a time, nothing else. :/ As navigation apps in fact work, this appears a non-issue to me.

Messages In This Thread
RE: Time format and absolute time when exporting data - by Jens Noriʇzsɔɥ - 08-31-2020, 11:07 AM

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