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Old October 13th 16, 01:14 AM posted to sci.geo.satellite-nav
Alan Browne
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Posts: 1,339
Default Why are a few timestamps missing?

On 2016-10-12 02:31, Terry Pinnell wrote:
I've been examining the GPS recordings of walks made on my iPhone. The
GPX files should of course contain one text line for each position
recorded, containing position, altitude and a timestamp. But
occasionally (less than 1%) the timestamp is obviously missing. The
4th line of this small extract shows an example:


trkpt lat="50.5573593826"
lon="-4.9283146486"ele22/eletime2016-08-03T09:57:59Z/time/trkpt

trkpt lat="50.5573615199"
lon="-4.9283183366"ele22/eletime2016-08-03T09:58:06Z/time/trkpt

trkpt lat="50.5573525932"
lon="-4.9283242878"ele22/eletime2016-08-03T09:58:07Z/time/trkpt

trkpt lat="50.5573393079" lon="-4.9283319153"ele22/ele/trkpt

trkpt lat="50.5573267350"
lon="-4.9283414707"ele22/eletime2016-08-03T09:58:08Z/time/trkpt

trkpt lat="50.5573160900"
lon="-4.9283459131"ele21/eletime2016-08-03T09:58:10Z/time/trkpt

trkpt lat="50.5573066185"
lon="-4.9283490144"ele22/eletime2016-08-03T09:58:11Z/time/trkpt

trkpt lat="50.5573010445"
lon="-4.9283564743"ele22/eletime2016-08-03T09:58:12Z/time/trkpt

trkpt lat="50.5572247692"
lon="-4.9284306541"ele21/eletime2016-08-03T09:58:20Z/time/trkpt

How does that flaw arise please? I can understand that for various
reasons, recorded trackpoints may be missing completely, or wildly
inaccurate. But how can some be without a timestamp?


You could ask the app provider. Other than that use previous,
interpolate, tolerate or reject.

Terje points out the time difference issue, and that is probably the
best explanation. In non-critical processing that is sufficient unto
the day as long as the positions remain close.

--
She hummed to herself because she was an unrivaled botcher of lyrics.
-Nick (Gone Girl), Gillian Flynn.