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GPX Missing Speed, Course and Accuracy Information #341

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
What steps will reproduce the problem?

1. Export to GPX
2. SPEED and COURSE and accuracy (# <fix> Type of GPS fix
# <sat> Number of satellites
# <hdop> HDOP
# <vdop> VDOP
# <pdop> PDOP)
 attributes are empty

3. These values are present in the CSV export (SPEED, BEARING AND ACCURACY)

What version of MyTracks are you using? - 1.0.17

On what version of Android? - CyanogenMod6.0 (Froyo)

On what phone? G1/Dream

See attached files.

Original issue reported on code.google.com by brent.m....@gmail.com on 17 Feb 2011 at 1:55

Attachments:

GoogleCodeExporter commented 9 years ago 
There are no speed and bearing tags in the base GPX specification.  Even if 
there were, speed should not be included as it is derived from the location and 
time and not measured directly.  I think including it would imply that some 
other sensor were used to obtain a more accurate speed.

The fix, sat, and *dop tags are only allowed in waypoint elements.  We should 
include them in the waypoints if available, but note that the attached .gpx 
file will not change because there are no waypoints in there.

Maybe there is a standard extension schema for GPX to include that information 
in the track points?

Original comment by jaredcas...@gmail.com on 17 Feb 2011 at 5:13

GoogleCodeExporter commented 9 years ago 
Cheers for the response.

All of the mentioned tags/attributes are part of the GPX 1.0 schema (the 
version used by MyTracks)

http://www.topografix.com/gpx_manual.asp

The optional tags can be part of either waypoints or trackpoints.

Here are examples of the utility of having speed and course info (which are 
both in fact derived from time and location as you mentioned):

1) Thematic maps based on the speed attribute
2) Geo-tagging photos and being able to create symbology indicating the 
direction of the photo.

Original comment by brent.m....@gmail.com on 17 Feb 2011 at 6:32

GoogleCodeExporter commented 9 years ago 
Ah didn't realize those were part of the 1.0 schema.  The development head of 
MyTracks moved to GPX 1.1 recently, and TopoGrafix removed those tags from the 
track points in the 1.1 schema. See here for a big discussion about it: 
http://tech.groups.yahoo.com/group/gpsxml/message/746.

So MyTracks can either revert the recent change and go back to the 1.0 schema 
and include these, or use some defined extension for the 1.1 schema.

I'm still personally in the camp that speed and course info should not be 
included unless they are read from a sensor (but I'm not a MyTracks dev of 
course).  If the application using the gpx file wants that info it can easily 
recalculate it, and MyTracks should not make assumptions about how the 
application wants speed derived from the location and time.  The precision info 
could be included though.

Original comment by jaredcas...@gmail.com on 17 Feb 2011 at 7:08

GoogleCodeExporter commented 9 years ago 
This is almost the same as 243.  Marking it a dupe of that VeryLow priority bug.

Original comment by sandordo...@google.com on 18 Feb 2011 at 5:15

GoogleCodeExporter commented 9 years ago 
This is a bit old issue, but I still want to comment towards additional speed. 
Speed reported by GPS could be doppler speed which is much more accurate 
compared to "delta location divided by delta time". So it would be nice to have 
Doppler-based -speed reported. 

But how to achieve this if Android GPS API does not return speed is a different 
thing. Probably you can get it via Android NMEA-sentences.

Original comment by jori.ham...@gmail.com on 11 Oct 2012 at 5:40

GoogleCodeExporter commented 9 years ago 
This issue is closed, as well as the one it is marked as a duplicate of.
However, two separate parts of this enhancement:

* In addition to doppler speed, the ANT+ sensors (and hopefully BTLE soon) 
could report speed. This should be included in .tcx export too, as well as the 
reported distance.
* vdop etc is something I miss for postprocessing GPS information, to get 
better distance calculations. For instance Garmin makes a better job than 
analyzing GPS points.

Original comment by gerhard....@gmail.com on 1 Sep 2013 at 9:32