Home › Forums › English › General Discussions regarding BT747

gpx <speed> tag seem to have incorrect value from BT747

pixonian's picture
Sun, 01/10/2010 - 02:48 — pixonian

I'm comparing gpx files generated by BT747 1.68.30 and latest Holux Logger Utility and I see significant difference in numbers.  Both cases use the same log from Holux M-241,  one downloaded using the Holux Utility and converted using the same utility; and for the other -- log was downloaded using BT747 and converted using BT747.  The BT747 does not have "imperial unit" check set, so both programs should be logging in metric.

For a specific test, the actual speed was slightly less than 1000 km/h.  The Holux Utility logs the speed as <speed>965.03</speed> while the same point  from BT747 gets value <speed>268.0650</speed>.  The other points in the log seem to have the similar discrepancy.

I cannot see why these values are different, and so far I tend to think that BT747 somehow incorrectly converts the speed value.

‹ BT747 SW Release Information Thread gpx <speed> tag seem to have incorrect value from BT747 ›
Sun, 01/10/2010 - 02:57 — mdeweerd
mdeweerd's picture

Hi It could be that Holux

Hi

It could be that Holux changed the log format to correspond to the same format as the GPSport 245.  Please set the device log type to Holux GR-245 and see if that solves you problem - it probably does.

The M241 used a 'floating point' format for speed expressed in m/s and in the latest devices this was changed to an integer value expressed in m/s.

I do not (currently) know of a way to detect this easily in the log.

Sun, 01/10/2010 - 03:30 — pixonian
pixonian's picture

Thanks for a quick

Thanks for a quick reply! 


Unfortunately, changing the device type to Holux GR-245 (from M-241) did not solve the problem.  I now get incorrect value for the speed of slightly less than 1000 km/h: <speed>7595552.0000</speed>.

Sun, 01/10/2010 - 03:46 — mdeweerd
mdeweerd's picture

Hi In that case, send me your

Hi

In that case, send me your log and expected values for some points (or the entire converted gpx/CSV log by the Holux utility).

A look at my code did not reveal any apparent issue, so I'll debug it using your concrete example.

Kind regards

Mario

Sun, 01/10/2010 - 05:43 — pixonian
pixonian's picture

Not sure how to attach a file

Not sure how to attach a file here, but below are two complete files.  First is from BT747, second is from the Holux Utility.  Note the difference in speed and elevation values.

[edit:gpx data removed]

Sun, 01/10/2010 - 12:24 — mdeweerd
mdeweerd's picture

Hi You can send to to the

Hi

You can send to to the email address that you find in the 'About' information of the application.

You should also see a 'WebFM Attachments' just above the 'Save' button that allows you to attach files.

I need the binary file to debug this easily.

Tue, 01/12/2010 - 05:12 — pixonian
pixonian's picture

Sounds great, Mario.  I just

Sounds great, Mario.  I just sent you sample files. 

Mon, 01/18/2010 - 00:08 — mdeweerd
mdeweerd's picture

Hi This question was finally

Hi

This question was finally treated in private.

The end conclusion is that the Holux utility is wrong.

Speeds in the gpx file are expressed in m/s, which is what BT747 does.  However, the Holux utility violates that rule by recording the speed in km/h in the GPX file.

'pixonian' confirmed that finding.

Kind regards

 

Mario