The mysteries of Garmin's gmn files


Legendary Member
I've got my own Garmin download scripts on my (unix) laptop, cobbled together from the bits and bobs with, at its heart, the 'garmin_tools' package. In short, the scripts pull the Garmin gmn files off of my Edge 305 and creates tcx files from them. I can then upload those tcx files to wherever.

After giving solid performance for many years, there's been a hiccup and they (the scripts) stopped generating track data on the output .tcx files. Everything else is there and correctly formatted; date and time, ride totals and averages, etc - it's just the location specific data that is missing. I suspected a change in the gmn format; perhaps a change in a field length or somesuch. I feared I was going to have to get my hands dirty and delve into the heart of it all, start looking at the code and raw data to see what was happening.... I was not looking forward to it, my coding days are long gone.

Image my surprise (and relief!) when this morning's download generated a full and well formated tcx file. So, I deleted the incomplete tcx files and attempted to regenerate them... but I got the same results; incomplete data. I've no idea what's gone on or why half a dozen or so gmn files have given rise to this, but it seems (touch wood) to be okay now. Who knows what Garmin do or how those gmn files are formatted.

(Btw, I'm able to get the tcx files via other means, I just use my old scripts out of a sense of loyalty. Like my Edge 305, they will one day reach the end of their useful life)
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