Training Log Archive: BillD

The Garmin 310XT version: 5.19km, compared to what iPhone recorded at 7.48km. The Garmin track is smoother but does not overlay the roads where I was on them as the iPhone track does. The Garmin track is 100m off on my departure from Start -- the track should follow the south road along the creek and bending n.e. at the eastern end of the pool.

This was a hike around the southern reservoirs of the MDC in West Hartford/Farmington. I started out thinking I would just stick to the Red Loop, but I soon decided to take paths or dirt roads away from the paved Red where opportunity appeared. This was to gain relief from the hoards of prams, bikes, dog walkers and nattering gas bags.

I recorded with both the Garmin and the iPhone (GPS Tracks app).

The iPhone track depicts me as a drunken sailor, slewing back and forth, left and right, staggering along. In truth I was walking a smoother track.

I am not sure what to think about the discrepancies in computed distances. It must have to do with the sampling frequency, which apparently is not affected by the smoothing slide on the AP-rendered maps. The truth probably lies between the Garmin and the iPhone versions, which means that all my tracks for the last few years significantly overstate my distances. I wonder whether the pace figures might also be questionable.

Next steps: examine the software in each instrument to see if the sampling rates can be found and adjusted; dump the GPS data points into a text editor and examine the sampling intervals. Also, compare the lat/lon figures for the area n.w. of the parking lot where the tracks should be 100m apart.

Another thought: does the proximity of the two instruments, one in the left pocket and the other in the right pocket, interfere with signal reception and introduce error?

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C • Garmin 7

iPhone version.

This is the same hike around the MDC reservoir area as shown above in the Garmin version. While this is double counting the workout, I wanted to show the discrepancies between the results from the two instruments.

See comments above in the Garmin version discussion.

Following up on the discrepancies between Garmin and iPhone (GPS Tracks app) for today's hike in the MDC:

I find that the Garmin was set to Smart Recording. I have now set it for 1 second sampling.

I find that iPhone's GPS Tracks app was set to High for sampling rate. I have now set it to Medium.

I expect the two instruments will come closer together in rendering tracks for the next trail hike.

Around Stratton Brook SP in a back and forth route to try out my new (out of production ergo not too expensive) Garmin 310XT. The track is a lot smoother than what the iPhone yields, probably because of a longer sampling interval. However the GPS accuracy seems less, judging from track disparity when retreading one segment. Starting and stopping the timer is definitely easier than with the iPhone ensconced in a protective arm band or pocket. Hit the lap button at arbitrary junctions and found that the watch records and will show through scrolling the time and distance of each lap. However, it appears that the only export method is via the ANT+ device to GarminConnect and that avenue does not seem to transmit any lap data. I wonder if there is other software that can pull the data off the watch, with or without the ANT+, and without involving GarminConnect website.

Really nice to have some cool weather. Temp about 55F, clear sky, empty woods. Doesn't get better than that.

C • lap data 5