Anthropological fieldwork with a Garmin Edge 305 with Heart Rate monitor

Garmin produces several devices that combine a heart rate monitor with a GPS. This combination has great potential for logging information about location and exertion as long as one is outdoors with GPS reception with +/- 10m of error per measurement. The 305 series of the Forerunner and the Edge GPS units use the SiRF Star III GPS chip. Out of the box the firmware was many versions old and to be updated to v3.2.

The Garmin Forerunner is wrist mounted and is primarily for runners and mountain climbers, and the Garmin Edge is designed for use on bicycles. Both have an optional wireless heart rate monitor, and the Edge also has an optional cadence measuring system that attaches both to one wheel an to the crank arm of the pedal.

The Forerunner seems like the obvious choice for studies of walking subjects, but unfortunately only the Edge combines a barometer with the GPS to produce barometer stabilized altitude readings. I'm told that in tests with both units the altitude measurments from the Garmin Edge contained much less noise than the Forerunner in Z values (Minetti, pers comm, 14 Nov 2006).

The problem remains that the Edge does not have a wrist strap or an obvious way to carry it without mounting on a bike handlebar. One idea is to put the Edge into a small iPod case with a clear window as the Edge is only slightly larger than the iPod Nano.

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Software Compatibility

My goal is to import these data into a GIS package for further analysis, but the software that comes with the Garmin units doesn't make it easy. I would like to have GPS positions with heart rate BPM for each location.

The Garmin Edge comes with a CD containing Garmin Training Center software. This software allows you to download TCX files containing History, Workouts, and Courses. Data is logged in the History file when the timer is started and these files contain the accumulated information from recent outings. The Training Center software lets you see summary information on outings but you cannot view the raw data in table form.

Garmin TCX files can be saved out of Training Center 4 but no other more widely readable format is supported. The TCX files are actually XML files and if you change the suffix to XML the raw data can be opened as "read only table" in MS Excel.
The software iSmartTrain, currently in beta (v20) with no time restrictions, lets you import a TCX file and view the raw history data in a clean table format. These records are cleaned up a bit and can the be cut and pasted into Excel and imported into Arcmap using the Import XY command.

Connection to GIS

Several programs allow you to convert data between a Garmin GPS and a vector GIS format like Shapefile. Two programs designed with Shapefile compatibility are the free DNR Garmin and GPS Utility. The latter displays the heart rate data and other History file data, but it is limited to 100 records in Free mode.

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Data Quality

The on screen display indicated that the error was between 6 and 10m most of the time in recent tests in Berkeley, CA (WAAS enabled). This spatial accuracy is relatively poor and I hope to use a differential GPS (Trimble) when possible.

The device can log data at 1 sec intervals for about 3.5 hrs at which point the 8mb memory fills up.

Alternately in "Smart Recording" data is only recorded when change in direction, speed, or heart rate is detected by the device. Obviously this choice compromises the consistent log of the heart rate monitor, although one can extrapolate that the heart rate is constant until the next reading. Too bad a setting for 5 sec intervals at 16 hours isn't available.

This table shows data where I stop to stretch my legs after running uphill where my heartrate reached 165 BPM in SmartRecording mode. The Dist_M field barely while I was stationary, but it continued to log points because the heart rate monitor detected some change. These data suggest that a 5 BPM change in heart rate causes the device to log a point.

Time 0:06:08	Heart 160	Speed_MPM 13:09	Dist_m 0.481	Alt_M 289	Lat 37.88325	Long -122.25439
0:06:12	160	11:53	0.487	289	37.88317	-122.25438
0:06:17	158	20:48	0.491	291	37.88311	-122.25436
0:06:23	155	0	0.494	289	37.88308	-122.25437
0:06:24	153	0	0.494	289	37.88308	-122.25437
0:06:28	144	0	0.494	290	37.88309	-122.25437
0:06:29	145	0	0.494	289	37.88308	-122.25436
0:06:31	138	0	0.494	289	37.88308	-122.25436
0:06:39	133	0	0.495	289	37.88309	-122.25436
0:06:44	128	0	0.496	289	37.88310	-122.25435
0:06:51	123	0	0.496	289	37.88310	-122.25434
0:06:57	118	0	0.496	289	37.88310	-122.25434
0:07:01	113	0	0.496	289	37.88310	-122.25434
0:07:09	108	0	0.497	289	37.88310	-122.25434
0:07:13	103	0	0.497	290	37.88310	-122.25434
0:07:16	96	0	0.497	290	37.88310	-122.25433
0:07:17	96	0	0.497	290	37.88310	-122.25433
0:07:29	92	0	0.497	291	37.88310	-122.25434
0:07:36	87	0	0.497	291	37.88310	-122.25435
0:07:43	82	0	0.498	291	37.88309	-122.25435
0:07:48	77	0	0.498	291	37.88309	-122.25435
0:08:06	72	0	0.498	291	37.88309	-122.25436
0:08:45	67	0	0.499	290	37.88308	-122.25435
0:09:12	70	0	0.501	290	37.88306	-122.25434
0:09:16	77	0	0.503	291	37.88303	-122.25430
0:09:20	86	14:48	0.508	292	37.88298	-122.25426
0:09:22	97	14:33	0.51	291	37.88295	-122.25423
0:09:24	100	11:17	0.513	290	37.88291	-122.25421

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