GPSMAP 65s - GPS speed vs. Speed Sensor 2

[ewald.gruen]

Today I raced through the forest with the 65s on the handlebars at up to 33 km/h and later compared the GPS speed (calculated from the GPX file using a moving average and a 6-second window) with the speed measured by a Speed Sensor 2, and this is the result:

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               | Min Speed | Avg Speed | Max Speed |
GPS Speed      |      1.37 |     16.16 |     33.06 |
Speed Sensor 2 |      0.96 |     16.76 |     33.85 |

According to the header of the GPX file the maximum speed was 9.459 m/s (which equals 34.05 km/h):

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<gpxtrkx:MaxSpeed>9.459</gpxtrkx:MaxSpeed>

A detailed error analysis can be found in the appendix.

speed_comparison.png

[RickN55]

So basically the Speed Sensor is a waste of money if you have a 65s? I looked at buying the sensor for my bike but didn't bother as the speed on the 65s seems to do the job.

[GPSrChive]

So basically the Speed Sensor is a waste of money if you have a 65s? I looked at buying the sensor for my bike but didn't bother as the speed on the 65s seems to do the job.

Waste? No.

Unnecessary for most people, probably yes.

[RickN55]

Well I tried a Speed Sensor 2 today. Nothing but issues. It connected to my 65s but it would work fine showing the speed then the next minute it would drop connection and the speed would show zero and the device would be "searching" for the speed sensor. Then it would work then it would do the same again. No idea what was up with it. I even put a new battery in to see if the battery was low on power but made no difference. So sent it back to Amazon..

[0x01]

Compared against an ordinary cycle computer manually calibrated by ruler, the GPSMAP 65s is extemely accurate (distance matching). I would not spend any money if you have a cycle computer already.