Some individual Garmin watch units have a sensor defect that prevents live jump measurement. Surfr detects this automatically and switches the watch to Surfr.AI mode, so you still get accurate jump heights, but just after syncing instead of live on the watch. If your watch pointed you here, this article explains what is going on and how to report the issue to Garmin.
What's happening
Surfr uses two sensors in your watch: the accelerometer and the gyroscope. Both are asked for 100 measurements per second (100Hz). On an affected unit, one of the two silently delivers fewer, for example 98.3 instead of 100 per second. The difference is constant for a given watch, month after month, so it behaves like a defect in that individual unit, not a software bug.
Live jump detection needs the two sensor streams to stay in sync. When they drift apart, jump heights on the watch would be wrong, so Surfr turns them off and uses Surfr.AI instead.
ℹ️ Surfr checks for this with a sensor test on the watch: it measures the accelerometer alone for 90 seconds, then the gyroscope alone for 90 seconds. If the two rates differ by 0.4% or more, or either sensor runs below 99.6Hz, the unit is affected. You can redo the test anytime via Settings → Check Compatibility on the watch.
What Surfr does about it
In Surfr.AI mode your sessions work as usual:
The watch records GPS, speed and raw sensor data
Surfr.AI computes your jump heights automatically right after the session is imported into the Surfr app. Nothing extra to do for you.
Big Air mode stays available; you see the heights afterwards in the app
Session files are bigger, so syncing takes a bit longer
Why this is a Garmin issue
This is a defect in the individual watch unit's sensor hardware. It is not caused by Surfr and unfortunately not something we can fix on our side, only Garmin can, with a firmware update or by repairing or replacing the unit. Surfr detects the issue and works around it, but the root cause is in the watch.
That is why we recommend reporting it to Garmin. The more users report it, the higher the priority on Garmin's side.
How to report it to Garmin
Go to support.garmin.com and search for your watch model.
On your watch's support page, choose Contact Us / Support Center. Depending on your country you'll be offered email (a support case form), chat, or phone. Garmin has no public support email address, so the form is the email route, and replies arrive in your inbox.
Look up your details first as Garmin will ask for them: software version and serial number are on the watch under Settings → System → About, or in Garmin Connect under your device.
Copy the message below and fill in the placeholders.
Attach the example file (download button below). If you took a photo of the Surfr sensor-test result screen, attach that too please, as it shows your own unit's measured rates.
Optional but stronger: also attach one of your own sessions. In connect.garmin.com, open a Surfr activity, press the gear icon and choose Export Original (a ZIP containing your FIT file).
Copy this message to Garmin
Subject: [Watch model] - accelerometer/gyroscope sample-rate mismatch on my unit
Hello Garmin Support,
My watch (model: [model], software version: [version], serial number: [serial]) appears to have a per-unit sensor defect: when a Connect IQ app records the accelerometer and the gyroscope at 100 Hz through the standard SensorData API, the two sensors deliver different effective sample rates.
This was detected by the Surfr app (a kitesurfing Connect IQ app) using an on-watch diagnostic that measures each sensor separately for 90 seconds against the system timer. On affected units the mismatch is constant in size and direction over months, so it looks like a hardware/clock issue in the unit itself, not an app problem.
Because the sample rates differ, the time offset between the two sensor streams is not stable at runtime: it keeps growing while recording. The alignment between gyroscope and accelerometer at one moment is no longer valid a few minutes later, so the issue cannot be worked around with a per-session calibration that measures the offset once and any measured offset is outdated within minutes.
A software correction is not possible either: this model does not support the newer Connect IQ SDK sensor capabilities, so accelerometer and gyroscope data arrive without sample timestamps. Without timestamps, an app has no way to re-align the two streams on the watch.
Attached is an example FIT activity recorded on an affected fenix 6S (firmware 28.02) where the mismatch is clearly visible: over the same 44-minute recording the file contains 264,100 gyroscope samples but only 259,800 accelerometer samples. Both requested at 100 Hz. This can be verified with the FIT SDK by counting accelerometer_data vs gyroscope_data messages.
Because the two sensor streams drift apart, features that need synchronized motion data (in my case, live jump-height detection while kitesurfing) cannot work on this unit.
Could you please advise whether this can be resolved with a firmware update, or whether my unit qualifies for repair or replacement?
Thank you,
[Name]
Download the example file
This is a real session recorded on an affected fenix 6S. Both sensors were asked for 100Hz; over the same 44-minute recording the gyroscope delivered 264,100 samples but the accelerometer only 259,800, so 4,300 samples missing, a 1.6% divergence. Anyone (including Garmin support) can verify this with Garmin's own FIT SDK by counting accelerometer_data vs gyroscope_data messages.
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