GPS#
GPS (Global Positioning System) provides position, speed, and elevation data to both the Garmin Edge MTB and the Apple Watch Ultra 1 during rides. Both devices record independent GPS tracks, but at different precision levels.
In the Network#
| Device | GPS Support | Accuracy |
|---|---|---|
| Garmin Edge MTB | Multi-band GNSS (GPS + GLONASS + Galileo) at 5 Hz | High — multi-constellation |
| Apple Watch Ultra 1 | Dual-frequency L1+L5 GPS + GLONASS + Galileo + BeiDou + QZSS | Highest — dual-frequency |
Signals Used#
L1 (1575.42 MHz)#
The primary civil GPS signal broadcast by all GPS satellites. Both devices receive L1. All GPS-capable consumer devices support L1 — it carries the C/A (Coarse/Acquisition) code used for standard positioning.
L5 (1176.45 MHz)#
A newer, higher-power civil signal. The Apple Watch Ultra 1 receives L5 in addition to L1, enabling dual-frequency positioning.
Dual-frequency GPS corrects for ionospheric delay — the primary source of GPS positioning error. When the receiver tracks both L1 and L5 simultaneously, it can calculate the differential delay and remove it, significantly improving accuracy in environments where signal paths are long or distorted:
- Dense forest (tree canopy deflects and delays signals)
- Urban canyons (buildings cause multipath reflections)
- Valley riding (restricted sky view, oblique signal angles)
GNSS Constellations#
Both devices use multiple satellite constellations beyond GPS:
| Constellation | Origin | Bands |
|---|---|---|
| GPS | USA | L1, L5 |
| [REDACTED] | Russia | L1 |
| Galileo | EU | E1, E5a |
| BeiDou | China | B1 (Watch only) |
| QZSS | Japan | L1, L5 (Watch only) |
Using multiple constellations increases the number of visible satellites at any given location, improving fix speed, accuracy, and availability under tree cover or in valleys.
Recording Rate#
The Garmin Edge MTB records GPS position at 5 Hz — five position samples per second. This produces smooth, detailed tracks on fast descents and tight switchbacks. Standard consumer GPS typically records at 1 Hz (once per second), which smooths out corners and loses detail at speed.
The Apple Watch Ultra 1 records an independent GPS track via the Workout app. Its recording rate is app-dependent; the Workout app defaults to 1 Hz but third-party apps can request higher rates.
Elevation#
Both devices include barometric altimeters for elevation data. GPS elevation accuracy is significantly worse than horizontal accuracy (typically 2–3× the horizontal error). The barometer provides far more accurate and responsive elevation readings — important for metrics like total ascent, ClimbPro profiles, and VAM (vertical ascent rate).
GPS elevation is used only as a long-term reference to correct for barometric drift caused by changing weather pressure during extended rides.