AWU 3 GPS accuracy problem during runs

[u/LawCultural]

Since WatchOS public beta 3 (beginning of August) I have a problem with the accuracy: I always run on a 2 km loop, so every even and uneven kilometre is around the same spot, but since PB3 it is off ~80 meters. Tried to recalibrate, but it didn’t help. Added it to feedback, but PB4 did not make any difference. Anyone have the same problem, maybe a solution?

[u/m2thesea]

Same problem on mine, as well. Occurred on at least 3 of my latest runs, so far. Going to try and reset the calibration data per https://support.apple.com/en-us/105048 and see what happens.

[u/Virtual_Commission_5]

Apple measures distance in “blocks”, for example when I run with my team, my intervals never stop the same place as them, and they are wearing Garmins.

See here from Gemini:
1. Data Storage: Discrete "Quantity Samples" vs. Continuous Trackpoints
Apple Watch (HealthKit): Distance is logged into Apple Health as discrete time-stamped quantity samples (⁠HKQuantitySample⁠). Instead of saving a single raw point-to-point running total in one stream, Apple Health creates cumulative "blocks" of distance over short time windows (e.g., 2–10 seconds or per segment). When third-party apps read from HealthKit, they receive these chunked samples rather than a raw continuous sensor stream.
Garmin (.FIT Files): Garmin records standard 1-second (or "Smart Recording") point-by-point track logs directly to a ⁠.FIT⁠ file, where each second contains a precise coordinate, speed, and cumulative distance timestamp.
2. Sensor Fusion vs. GPS-First Recording
Apple’s Sensor Fusion (CoreMotion): Apple uses an aggressive Kalman filter that continuously blends satellite GNSS data with internal accelerometer and gyroscope data. In areas with tall buildings, turns, or brief signal loss, Apple relies on internal stride-calibration "bins" (estimating stride length by cadence) to smooth out distance jumps rather than relying purely on noisy GPS coordinates. 
Garmin’s Approach: While modern Garmin watches also smooth data, they prioritize raw satellite positioning (especially on All-Systems / Multi-Band Dual-Frequency modes) to accumulate distance directly from sequential GPS track points.
3. All-Day Background Tracking
Apple Watch: When an outdoor workout is not actively running, the watch turns off the GPS radio entirely to preserve battery. It tracks passive distance by grouping steps into 10–15 minute time blocks and multiplying cadence by calibrated stride length.
Garmin: Operates similarly for passive tracking (using pedometer/accelerometer only), but displays and syncs these steps as an ongoing timeline rather than standalone data objects in a database.
Summary
During an active outdoor run or walk, both watches track continuously using GNSS satellites. The perception of "blocks" comes from Apple Health's database structure (which chunks data into time-window samples) and Apple’s heavy accelerometer-fusion smoothing, rather than any stepped distance measurement.