I would actually prefer to not have any GNSS (GPS) receiver in the smart glasses in order to keep the weight down and battery life up. GNSS receiver can still be in a wrist device and just use the smart glasses as a display linked via ANT+.
GNSS accuracy is poor in forests, canyons, and dense urban environments due to line-of-sight obstructions and multipath reflections. The latest Navstar Block III satellites should improve that a little, but any real solution would require deploying additional satellites in geosynchronous orbit like the Japanese QZSS.
> any real solution would require deploying additional satellites in geosynchronous orbit like the Japanese QZSS.
There's nothing about geosync orbit that would help with the tree/canyon effect. Satellites directly overhead contribute the least to horizontal positioning - essentially only helping to establish the "true" clock value but not 2D position.
Multi-constellation tracking can be helpful, simply because there are more satellites to use.
None of that is relevant to how QZSS actually augments GPS accuracy. Real world tests show that it works better than just using more constellations in lower orbits.
> GNSS accuracy is poor in forests, canyons, and dense urban environments
I feel like this should be solvable on the software side, especially for medium or long distance runs. If I look at the traces, I can see that the recorded zig-zag is obviously wrong, and a bit of smoothing should be able to fix it.
Most fitness trackers do apply some level of automatic track smoothing but it's not a solution. Sometimes athletes really do zig-zag around, especially on trail runs in rough terrain. The Apple Watch is sometimes overly aggressive about track smoothing which leads to funny results showing the athlete running through solid obstacles.
Accelerometer, magnetometer, and gyroscope sensor data can help a little to sanity check GNSS inputs and fill in brief gaps. But those tiny sensors have terrible drift which makes them nearly useless for sustained position tracking.
I run in New York City using a Garmin (Forerunner 935 but the model doesn't really matter). GPS accuracy is terrible in midtown due to the signal bouncing off the buildings. Sometimes it records that I've run a two minute mile. At a minimum you'd think they'd have software that can detect that it's unlikely I'm setting a world record (or scaling the side of a building).
This frustrated me enough that I eventually got a Stryd footpod. The pace/distance tracking is extremely accurate and I use it to override what the watch records. So the GPS track still bounces all over the place but the recorded pace/distance data is correct.
GNSS accuracy is poor in forests, canyons, and dense urban environments due to line-of-sight obstructions and multipath reflections. The latest Navstar Block III satellites should improve that a little, but any real solution would require deploying additional satellites in geosynchronous orbit like the Japanese QZSS.