Apple Watch 4 GPS Accuracy (44mm Nike Edition)

[caption id="attachment_15588" align="alignright" width="145"] Test Route[/caption] I've done my GPS 'test' on the Apple Watch 4 (44mm Nike Edition). The Apple Watch 4 (AW4) uses GLONASS as well as GPS but let's call it GPS as no-one knows what GNSS means, except you clever lot reading this ;-) . The even cleverer ones amongst you will point out that the GNSS chip is GALILEO compatible, so the Apple Watch 4 is probably using that as well. The results OF THIS ONE TEST are very interesting and unusual, if I may say so. I'll hold fire until a later review/post with my overall verdict based on lots more runs/rides but here is my commentary on the formal test result from today. It scored 77% using the standard workout app That's pretty much the same as a good Garmin on a good day. 'Normal Good' but not in the same league as the V800, Ambit, Coros Apex 46mm or a Spartan Trainer - also on a good day. There is some subjectivity in this test and I was perhaps very slightly erring on the harsh side of fair - being kinder it would have scored 79%, so no material difference. The overall distance was under-reported by the AW4 by just over 1% and I typically find that almost all devices are accurate to within +/- 1% over this 10-mile route. So when something strays out of that +/-1% range then something unusual may be going on. Looking at some of the specific segments of the test, the Apple Watch did very well in easy GPS reception conditions and fared less well when the GPS-going got tough. Nothing unusual there. >> DETAILED TEST RESULTS SPREADSHEET AND SOURCE FILES HERE << But there is something strange going on with the GPS track. Dcrainmaker picked this up to a degree in his nice sports-focussed review of the AW4 (link to: dcrainmaker.com) when he noted that the Apple Watch cuts corners. I thought, when I read the review, that there may have been some special use-cases that caused this. But no. I agree with what he says, it does cut corners. Sometimes not by very much, sometimes by 'quite a bit', but it does cut them consistently. That could explain the under-reporting of distance. Perhaps. Let's park that thought for a minute. Take a look at this segment of the test. [caption id="attachment_32725" align="aligncenter" width="970"] [/caption] The Apple Watch 4 is in green (Ambit 3 in blue, Coros Apex in red). Apart from the detour into the river, the Ambit is probably spot on for the circle. Except it's not a circle it's a square. Yet the Apple watch has turned this into a circle more so than any GPS device I've seen. Off to the left of the above image, there is an out and back with a fairly tight turn around a tree as shown next... The Apple Watch doesn't spot this at all and just assumes it is a simple out-and-back (green). The following image shows the Apple Watch cutting some corners. Fair enough, it happens. But look at the rest of the track, it is very, very smooth, almost perfect-looking. And that same apparently perfect smoothness is typical of most of the rest of the track. But it can't be perfect, can it? Because it clearly cuts those two corners (and more besides) So I'm pretty sure that the Apple Watch is doing some manipulation of the GPS track here. It's either smoothing the raw data it gets and/or adjusting the GPS track based on its inbuilt motion sensor (a bit like Suunto's FusedTrack but on a finer scale). [caption id="attachment_32757" align="aligncenter" width="868"] Random selection of 15 seconds of data, shows different GPS values per second.[/caption] The upshot of all of this is that the Apple Watch 4 may be a little bit 'smoke and mirrors'. The GPS track looks really, really good. It's deceptively smooth and deceptively close to where you've been - but not quite close enough. It almost fools you into thinking it's awesome. But it's not. It's on the good side of average just like Garmin. A final point on the smoothness of the track. I have seen a similar smoothness in Garmin devices that use GALILEO (and GPS and GLONASS). Possible consequences Those of you wanting accurate distances could be disappointed Those of you wanting good running pace on the AW4 might actually have some luck because of the excellent smoothing. I'll dig into that later. Those of you wanting a sweet-looking, post-run GPS track will be super-happy. That's my 2 cents worth. Thoughts? Corner cutting when cycling too (yellow). And some of that corner-cutting makes the track out by MORE THAN 5 METRES which we would normally call FAIRLY BAD. Just sayin' : [caption id="attachment_32701" align="aligncenter" width="930"] , Apple (Yellow), Wahoo (Green), Garmin 935 (Red)[/caption] PS: The test was conducted WELL AWAY from my smartphone...about 2 miles away. PPS: Apple watch can be calibrated for distance (Source: apple.com). This is PROBABLY not relevant to what I am doing here, although if they are massaging the GPS points based on accelerometer readings then it might be relevant. I am totalling the distance from the recorded GPS points in 3rd party software (consistent to all my other previous tests). My other tests typically record GPS-only and GPS+GLONASS if GPS-only is unavailable (as in this case) so it is consistent for me to exclude as much 'fancy stuff' as possible. PPPS: My first run after this was with the STRYD app using effectively 1Hz recording (1 GPS point per sec). That track is not as good. The track is more jagged. It *DOES* make a better attempt at sharp corners and does NOT cut the corners BUT much of the track with STRYD's app is away from where it should be when compared to that produced by the Apple workout app. Edited: Version 1.02 amzn_assoc_tracking_id = "the5krunner-20"; amzn_assoc_ad_mode = "manual"; amzn_assoc_ad_type = "smart"; amzn_assoc_marketplace = "amazon"; amzn_assoc_region = "US"; amzn_assoc_design = "enhanced_links"; amzn_assoc_asins = "B07HDHLPBM"; amzn_assoc_placement = "adunit"; amzn_assoc_linkid = "7fa7112d4864e93029b146b57ad0411a"; amzn_assoc_tracking_id = "the5krunner-20"; amzn_assoc_ad_mode = "manual"; amzn_assoc_ad_type = "smart"; amzn_assoc_marketplace = "amazon"; amzn_assoc_region = "US"; amzn_assoc_design = "enhanced_links"; amzn_assoc_asins = "B07K3HLMTF"; amzn_assoc_placement = "adunit"; amzn_assoc_linkid = "ff8f84be6733feda9f0f06a1dbbc310f";