Not my link. I do not know anything about a Valencia Marathon study. Did that study share the number of observations for each device type, the mean for all device observations, and the standard deviations? If the author does not understand statistical analysis, there is a pretty strong likelihood that the presentation is not statistically relevant.
I do know that my Garmin watches (multiple) are an order of magnitude more precise than my personal Apple devices. This is based on hundreds of runs and comparing standard deviations between the two types. I believe that the design of fellrnr's analysis is flawed in that it looks at individual activities in a way that exaggerates absolute GPS position errors that wash out over an entire activity. And, they virtually vanish when looking at many activities over time.
I do know that my Garmin watches (multiple) are an order of magnitude more precise than my personal Apple devices. This is based on hundreds of runs and comparing standard deviations between the two types. I believe that the design of fellrnr's analysis is flawed in that it looks at individual activities in a way that exaggerates absolute GPS position errors that wash out over an entire activity. And, they virtually vanish when looking at many activities over time.