How Accurate is Strava vs Apple Watch vs Laser Rangefinder???

Educated as a Mechanical Engineer and trained as a Six Sigma Black Belt, I love data. Data is neither good nor bad. It is just data. And as long as it's collected accurately and properly, it cannot be refuted. You may like it or not, but that's a human emotion you attach to the data. There is just no arguing with data. It is what it is. Based on that, I wanted to know why my Apple Watch Ultra II, Strava, and my Sig Sauer rangefinder do not agree on distances... I have a thousand-yard range set up on my property. I know exactly how far 880 yards (one-half mile) are from the target to direct line of sight of my marker. Well, to within 1 yard (3 feet) as sighted by my Sig Sauer Kilo 2200 BDX rangefinder. This Kilo model is accurate to within 1.5 feet out to 500 yards and to within 3 feet (1 yd) beyond 500 yards. So when the rangefinder, using Lightwave DSP Technology, says my marker is at 880.1 yards, I believe that I ...