Is manual GPS activation normal for Apple Watch Ultra 3 outdoor activities?

GPS should be automatic as long as Location Services are on. Which they should be by default.

On the Apple Watch Ultra: press the digital crown, open Settings, go to Privacy & Security, and select Location Services to make sure it is toggled on.

Not having exact location data could certainly give you a poor estimate for your run. The only way to be sure is enable better quality data and test again.

However, you also need to be slightly cautious about the reported error unless you have something like a properly measured route as reference.

ShameemRussool wrote:

Thanks Steve!

One more thing, I used my watch for a running workout without location activated (so no GPS). Distance covered was inaccurate. There was an underestimate of 300m. Is that due to the fact that the GPS was off ?

I think so. How does it figure out where you are and how far you are going without GPS? It does have other measurements but they are much less accurate than GPS. For instance, motion of arms indicates taking steps walking or running, and there are accelerometers, but those methods are much less accurate. A pedometer on the leg would be much better than a sensor on the wrist.

And I agree with Branta -- people sometimes report an inaccurate result from a watch or something else, but how do they know what the "truth" actually is? I have measured some routes carefully with separate Garmin devices (that use GPS) and also just driving in an automobile to see how precise different sensors are for measuring distance. For a 25 mile bicycle ride, my watch agrees with the Garmin bike computer to within 0.01 mile or so. Which is about 50 feet, or 15-20 meters. I think most of the difference is due to the slightly different auto stop and auto start triggers on the different devices, e.g. at stop signs, traffic lights, the devices don't stop and start at exactly the same time so differ by a few feet maybe each stop/start.