[shiroiushi]

>Phones GPS give a 2 meters accuracy

Well I already pointed out that if you're within a couple meters of the boundary, you won't have good confidence because of this fact.

>and a park boundary is a well defined hard line polygon.

Is it? I'm no expert on parks, but surely some of them have borders along rivers. Many US states have such borders.

>Being close to the border changes nothing, I can just add a buffer outwards the park polygon to account for that.

That doesn't account for the 2m accuracy. What if I'm standing exactly 1m from the boundary when I take the photo? You have no idea if I'm really in the park or not from the GPS data.

I also have serious doubts about your 2m accuracy claim, based on personal experience. Maybe if you're standing in a wide-open desert with nothing around you, but anywhere else, the accuracy isn't that great, especially around buildings. GPS accuracy is terrible in cities.

[ddoeth]

> Is it? I'm no expert on parks, but surely some of them have borders along rivers. Many US states have such borders.

Depending on the country, but Australia has some [1]. I still think that there is a set of polygons that can be used to describe this border.

Not to argue against your point (I rarely get less than 4m of accuracy), but luckily

> but anywhere else, the accuracy isn't that great, especially around buildings. GPS accuracy is terrible in cities.

cities are (almost?) never in national parks.

[1]: https://www.nationalparks.nsw.gov.au/-/media/npws/maps/pdfs/...

[shiroiushi]

>cities are (almost?) never in national parks.

Sometimes they are. See Washington, DC.

Anyway, the requirement is for determining if a photo was taken in a park or not. The resolution wasn't stated, however: just how accurate do we need to be? If I'm in a canoe in a river that borders a park, but the river isn't part of the park, but the shoreline a few meters away is, our algorithm might claim I'm in the park, when I'm really not. The requirement wasn't "somewhere near a park", but "in a park". Rivers change their courses over time, so some polygons aren't going to accurately describe this border.

[ric2b]

Let's be real, GPS is much more accurate than whatever boundary for the national park that someone might come up with, where the park starts is really ambiguos unless there's a physical man made divisor like a fence.