[shiroiushi]

You're not going to get 100% confidence with either problem. The GPS one might be easier to get high confidence with, but even here you have to worry about 1) the accuracy of the GPS coordinates from your camera/phone, which isn't that good, and 2) calculating the exact boundaries of the park from the public data. So you could probably calculate with nearly 100% confidence that you're, for example, within 5km of a park, but if you take the photo from a location close to the park's boundary, the confidence will go way down. If you're a meter or two from the boundary, forget it.

[vinibrito]

How could the gps position and the park boundary not be exact? Phones GPS give a 2 meters accuracy, and a park boundary is a well defined hard line polygon.

Being close to the border changes nothing, I can just add a buffer outwards the park polygon to account for that. Asking because I'm afraid I may be missing something here due to this being something I already worked on.

[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.

[emj]

If you need to know 100% that the bird is in the park at that precise moment it can be tricky. If you need to identify a Bird-of-prey in the Alpha quadrant you can understand the Klingon proverb a sharp knife is nothing without a sharp eye.

[vincnetas]

What does it even mean "YOU are in the park". What is YOU? If you standing on the boundary, are YOU in or out? Details mater :D

[shiroiushi]

Exactly! What if you're standing on the boundary, with one foot inside and the other outside? These specifications are far too vague.