This app was designed to answer my wife’s question “what country would we hit if we went straight” (generally posed while pointing her phone)

But with two additional twists:

1. It loads up historical maps from different years (right now 1 BC, 700 AD, 1000 AD, 1300 AD, 1800 AD, 1900 AD) so you can see what you would hit if you had a time machine AND you went in the direction your phone is pointing

2. Tap a country/territory for an (AI-generated) blurb on what you are pointing at

How it works: Starting from your phone’s bearing, we trace the great-circle in 200 km steps, prefilter candidate countries with bounding boxes (~5–10 instead of ~200), then check ~20 km points along each segment to catch coastlines and stop when the path first enters another country.

Great-circles (https://www.movable-type.co.uk/scripts/latlong.html) are why you can hit Australia from NYC, even though when you look at a flat map that can be hard to see.

There might be some weird stuff in the explanations, I haven’t read all 1,400 of them. If you see something weird let me know and I will update it!

The app is free and doesn’t have ads or tracking — your location and bearing are only used locally to figure out where you are and what you’re pointing at

Probably will work best if you hold your phone pretty flat :)

Thank you to André Ourednik and all the contributors to the Historical Basemaps project: https://github.com/aourednik/historical-basemaps)

Very neat! I was confused as to how the possible paths would lead me to France, or if I slightly moved my phone, Brazil. Then I remembered French Guiana - it might be worth adding awareness of things like overseas departments rather than just the parent country.

Also, it reminds me of this HN conversation I found fascinating a few years back: Finding the longest straight line you could sail without hitting land - https://news.ycombinator.com/item?id=16965650

This question ate away at me too, and I also scratched the itch: https://mrgris.com/projects/landfall/

Specifically mine deals with what you'd hit looking across the ocean from a coast. I had long wanted to make mine an interactive app but could never fully motivate myself to do it, so congrats for shipping.

This is cool! Immediately upon playing with it I find I want more features :-)

- Ability to toggle ocean traversal off/on

- Ability to see route on a map

- AI generated summary of the trip if I took it -- what things did I see along the way? (Should reference real map data, then make up a story; matching local culture etc.)

Very cool and fun!

The first thing did when I opened it was to point my phone at the floor though, trying to find Australia. Took me a moment to realise it wasn’t that kind of pointer!

I was on vacation in Baja Mexico. South of California. We were having dinner on the beach and my wife asked "I wonder how far you can go before you hit land".

Later some basic Geo calculations and a Google maps visit to estimate the bearing she was looking and yeah, the great circle arc went all the way to Antarctica, crossing half a planet.

Its remarkable how huge the Pacific Ocean is. Its Vast.

This seems to be from the same universe as the excellent https://pointerpointer.com/

Maybe you can do this with other things too. For example cities, buildings (clubs, shops, etc) or even people.

I think about this sometimes, so I like the idea, but how do you define “straight” on an oblate spheroid? Great circle, constant direction (e.g. “due east”), or something else?

I suppose the heading error from the compass is so large there is little reason to use the real geodesic (https://link.springer.com/article/10.1007/s00190-012-0578-z) as opposed to the great circle

Neat! I think I found a bug though? I'm in Southern Germany, and for some direction south of me it showed me Italy, which doesn't border Germany, I think

edit: As a wild guess, it might have something to do with scanning resolution? Austria's western "arm" is only about 40 kms across

This actually took a while to grasp the concept of. Where I'm living (so far from the coast that it might as well be landlocked) it took a while of eyeballing on a map, but I did find one angle where it's not kinda common sense where I would land. I suppose this is a lot more fun if you live near the coast and the answer is not completely obvious to anyone who knows the neighboring countries.

Cool!

One of the countries in 1800 renders as “M?ori” for me, so it looks like you have some kind of character encoding issues (or there’s some language I don’t know about where ? is a letter).

Feature request: is there a way to get a blurb about one’s current country? Lots of people on this site will get “Viceroyalty of New Spain” (the pre-independence name of Mexico, which included the entire current American Southwest incl. California and Texas) when they switch to 1800 and might want to learn more about it.

I love that you can set the date. Apparently I'm looking at where the "plateau fishers and hunter-gatherers" were at 1 BC.

I'm very confused. I'm in Boston, and if I face 270, I get Canada, but if I face 269.9, I get Mexico.

I feel like there should be something across the Pacific between Canada and Mexico.

I wrote one of these but it only works for residents of san marino

This is incredible timing as I was having my own version of this question with family last week!

your app company name of Gross National Products made me smile. well done!

Very cool, me and my kids been playing and enjoying it. Nice work!

Does this take into account the fact that the Earth is not a perfect sphere?

Installed it, love it.

It’s a 30 second novelty I’ll show to friends.

It would be great if the line continued rather than stopping g at the first country.

For example which direction is Japan? I think it might be behind Papua New Guinea.

Some country with Muslims squatting there.