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Reverse geocoding is hard

shkspr.mobi

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Re: Reverse geocoding is hard

#21

Post by Propelloni »

morkalork wrote: post #6

If I were giving directions to another human and not using house addresses I'd say something like "Queen street about half way down the block between Crawford and Shaw"

Fascinating to read. Around here people would do something like "follow the road (hand pointing down the road) at the first t-crossing turn left into a smaller road (hand pointing in the meant direction) continue for, I don't know, a few minutes. On your right (hand shows the meant direction) you'll see the park. A road comes up on the left and directly opposite of it is an entrance into the park. Go into the park and follow the path until you reach the first crossing. Turn left (hand shows meant direction) then follow until you reach the end of the park. The park should make a right turn there. The bench should be to your left."

Rarely if ever do people use road names to direct pedestrians, or car drivers. I guess, the people don't know them. I wouldn't.

Re: Reverse geocoding is hard

#22

Post by AlotOfReading »

Dachande663 wrote: post #13

Fun fact that was dredged up because the author mentions Australia: GPS points change. Their example coordinates give 6 decimal places, accurate to about 10-15cm. Australia a few years back shifted all locations 1.8m because of continental drift they’re moving north at ~7cm/year). So even storing coordinates as a source of truth can be hazardous. We had to move several thousand points for a client when this happened.

GPS coordinates actually account for the motion of the Earth's tectonic plates. The problem is that it's a highly approximate model that doesn't accurately reflect areas like Australia very well.

There's a great visualizer of the coordinate velocity from the Earthscope team:

https://www.unavco.org/software/visualization/GPS-Velocity-V...

Re: Reverse geocoding is hard

#23

Post by davidmurdoch »

punnerud wrote: post #17

I created this to solve my own need for reverse geocoding: https://github.com/punnerud/rgcosm (Saving me thousands of $ compared to Google API) Uses OpenStreetmap file, Python and SQLite3. First it finds all addresses using +/- like a square from lat/lon, then calculate distance based on the smaller list (Pythagoras), and pick the closest. It expands until a set maximum if no address is found in the first search.

Just curious if you looked into using S2 cells for this? It's what Pokemon Go uses for its coordinate system. http://s2geometry.io/devguide/s2cell_hierarchy.html

Re: Reverse geocoding is hard

#26

Post by sinuhe69 »

Not my area of expertise, but is this not a form of perfectionist problem? I mean, most places have a clear and simple address. For the rest, either a human can solve it, or we can make a few examples and let an AI do the work. We can go back to them later and revise them if we need to. Addresses don't change often, so I think things can stay the same for a long time.

Except for emergency dispatch and a few high-profile use cases, you can have a good enough address to let the user find its neighbourhood. But they still have the GPS or other form of address coding, so they can find the exact location easily. I'd say 99.9% of the cases are like that. The rest can be solved quickly by looking at the map!

Re: Reverse geocoding is hard

#27

Post by modeless »

vintermann wrote: post #14

Genealogy applications run into this a lot. The person of interest lived at Engeset. FamilySearch has geocoded a place called "Engeset, Møre og Romsdal, Norway". So that's it, right? Not so fast, [there are at least 3 Engesets in Møre og Romsdal]( https://www.google.com/maps/search/Engeset/@62.3358577,6.225... ). But that's at least better than when it's some local place name which it's never heard of, and thinks sou…

Converting from a name/address to coordinates is geocoding. Reverse geocoding is mapping from coordinates to a name/address.

Re: Reverse geocoding is hard

#29

Post by xucheng »

Dachande663 wrote: post #13

Fun fact that was dredged up because the author mentions Australia: GPS points change. Their example coordinates give 6 decimal places, accurate to about 10-15cm. Australia a few years back shifted all locations 1.8m because of continental drift they’re moving north at ~7cm/year). So even storing coordinates as a source of truth can be hazardous. We had to move several thousand points for a client when this happened.

Can this be solved by storing a timestamp of the record along with precise GPS coordinates? Could we then utilize some database to compute the drift from then and now?

Re: Reverse geocoding is hard

#30

Post by edent »

sinuhe69 wrote: post #26

Not my area of expertise, but is this not a form of perfectionist problem? I mean, most places have a clear and simple address. For the rest, either a human can solve it, or we can make a few examples and let an AI do the work. We can go back to them later and revise them if we need to. Addresses don't change often, so I think things can stay the same for a long time. Except for emergency dispatch and a few high-prof…

I am deeply guilty of being a perfectionist!

Ultimately, I just want something which is a nice balance between being useful for a human and not so long that it is overwhelming.

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