from Hacker News

What happens to Google Maps when tectonic plates move? (2020)

by dmitrysergeyev on 3/23/24, 8:36 PM with 79 comments

  • by perotid on 3/24/24, 12:34 AM

    FWIW, global drift vectors by NASA: https://sideshow.jpl.nasa.gov/post/series.html

  • by twelvechairs on 3/24/24, 11:18 AM

    For those looking for a clearer standard it's the International Terrestrial Reference System and Frame [0]. The better datums in use today are tied to a particular year (epoch) reference frame of this.

    For instance Australia's GDA2020 [1] is based on ITRF2014 at epoch 2020.0. It replaced GDA94 which was based on ITRF1992 at epoch 1994.0. The difference is around 1.8 metres

    [0] https://en.m.wikipedia.org/wiki/International_Terrestrial_Re...

    [1] https://www.ga.gov.au/scientific-topics/positioning-navigati...

  • by latchkey on 3/23/24, 10:46 PM

    Discussions on similar submissions:

    What Happens to Google Maps When Tectonic Plates Move? https://news.ycombinator.com/item?id=22146454 (January 25, 2020 — 2 points, 0 comments)

    What happens to Google Maps when tectonic plates move? https://news.ycombinator.com/item?id=22145303 (January 24, 2020 — 188 points, 53 comments)

    What Happens to Google Maps When Tectonic Plates Move? https://news.ycombinator.com/item?id=12216474 (August 3, 2016 — 2 points, 0 comments)

  • by politelemon on 3/23/24, 10:46 PM

    If you want to dive even deeper into datums around the world, there's a site dedicated to it: https://www.asprs.org/asprs-publications/grids-and-datums

    You'll find many countries in there with a bit of history of their datums and how they arrived at their present state. It's a dry reading that can be fascinating at the same time.

  • by hnburnsy on 3/23/24, 10:53 PM

    Well since the author did not talk to Google we will not find out by reading this article.

  • by jraph on 3/24/24, 9:52 AM

    I wanted to know how it's handled on OpenStreetMap, and here's how [1], on a first of April anyway.

    If someone knows more on this, don't hesitate to share :-)

    [1] https://blog.openstreetmap.org/2017/03/31/osm-plate-tectonic...

  • by fy20 on 3/24/24, 2:34 AM

    The article doesn't mention it, but how are the coordinates of property boundaries recorded in South California to take into account the drift?

    In my relatively tectonically stable country there is a single coordinate system for the whole country.

    I'd imagine you need to record distance to a local landmark or similar? And what happens when there are shifts that end up in roads split in two like in Turkey last year?

    https://nationalpost.com/news/world/turkey-syria-earthquake-...

  • by epivosism on 3/24/24, 7:38 AM

    I often think about a scifi story where after X million years, somehow familiar humanity survives, and two plates containing land with VERY different natural flora and fauna approach each other - for example, california, home of many native plant defenders, and australia. As they get closer than 50 miles, news would start to mention making sure not to cross-transplant animals and plants. Under 20 miles, the wind and storms would do some work already, but people on both sides may still be resisting. But the moment they actually touch for the first time, some great treaty may shimmer into enforceable existence, changing the future of that whole world.

    Or else, they'd just build fences, forbid anyone from living on the coast, and maintain this artificial continental boundary forever...?

  • by dhosek on 3/24/24, 2:03 AM

    I remember having a hand-held Garmin GPS unit back in the '00s that I used on a trip to Berkeley from Los Angeles (one bonus was that the speedometer in my car didn’t work¹ so I was able to use it as a speedometer for the trip). The location that it showed on the map was consistently off by about 50 feet. I wonder now if this was a tectonic drift or just an inherent inaccuracy of the unit.

    ⸻

    1. When I think back to that car, it’s amazing what a piece of junk it was. On the other hand, it was a convertible, so a lot of fun although my wife considered it a deathtrap.

  • by aloer on 3/24/24, 11:01 AM

    Fun facts I remember from looking into this in university some 9 years ago:

    It’s not only the sideways movement of plates that causes a shift.

    WGS 84 and other reference systems work with an underlying ellipsoid reference model. This ellipsoid is chosen to approximate the earth surface but it’s a simple shape and as such can’t account well for things like mountains and other irregularities in the shape of the earth.

    Not only does that mean that your position on a mountain is less accurate, it also means that it becomes less accurate over time due to mountains growing.

    These of course are tiny numbers so compared to a few cm shift of the plates it is nothing.

    Another fun fact is that the ellipsoid also grows more inaccurate over time due to the earth rotating around a fixed axis.

    The rotational force slowly causes the earth to flatten at the top and bottom (where the poles are) and to widen in the middle.

    This too I assume is negligible

    Speaking of ellipsoid, today I think it is measured via satellite. But in the past things had to be done by hand and were more local in nature. There’s a lot of history here as well since mapping has always been a very important task for governments.

    So today in a lot of places a lot of data is still based on systems other than wgs84. Either because it’s historical data (e.g. property boundaries before gps was invented), or because they use a more localized reference system including a more localized ellipsoid that better matches specific country or state needs.

    Perhaps one day we will use a big world wide look up table instead of a mathematical representation of the earth shape.

    What I did at university was to compare a Germany-wide lookup grid with the mathematical approach of a Germany-wide reference system.

    This lookup grid was created by a state agency and was more accurate because it could include more localized reference systems. In technical terms think of this as a pre calculation where each state can choose its most accurate method and then the results are put together into a country wide lookup table.

    Last fun fact: The result of this comparison showed that the difference of a German-wide reference system compared to this collection of state-wide reference systems is up to four meters.

    Edit: removed word inaccuracy, added difference. It’s all relative. What it mostly shows is that when working with geo data you need to know what source and what target reference systems to use. Otherwise things break

  • by 082349872349872 on 3/24/24, 7:32 AM

    Assuming 30cm/pixel and O(75mm)/year plate motion, a several year update cycle ought to suffice for visual purposes (how frequently does Maps refresh now, anyway?)

    https://news.ycombinator.com/item?id=39770836

  • by Waterluvian on 3/24/24, 3:16 AM

    Resurvey and publish a new datum. We’ve been doing it for a long time. This is fascinating stuff though because WGS84 predates this era of popular web map usage.

  • by the-rc on 3/24/24, 12:03 AM

    They update the data on a regular basis, like they had to do in Japan in 2011 after the tsunami. They even flew planes to capture imagery in the immediate aftermath.

  • by beefnugs on 3/24/24, 12:44 AM

    Well up in canada we have 5 year old google street data, and nobody even updates business hours on 80k+ cities...

  • by bgro on 3/24/24, 11:38 AM

    I’ll have to add this to my long list of technical problems when people request a teleporting super power.

    Some related problems are the planet’s location in orbit / the solar system’s location relative to the entire universe and how landscape changes over time (trees/towns/mountains/rivers appearing and disappearing).

    On another related note, it’s worth noting that the ability to pause time is a universe-ending super weapon. Even if it worked like you intended, you wouldn’t be able to use any senses or breathe without moving.

    Similarly, super speed would cause every human movement to have deadly force. You would go insane from the relatively slow action of everything operating at standard speed. TV might be hours per frame instead of frames per second, with incomprehensible audio to match.

  • by patcon on 3/24/24, 4:57 AM

  • by elatto12 on 3/24/24, 12:27 AM

    It's so crazy, never thought about this before

  • by tempodox on 3/24/24, 8:10 AM

    Google cancels the project?

  • by tucnak on 3/24/24, 6:41 AM

    > This screenshot represented my position in Google Maps while I was standing on my back deck.

    In the age of OSINT: not smart.

  • by ern on 3/24/24, 7:03 AM

    (2020)

  • by narven on 3/25/24, 2:34 AM

    google kills google maps

  • by aaron695 on 3/23/24, 11:42 PM

    The Australian tectonic plates move about 7cm a year, if you didn't adjust for it they'd be losing 2-5 thousand dollars a year as the fence moved in many suburban homes. Of course you'd gain it on the other side.

    Google needs to be dealing with it constantly, you'd be able to observe more errors on Google maps, ie. look at Google directions and how often mistakes are made, if it wasn't updated monthly? I'd guess yearly is not enough.

    Most of this article seems to be about other issues.