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Not really related to the article at hand, but I've been on a bit of a Google Maps binge the past couple weeks. I learned a few interesting facts, blurry Israel
by squeaky-clean 5y ago
Not really related to the article at hand, but I've been on a bit of a Google Maps binge the past couple weeks. I learned a few interesting facts, blurry Israel being one of them.
Another strange thing I found that might not be super well known (I didn't know about it) is that all GPS data in China is offset by a nonlinear psuedo-random amount. If you turn on the satellite view in Google Maps and look at various cities in China, you'll see that the road and business overlay is off by anywhere from 50m to 500m. And the strangest thing is that it's not a consistent offset from place to place.
Turns out this is very intentional, and China uses a different geographic coordinate system than the rest of the world. WGS-84 is the most common coordinate system, but China uses GCJ-02, sometimes called Mars Coordinates. Part of GCJ-02 is an algorithm that obfuscates the results. So applying any GCJ-02 coordinate to a globe using WGS-84 coordinates gets distorted like a funhouse mirror.
It's easy to find open source libraries to convert WGS-84 to GCJ-02 and vice versa. But Google Maps doesn't do it, for political reasons I suppose? I've read that if you open Google Maps within China the mapping data is correct, but have no way to test that.
- js2 5y agoRecently, I discovered Street View sometimes captures car crashes: https://goo.gl/maps/kJdgWQUU3eUMReUE8 https://goo.gl/maps/kJdgWQUU3eUMReUE8 https://ibb.co/x18fy3s https://ibb.co/x18fy3s
- joering2 5y agoTwo years ago when I saw Google car in front of me about to pass, I sure as hell opened the window and give it a bird, Maverick style. And sure as hell some 6 months later punching the address of my encounter, there I was in my car, with blurred face showing a middle finger that was surprisingly not blurred. So I showed it to all my friends all proud and stuff. Sadly a few months later the photo was replaced by I guess another drive-by. I imagine for many reasons since they already have a car in place, I'm sure they take few takes when passing by and someone must have reported me.
- fy20 5y agoWell they knew the photo had a face, so maybe their algorithms simply prefer photos without people. There's plenty of reasons why you should prefer a photo of a location without a person, even if blurred - this being one of them!
- robotastronaut 5y agoNitpicky, but useful for anyone interested in spatial data: WGS-84 is not a "GPS standard" but rather a geographic coordinate system and is usually paired for consumption with a projection like wgs 84 web mercator to view those 3d coordinates on a 2d plane. Super interesting stuff and reconciling these standards across the globe is a really fun problem, and one you'll likely run into if you ever find yourself dabbling in remote sensing pipelines.
- squeaky-clean 5y agoI don't know if I would call it nitpicky for this example :P Thanks for correcting me, I've edited the comment.
- randomluck040 5y agoI’m also working in the field and the Friar thing that came to mind was https://ihatecoordinatesystems.com https://ihatecoordinatesystems.com haha
- qwertox 5y agoI hate them too. It's the worst to have to reproject an image or GeoJSON and overlay it onto a map. Very satisfying one you've managed to do it, but it's a pain nonetheless, at least if you don't work in the geospatial field and rarely use tools like GDAL.
- bebop 5y agoAn interesting tidbit is that our world is not a sphere, but a spheroid. This makes 3d -> 2d transformations very local.
- jrochkind1 5y agoMy memory says that US government GPS at one point intentionally introduced reduction in accuracy/resolution as well, but they stopped, which was part of what led to the commercial GPS revolution (along with cheaper tech of course). Let's see... Wikipedia seems to confirm: > During the 1990s, GPS quality was degraded by the United States government in a program called "Selective Availability"; this was discontinued on May 1, 2000 by a law signed by President Bill Clinton. https://en.wikipedia.org/wiki/Global_Positioning_System https://en.wikipedia.org/wiki/Global_Positioning_System
- tomerv 5y agoInteresting to note that the removal of selective availability enabled the creation of Geocaching ( https://en.wikipedia.org/wiki/Geocaching#History https://en.wikipedia.org/wiki/Geocaching#History ).
- yborg 5y agoIt also enabled the modern mobile navigation industry. I was working on automotive navigation systems in the early 90s and SA was a killer for the product, options were various dead-reckoning and inertial sensors or differential GPS, both of which ended up being cost-prohibitive. But you can't do usable route guidance with a 100m CEP in an urban area.
- londons_explore 5y agoWith modern high powered CPU's, more detailed maps, and particle filters (which require all that cpu), dead reckoning has become much more viable. I suspect you could go hours driving round a city with the GPS and WiFi location turned off before losing your position - simple wheel speed, gyro and compass is sufficient for most stuff.
- NickNameNick 5y agoYou'd also need to account for slope.
- captainmuon 5y agoI've found that the maps match the GPS of my phone exactly, but the satellite pictures are shifted. Does that mean: 1) My GPS module also gives out obfuscated coordinates when in China or 2) Google uses shifted satellite images?
- thaumasiotes 5y ago> I've found that the maps match the GPS of my phone exactly I can use OpenStreetMap fine in China. But that's not Chinese data. If a Chinese person sends me a location marker on WeChat, the marker will show up (for me, in WeChat) at some other, unintended, location; I can't use that feature at all.
- squeaky-clean 5y agoI wish I had saved some of the links I had found, one source I read said that the non-satellite map data was actually correct, and it was the stitching of the satellite imagery that was incorrect. I had no way to test this and no other source mentioned this, so I ignored it. But it's funny you mention this, #2 might be the case. robotastronaut also corrected me that it's not actually the GPS that is being obfuscated, but the map coordinate system. So your GPS device is probably receiving correct results, but on an improperly projected map.
- SECProto 5y ago> one source I read said that the non-satellite map data was actually correct, and it was the stitching of the satellite imagery that was incorrect The opposite is true: If you look at areas like the Macau-Zhuhai border or Hong Kong-Shenzhen, you'll see that the satellite imagery is continuous but the mapping data has discontinuities at the border (some zhuhai streets are halfway across the water to Macau!)
- gruez 5y agoNeither. The satellite images are accurate, and so is your GPS readout. What's shifted is the official data that the government provides (eg. location of roads). more here: https://news.ycombinator.com/item?id=10964450 https://news.ycombinator.com/item?id=10964450
- dirtyid 5y agoHave you checked out South Korea?
- varenc 5y agoSouth Korean on GMaps feel likes a snapshot of 2009. Whereas the rest of Google Maps has switched to something vector based, South Korea still has tiling based map images with different images for different zoom levels and the place names just baked into the image. Any idea why? Apple Maps is great in comparison.
- xxpor 5y agoIt's a similar law to what's discussed here. The justification is protection from NK.
- ncpa-cpl 5y agoCould it be a licensing issue? Naver Maps has really good street view and very accurate maps in SK. https://map.naver.com/ https://map.naver.com/
- xxpor 5y agohttps://www.google.com/amp/s/www.wsj.com/amp/articles/google-challenges-south-korea-over-mapping-restrictions-1463478584 https://www.google.com/amp/s/www.wsj.com/amp/articles/google...
- AYBABTME 5y agoMy reading of the situation is that it's a convenient "national security issue" which happens to favor SK companies and insulate them from having to compete head-to-head with Google Maps. Turn-by-turn navigation also doesn't work using Google Maps. Meanwhile SK navigation apps like Naver Maps or Kakao Maps have really poor navigation features if you compare to what you'd have using Google Maps on an American road. The end result is that consumers suffer, since artificial market protection leads to an inferior product and no real need to improve and compete by players on the local market.
- azidemakes 5y agoWhen I last went in late 2018, it was not corrected for on the satellite maps. Google maps was still usable for walking directions, however.
- CaliforniaKarl 5y agoIndeed, there's a Half As Interesting video talking about this: https://www.youtube.com/watch?v=L9Di-UVC-_4 https://www.youtube.com/watch?v=L9Di-UVC-_4
- mayli 5y agoSee the explanation on Wikipedia: https://en.wikipedia.org/wiki/Restrictions_on_geographic_data_in_China https://en.wikipedia.org/wiki/Restrictions_on_geographic_dat...
- ryandrake 5y agoMy understanding is that all agreements with Chinese map data providers require that map software implementors only display data projected into the "obfuscated" coordinate system, and the agreements forbid un-projecting back into "real world" WGS-84, regardless of how simple the algorithm is. So, it's more of a business agreement and less of a political thing, but with China there isn't much of a difference.
- freewizard 5y agoWhat I learned a few years back about this is the official (un)obfuscating implementation was distributed to licensed companies in binary .dll/.so/.a , and not allowed to be redistributed or reverse-engineered. Licenses are only given to local companies, and foreign companies may only buy service from them. That's why if you reverse engineer Google Map or Apple Map app, they all make real time API calls to do the conversion on servers. Those contracts may also limit the end user who can consume these APIs to be in China, hence foreign users will see the shifts of roads/etc. The open-sourced implementation one may find on the internet are probably thru sth like curve fitting by sampling many data points. It may have good enough approximations but may not work one day if the gov agency decides to change the algorithm. Changing algorithm is a backward compatibility hell but not a big problem for the industry actually, because most Map apps are owned by big corp which has resource and motivation to comply.
- xkcd-sucks 5y ago> distributed to licensed companies in binary .dll/.so/.a , and not allowed to be redistributed or reverse-engineered Such irony in CCP using licensing to protect their IP
- seniorivn 5y agoonly if you have misconception about what ccp and other one party states actually are
- mastazi 5y ago> you have misconception and what's the "correct-conception"?[1] I'm curious because I get what parent means in terms of intellectual property issues in China but I don't get what do you mean from your comment, especially the fact that you include "other party states" - is it some sort of general rule that you're hinting at? [1] funny, I just realised that there is no antonym of "misconception"
- leephillips 5y ago
- gsich 5y agoOpenstreetmaps works correctly.
- Tabular-Iceberg 5y ago> But Google Maps doesn't do it, for political reasons I suppose? Or whoever is in charge of importing the data simply doesn’t know that different coordinate systems is a thing. You’d be surprised how many GIS professionals are oblivious to this, especially ones in charge of things that tend to spill large amounts of oil into the environment when they get it wrong: https://www.maritime-executive.com/article/london-club-warning-over-reliance-gps https://www.maritime-executive.com/article/london-club-warni...
- systematical 5y agoI learned earlier today that the little google street view man nopes the fuck out of Kabal.
- neumann 5y agoReally silly question - but can't they correct for this without the GCJ-02 by just correlating the mutual of the map information with the satellite information? It seems like if you can have all the information provided to you, just randomly warped by some deliberate obfuscation you could 'trivially' (aka primitively) correct for it by using the available data of the satellite and the maps by feature matching and non-rigid registration? edit: updated silly question after reading more on this
- dodobirdlord 5y agoCircumventing the obfuscation is a crime.
- dehrmann 5y agoIn China? Is it a violation of the data source license?
- ajsnigrutin 5y ago> Turns out this is very intentional, and China uses a different geographic coordinate system than the rest of the world. WGS-84 is the most common coordinate system, but China uses GCJ-02, sometimes called Mars Coordinates. Part of GCJ-02 is an algorithm that obfuscates the results. So applying any GCJ-02 coordinate to a globe using WGS-84 coordinates gets distorted like a funhouse mirror. A lot of countries use their own coordinate systems, that make their countries look flat on a x/y plane. Eg. my country - slovenia. Usually those coordinate systems are easy to calculate to wgs84 or web mercator projection[0], compared to the chinese solution [0] https://en.wikipedia.org/wiki/Web_Mercator_projection https://en.wikipedia.org/wiki/Web_Mercator_projection
- baybal2 5y ago> But Google Maps doesn't do it, for political reasons I suppose? FYI: Google has never really quit China. It has running offices in Beijing, Foshan, and, recently, Shenzhen.
- ipv6ipv4 5y agoI can't wait for the BBC to publish an article about the inaccuracies in China ...
- supernova87a 5y ago>I learned a few interesting facts, blurry Israel being one of them. Yes, Israel specifically has favor from the US government that satellite imagery of that country is allowed to be blurred: https://en.wikipedia.org/wiki/Kyl%E2%80%93Bingaman_Amendment#:~:text=The%20Kyl%E2%80%93Bingaman%20Amendment%20(KBA,outside%20of%20the%20United%20States https://en.wikipedia.org/wiki/Kyl%E2%80%93Bingaman_Amendment....
- duckmysick 5y agoThe BBC article in the submission mentions this restriction and the Kyl-Bingaman Amendment.
- andi999 5y agoIsnt it that all google services are not available in china, so it might not be possible to use google maps inside china.
- fps_doug 5y agoWhen it still was available they had a license, but only when using Google Maps in China.
- camillomiller 5y agoCan confirm, the map in China is correct, but completely useless. Most addresses are not recognized or easily mistaken for other similar ones. Plus, the entire layer of business and POI listings that give GMaps its competitive edge are not there. It feels like using a foldable paper map.
- nroets 5y agoAll Google products except the Google Translate App are blocked in China. So no Google maps. I spent 2 months cycling China from Hong Kong to Beijing. Despite only using Chinese characters, Baidu maps worked very well for me. I copied the characters I needed (Hotel, supermarket) into it from the translator. Here's my journal https://www.cycleblaze.com/journals/5000years https://www.cycleblaze.com/journals/5000years
- Insanity 5y agoReally nice photos, must have been quite the trip!
- woutr_be 5y agoRegarding the “foreigners can’t stay here”, from what I know, this is because it requires extra work for hotels, they need to report your stay to the local police station, so usually smaller hotels, or the ones in non touristy cities just don’t do that. (And I believe that any tourist, needs to report their address to the local police station within a few days)
- 3v1n0 5y agoSomething similar happens in Cuba as well. There are cheaper places where only locals can go (and till some years ago, also the other way around was true)
- runarberg 5y agoWow, I travelled in Cuba in 2007 and I was completely unaware of this. I was aware of the double economy and how there are some buses that the locals don’t use and vis-versa (same is true in my country; in both cases it is more about price and convenience then access). But hotels for locals only completely missed my attention.
- doublepg23 5y agoAny info on how you setup your Cuba trip?
- mavhc 5y agohttps://www.google.co.uk/maps/@42.4300052,130.6278764,3096m/data=!3m1!1e3 https://www.google.co.uk/maps/@42.4300052,130.6278764,3096m/... China's roads appearing to cross into Russia. https://goo.gl/maps/oDwCuGhxxZVSj7nJ6 https://goo.gl/maps/oDwCuGhxxZVSj7nJ6 Hong Kong/China border bridges
- neycoda 5y ago> China uses GCJ-02, sometimes called Mars Coordinates. Part of GCJ-02 is an algorithm that obfuscates the results Why would a space agency use a coordinate system to obfuscate results on another planet?