Hacker News Reader

Comment by squeaky-clean | Hacker News Reader

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.

View on HN

Nitpicky, 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.

I don't know if I would call it nitpicky for this example :P Thanks for correcting me, I've edited the comment.

I’m also working in the field and the Friar thing that came to mind was https://ihatecoordinatesystems.com haha

I 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.

An interesting tidbit is that our world is not a sphere, but a spheroid. This makes 3d -> 2d transformations very local.

What 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.

> 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

only if you have misconception about what ccp and other one party states actually are

> 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"

Not really funny, as nouns in general do not have antonyms.

Generally nouns prefixed with mis- do; sometimes you just remove the mis- part eg. understanding vs misunderstanding, management vs mismanagement etc.

You make my point. Your examples are not pairs of antonyms. Management is not the opposite of mismanagement.

Verconception? - truth, 7 hits on google. Orthoconception? - straight, also 7 hits. Benconception? - good, 80 hits off topic. What else...?

At least in science education, misconceptions are so vastly more common than correct conceptions, that it makes sense there's a compact negative form but not a positive one. /s

If you think you know better what the CCP is, why don’t you educate us?

Hey, I'll bite: they are a thousands-year old country who has seen nations like the US and protectionist strategies like IP law come and go for centuries. They probably know what the US is going to do before the US knows what they're going to do, and certainly before the US knows what CCP is going to do.

> they are a thousands-year old country

china, the ethnicity, is indeed thousands years old. CCP, however, is barely over 70 yrs old.

Nickpicking: the CCP foundational congress was held on 23 July 1921, making it 100 years old in a couple of month. The Red Army was founded on 15 July 1927, which is why it is generally assumed (seriously or not, I don't know) that China aims at reuniting with Taiwan before 2027.

But the CCP has been controlling mainland China for a little bit over 70 years, indeed.

to be even more correct, china isn't one culture or one ethnicity. it covers a huge area, and especially before modern times, it was composed of a lot of different cultures and ethnicities, with a shitload of different languages and customs. CCP and other earlier powers (Emperors?) just brought them all, or large chunks, under a common flag.

Most importantly, a common writing system, common to a huge area. One that mathematicians successfully took inspiration from and repeated the success of universality at an even greater scale.

Think bigger. There is cultural knowledge going back further than any particular political or economic system. China has seen those come and go within its own borders, too.

It is fun to see such a discussion - I've been working on my own implementation of de-obfuscating Mars Coordinates since January 2021 with very good results. And Yes, some curve fitting is involved.

At the end of the day they may obfuscate coordinates and blur maps, but the truth will eventually come out.

R tree

"they all make real time API calls to do the conversion on servers"

Can't imagine why anyone would want that to happen.....

You seem to be implying surveillance. I think the actual answer is "because if the library were downloadable, the algorithm used for military physical security would be quickly reverse-engineered."

My 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

Interesting to note that the removal of selective availability enabled the creation of Geocaching ( https://en.wikipedia.org/wiki/Geocaching#History ).

It 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.

With 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.

You'd also need to account for slope.

I’ll be overjoyed the day that the compass in the vehicle can tell my phone what direction the vehicle is pointed to avoid making a left instead of a right out of a driveway. Yes, there are solutions to these problems in theory, but in real-world application today they’re still pretty lame / inaccurate, and the solutions still seem far away (try getting a few auto mfgs to agree to a standard way of communicating a compass heading to a phone over CarPlay or Android Auto)

I've used a phone that didn't have a built in compass and one that does. The one that has an actual compass knows which direction I'm facing even without moving. The one that didn't would usually have no idea until I started moving.

They make external GPS units that plug into your car and connect to your phone wirelessly for example Garmin GLO that are supposed to improve accuracy although I haven't used one myself and thus can't vouch for it.

The built in compass in a phone is pretty inaccurate for driving because it can't compensate for the unknown shape of the body shell of the car it's in.

When turn-by-turn directions specify traveling 1 mile down a very steep grade, do they mean 1 mile along the slope, or 1 mile along a flattened map?

Only the former would match the car's odometer, of course.

Hmmm. What about the sensors on my phone? For a while now I've wanted to know my realtime speed in the underground sections of the local rail/metro network.

I suspect the most accurate measurements would be done using wideband SDR, iff I were able to acquire absolute position references for the signals I was seeing. Not likely, especially for something I might like to let others play with and/or generalize.

Everywhere I read about the subject the general consensus is that using accelerometer and gyro data from the average phone is a fool's errand. I have zero experience with the field so I wouldn't know if failure was incorrect signal processing or just had sensors.

Without wheel speed sensors, distance and speed errors quickly accumulate.

With a particle filter and enough computation, that error can be eliminated after the fact. Ie. At the time you won't know where you are, but after you get out of the metro and the particle filter reconverged you'll know where you were with more accuracy at some point in the past.

Ah. I see. Thanks very much for that insight - so that's why it's possible, but not generally interesting and/or widely pursued.

There were already workarounds in place before they switched off SA - the introduced error was consistent within a given area, so provided you had a fixed location that broadcast its coordinates, you could correct for the error. I believe there were products and possibly even standards that did all of this; would have been even easier in today's world of mobile internet. I have suspicions that this was a large reason for disabling SA - your enemy can work around it, so it's not much use, but if you get your enemy hooked on it without the work-around, you can turn SA back on in a war situation.

Also, WAAS https://www8.garmin.com/aboutGPS/waas.html

When I was a civil engineer last century gps accuracy was an issue because people wanted to use gps for surveying. They came up with a system that would use 2 receivers and a radio between them to get much higher accuracies.

https://www.e-education.psu.edu/natureofgeoinfo/book/export/...

I think the US Government can also shut it off at a moments notice.

They could, but multiple governments now publicly broadcast from similar constellations, so it wouldn't have nearly as much benefit for them to do so.

Modern dirt cheap receivers can pick up European, Chinese, Russian, etc. constellations for location just as well as the American one.

Always wondered about this, can overlapping systems be used simultaneously for higher reliability or precision?

Surprisingly the answer is most often no, however in poor signal areas like in a city or under canopy the answer is yes as you are more likely to get a signal from the remaining bits of sky view.

The other benefit is when doing PPP the convergence time is dramatically shorter with multi constellation.

When doing RTK most receivers will use only GPS, as it is generally the most accurate, but it can and will use GLONASS occasionally. I have never seen one use beidu or Galileo

Those two radio systems are still used. Just that many states have CORS sites that post correction information.

There are two frequencies (sometimes three) transmitted by the satellites. Using two frequencies allows certain atmospheric delays to be accurately estimated. Trouble is only one code is available for civilian applications. The trick with two receivers is to solve for the phase of secret signal (rather than decode it) by solving an integer least squares problem. This allows accuracy of the order of +/- 5cm

There are multiple civilian frequencies available now, and cheap receivers for 'em. I have a pair of F9P's running at present, and just received some GT-U12's for testing.

Mobile phones use dual frequencies now. Some use the Broadcom BCM47755 chip, but the most common ones are various Qualcomm Snapdragon SoCs.

https://www.broadcom.com/products/wireless/gnss-gps-socs/bcm...

https://www.euspa.europa.eu/newsroom/news/qualcomm-launches-...

https://www.gpsworld.com/qualcomm-launches-3-dual-frequency-...

What is the accuracy of GPS surveying?

I briefely looked through the pdf, and probally missed it?

I live in the Bay Area, and homeowners are concerned over a few inches.

(There's a huge need for cheap surveys. Until GPS gets it to under a inch, traditional surveys will off pipes, and landmarks, is here to stay? Or, am I wrong?)

Civil and mining engineers have been making use of centimeter-accurate GNSS configurations for years now. The equipment necessary costs a few thousand dollars, more if you need even more precision. Most major civil and mining engineering projects use self-guided earth-moving equipment, not feasible without this technology.

The problem for homeowners is that surveys aren't enough. The vast majority of land titles are not registered in precise coordinates; they're registered in terms of landmarks, benchmarks, and so forth. This is changing at a glacial pace, but for now, the tech isn't the problem.

RTK has an accuracy of around 1cm. Its widely used by surveyors (and other things like agriculture, construction machine control, etc).

As I recall, it was due to plane crash and US h̶a̶d̶ decided to make precise GPS available to public

After KAL007 was shot down by the Soviet Union in 1983 Reagan announced the fuzzy GPS signal would be publicly available. The US government didn't turn off Selective Availability until the late 90s.

That's weird though as a reason. KAL007 was so far off course that the distortion of SA wouldn't have mattered. It only distorted location by a couple hundred metres at most.

I read the GP as saying that SA GPS was originally made available as a result of the KAL007 crash, so presumably they didn’t have access to GPS at all on the flight? Then much later the SA restriction was removed, unrelated to a plane crash.

Exactly.

Though KAL007 deviated from course not because of some INS fault but just because autopilot didn't switch into INS following mode at all. Most likely crew just forgot to flip the switch, so GPS availability wouldn't have helped anyway.

Being out in the middle of the ocean with only INS supposedly keeping you on track is different than a GPS receiver that you can look at and see that you are not where you should be. Obviously the same thing would happen if no one was paying any mind to the cockpit instruments but at least a GPS receiver offers a solid reference to compare against. I really can't imagine how nerve wracking it would be trying to fly a plane without INS or GPS over an ocean. Your navigator would do their best to keep track of location but you'd probably end up way off course by the time you saw land.

Circa 1999, I was a member of a search and rescue team through the explorer scouts. We got to carry milspec GPS devices on a hike once, because the forestry service wanted accurate maps of some trails. We were under strict orders not to deviate from the trail or tamper with the devices. Very fun cloak&dagger atmosphere for what was otherwise a lovely walk in a park. Hilarious that the need for such missions was obviated a few months later

I love walking around with purpose. Like when my car didn't have a tire iron in it, so I walked home and walked back in ratty clothes with a tire iron through a couple miles of nice neighbourhood.

That's really cool. So your tracked tracks (so to speak) helped inform maps of the trails you walked?

Yes, when it first came out, it was a boon for cruising sailors such as myself who were using radio-based Loran up to that time. If I remember correctly, the civilian resolution was originally 50 meters, then lowered to 10 meters. I believe it is 1 meter today.

I've heard that just before Operation Desert Storm began in 1991 the reduced accuracy that affected civil GPS was temporarily turned off. This was a result of not being able to procure enough military grade GPS devices for army vehicles etc. If this is true it may also have had an effect on the decision to completely turn it off.

This is different but related. China has no ability to influence GPS accuracy within its borders. What they do is manipulate all of the authoritative maps available so that GPS coordinates won’t map cleanly to the digital waypoints in the map. The GPS locations are very precise, they are just off by as much as a quarter mile in varying directions depending on where in the county you are.

Can OpenStreetMap or someone make non-authoritative maps, or is this impossible without the cooperation of people on the ground who cannot operate safely within the borders of China?

At one point we spent some time reverse engineering the Chinese coordinate system, it’s actually quite fascinating. So terrible though.

But OSM actually doesn’t use that system! They use the normal coordinate system, which makes them unique across mapping services (and also a good tool to use to RE geojson away from chinas system).

It's "impossible".

Private, independent geographical surveying is illegal in China. [0] So technically you can't do it even in the local coordinate system.

[0] https://en.wikipedia.org/wiki/Restrictions_on_geographic_dat...

But I guess to OPs point, you could make a non-authoritative map based on satellite imagery, it just wouldn’t be legal to use in China.

OSM has an extensive article about mapping in China. Generally it's not allowed. Still, in the bigger OSM is quite accurate. :>

Anything that can be seen from a satellite is quite accurate, that's true, but oftentimes things like number of lanes, type or direction of the roads is unknown, footpaths in rural areas are very spotty. Basically anything that requires local human verification (addresses, business location, etc) is off limits and accuracy in those points comes from pre-ban times (or illegal activity).

> This is different but related. China has no ability to influence GPS accuracy within its borders.

FYI: And even far outside of them too

I don't think so Tim.

https://spacenews.com/pentagon-report-china-amassing-arsenal...

The current ASAT weapons can only hit targets in low earth orbit, and the GPS sats are way above that. Anything that high up that is military run also likely has capability to maneuver to avoid something shot from the surface (which will take a lot of time to get up that high even if it has enough energy).

"China already has operational ground-based missiles that can hit satellites in low-Earth orbit and “probably intends to pursue additional ASAT weapons capable of destroying satellites up to geosynchronous Earth orbit,” says the Defense Department’s annual report to Congress on China’s military capabilities."

The problem with defending a satellite is the missile really only needs to get kinda close. And yeah, relativistic speeds and distances in space are huge, but I would find it hard to believe we could defend our satellites in any meaningful way against a nation-state level threat.

At this point, destroying the positioning network/s would be mutually assured destruction. Pretty much every country relies on those networks equally for controlling their own vehicles and weaponry.

Some of those systems do. Not all.

" It is an Inertial Guidance System with an additional Star-Sighting system (this combination is known as astro-inertial guidance), which is used to correct small position and velocity errors that result from launch condition uncertainties due to errors in the submarine navigation system and errors that may have accumulated in the guidance system during the flight due to imperfect instrument calibration. GPS has been used on some test flights but is assumed not to be available for a real mission. "

https://en.wikipedia.org/wiki/Trident_(missile)

Tomahawk missiles are also fed a navigation package before launch which allows them to navigate without additional signals (I'm sure accuracy goes up if they do have GPS available). I believe it's something akin to terrain maps that it can use to navigate to it's target.

I would argue that any nation that is reliant on those public networks to be effective are going to lose within minutes of an actual conflict.

I believe it's already established that the Russians are capable of completely blocking out GPS signals.

https://www.nbcnews.com/news/vladimir-putin/russia-spoofing-...

So no, I don't think we'd be facing mutually assured destruction.

Now the impact on civilian life if some nation decided to start the space wars? Catastrophic. We'd basically block off space for the next 100 years because of deadly debris in orbit :/

And the debris created from a kinetic weapon would indiscriminately destroy other satellites at those altitudes. See https://en.wikipedia.org/wiki/Kessler_syndrome

IIRC civil GPS chips won't work above a specific altitude or when moving above some speed limit. I think the idea was to prevent people from guiding missiles using those chips.

Seems this is an ITAR restriction and only applies to chips exported from the US: https://en.wikipedia.org/wiki/Global_Positioning_System#Rest...

All 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

Really nice photos, must have been quite the trip!

Regarding 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)

Something 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)

Wow, 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.

Any info on how you setup your Cuba trip?

I simply flew there from Spain

Yeah I got into one with my Cuban gf and they didn't like my presence so I had to "hide".

They work very well via VPN. I used Google's navigation in Shanghai.

Thanks for posting it. Very interesting to read.

Recently, I discovered Street View sometimes captures car crashes:

https://goo.gl/maps/kJdgWQUU3eUMReUE8

https://ibb.co/x18fy3s

Two 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.

Well 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!

> 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

Really 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

Circumventing the obfuscation is a crime.

In China? Is it a violation of the data source license?

See the explanation on Wikipedia: https://en.wikipedia.org/wiki/Restrictions_on_geographic_dat...

Indeed, there's a Half As Interesting video talking about this: https://www.youtube.com/watch?v=L9Di-UVC-_4

I'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?

> 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.

I 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.

> 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!)

Neither. 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

>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....

The BBC article in the submission mentions this restriction and the Kyl-Bingaman Amendment.

Have you checked out South Korea?

South 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.

It's a similar law to what's discussed here. The justification is protection from NK.

Could it be a licensing issue?

Naver Maps has really good street view and very accurate maps in SK.

https://map.naver.com/

https://www.google.com/amp/s/www.wsj.com/amp/articles/google...

My 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.

Some more info: https://ogleearth.com/2012/07/constraining-online-maps-the-c...

>Why is Google’s Korean map behaving this way? In short, because of Korea’s Spatial Data Industry Promotion Act from 2009, specifically Article 7, which states that:

>Spatial data business operators may produce and distribute any processed spatial data. In such cases, processed spatial data shall not include any spatial data on any military base provided for in subparagraph 1 of Article 2 of the Protection of Military Bases and Installations Act nor on any military installation provided for in subparagraph 2 of the said Article.

>And considering the existence of the most heavily militarized border on the planet between North Korea and South Korea, this means a substantial part of South Korea is riddled with military installations.

>By limiting the maximum resolution of its Korean imagery on maps.google.co.kr, Google appears to have satisfied Korean regulators that it is obeying the relevant Korean laws. Thus, Google avoids having to blur or otherwise censor the satellite imagery base layer for Korea — something which it has successfully managed to avoid in China, India and elsewhere.

Write up about Apples courser application

https://ogleearth.com/2012/07/apple-censors-ipad-maps-app-ov...

Can 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.

I can't wait for the BBC to publish an article about the inaccuracies in China ...

> 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-warni...

https://www.google.co.uk/maps/@42.4300052,130.6278764,3096m/... China's roads appearing to cross into Russia.

https://goo.gl/maps/oDwCuGhxxZVSj7nJ6 Hong Kong/China border bridges

Openstreetmaps works correctly.

> 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?

> 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.

When I last went in late 2018, it was not corrected for on the satellite maps. Google maps was still usable for walking directions, however.

Isnt it that all google services are not available in china, so it might not be possible to use google maps inside china.

When it still was available they had a license, but only when using Google Maps in China.

My 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.

I learned earlier today that the little google street view man nopes the fuck out of Kabal.

Reply on news.ycombinator.com