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I am trying to use Google Maps in China. I know that Google is blocked, which is why I downloaded the map of Beijing offline. However, when I open the app my phone attempts to find GPS satellites but finds none. I know location works because my location works fine when I am on WiFi. Is this a China blocking GPS thing or something else?

I am using a Verizon HTC One (M8) with Android 5.0.1 and HTC Sense.

Note: This question has also been cross-posted to Android.SE.

Update 1:

All my testing for this question was done on the 7th floor of a downtown office building. Yesterday after waiting a while, I was able to recieve GPS signal (using both Google Maps and GPS Status) while on the 17th floor of a suburban apartment building. I was then also able to recieve signal in another part of downtown that lacked many tall buildings. When I get back to the office tomorrow I will be able to judge if it was just taking a mega-long time to get the satellite data as @Vince suggested, or if it is the urban canyon as @Loren suggested. Thank you all for the help and explanations!

Update 2:

After some testing, it seems that this does simply come down to an urban canyon problem. The GPS does not find any satellites at my desk in the office, however, if I bring it next to a window it finds 2 satellites (not enough for a location, but enough to answer this question). When I take the phone outside the building I am able to get location in some areas. Thank you all again for the help and the wealth of new knowledge.

Note: all testing was done with data and WiFi services turned off.

Based on a comment, I have asked a question in GIS.SE asking about the urban canyon and how it compares to Beijing versus NYC.

  • Heh, there's apps that will show you what satillites your phone is picking up, which may be useful here. – Journeyman Geek Mar 27 '15 at 0:15
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    heh, that's what I use, so no – Journeyman Geek Mar 27 '15 at 0:47
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    I have cross-posted on Android Enthusiasts – Matthew Herbst Mar 27 '15 at 7:42
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    In general, you should always keep your original question edited to contain the latest updates. Each time you edit your original question, you will bump it to the top of the homepage, which is likely to get it more attention. – unforgettableid Mar 27 '15 at 20:40
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    You also can post in the gis.stackexchange.com chat room, both to try to get answers or (if you post then log off immediately) to draw attention here. There are expert geographers there. If you cross-post there, you could get a reply even after you leave; please edit your original question to say that you have cross-posted to there. – unforgettableid Mar 27 '15 at 20:41
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Long ago I took a fairly simple GPS (coordinates only, this was before the idea of a GPS with a map existed) to China--and found it couldn't cope with all the tall buildings. In a large park it would work. Once I managed to get a fix with it sitting on a windowsill high up in a building but at street level with buildings around I never got enough satellites for a fix.

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    Not sure this makes any sense - I can use GPS in NYC just fine and Beijing has almost no "tall" building relatively speaking. Further, the buildings in Beijing are very well spread out, and my Chinese friends with Chinese phones get GPS just fine. – Matthew Herbst Mar 27 '15 at 6:57
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    It actually makes a lot of sense. The fact that your device knows its position in New York does not mean it uses the GPS for that (using 3G/4G provides a better precision) In fact GPS signals are coming from satellites so any obstacle, buildings or even trees, weaken or reflect the signals. – Vince Mar 27 '15 at 10:33
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    @MatthewHerbst: Your phone supports "assisted GPS", which helps in downtown areas. Loren's GPS device didn't. – unforgettableid Mar 27 '15 at 21:17
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    @MatthewHerbst: It makes perfect sense; multipath is a huge problem in the urban canyon. – Lightness Races with Monica Mar 28 '15 at 17:30
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    If you have a street level precision, that must be GPS. 3G/4G geolocation can only give you rough location, usually only to the suburb level precision. If you've got higher precision than that without GPS, it's likely Wi-Fi positioning, but that requires a Wi-Fi database, and given China's law and their poor relationship with Google, it's unlikely they would ever be allowed to build such database. – Lie Ryan Mar 30 '15 at 0:04
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This may be due to the long Time To First Fix. Indeed, I recently learned that recent smartphones use mechanisms called "Assisted GPS" in order to get a location based on GPS reception. The idea is that if you use your GPS in an area you haven't been before, the GPS would take some time to find and interpret the signal, mostly because of the slow download speed from a satellite (the source of the Wikipedia article mentions 12 minutes to get an entire navigation message, to locate the device).

To solve this issue and make it more usable for today's impatient phone users, phones use the data network (WiFi/mobile) in order to approximate the location of the phone and download the almanac of GPS satellites positions. With this information, the GPS signal is more likely to be found faster with a better precision. As @AdamDavis details in his comment, the technologies providing this solution may not be the same in every country, or even be available.

So your problem might just be that you are not waiting long enough for the phone to locate itself. I would suggest to try to use the GPS feature while connected to WiFi, or just be patient.

Note that anyway, China cannot block the GPS signal. As some commenters say, it might definitely be possible to use jammers to alter (not block) the signal, but I suppose there would be a need for a lot of jammers to cover the whole country. And I am not sure it is possible to jam these signals without altering, at least partially, other telecommunication signals. The GPS signals are sent by US Air Force satellites, it might be possible that they can control finely in time what satellites send what signals and with what precision, but again I doubt of that (the communication with the satellite might be too slow to offer such fine configuration, if it is even performed). As some commented, it is hard to even configure that for a specific area on Earth as the satellites are not geostationary (I.e. a satellite will pass over multiple continents within a day). I am no expert in that field, though.

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    In the US, Assisted GPS is provided by the phone carriers through the towers and the phone's control channel. This service is not necessarily provided by carrier towers outside the US. However, once connected to a wifi network the phone can get the assisted gps information that way. Some phones don't have a full GPS chipset, and so they cannot attain a GPS fix without carrier support, relying entirely on assisted GPS. – Adam Davis Mar 26 '15 at 11:57
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    It's actually the US Air Force that is in charge of the system, not the Army. – Nattgew Mar 26 '15 at 14:41
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    It is certainly possible for China to jam GPS networks. Of course, this would jam all GPS, so it's not exactly in their interest to do so. – gerrit Mar 26 '15 at 15:20
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    The reason why assisted GPS helps: All satellites send their signals at the same frequency, but because they are moving around in space at high speeds, your GPS receives their signals at slightly different frequencies. When you turn on GPS, it has to scan the whole frequency band to find the satellites. With assisted GPS, your phone carrier gives you a rough estimate of where you are and what time it is, say within half a mile and a second. With that information, your GPS can figure out where the satellites are and how they are moving, and calculate at what ... – gnasher729 Mar 26 '15 at 17:48
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    ... frequency their signals would be received. So your GPS goes directly to the right frequencies instead of having to scan the whole band. There is an additional long delay if a brand new GPS is turned on for the very first time, because it has no idea where the satellites are supposed to be and needs to download that information from the satellites, which is a very slow process. – gnasher729 Mar 26 '15 at 17:51
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Vince covers the likely explanation, but unfortunately there are several more sinister possibilities as well. Long story short, China's legislation on GPS is both really vague and in part secret: by some readings of the law all use of GPS devices is technically prohibited, and not a few cameras and other GPS-enabled devices go so far as to disable GPS entirely if they realize they're within China's boundaries.

Now to be clear here, disabling GPS like this is entirely up to the manufacturer, China itself does not block or attempt to block GPS as far as I know. And with something on the order of 1.2 billion phones in use in China, the vast majority of them with GPS enabled and heavily used by locals, any notional prohibition on GPS is pretty much a dead letter — although it'll be interesting to see if China's version of GPS, Beidou, is made mandatory once it launches.

Even if you do get the GPS working, you may find that your favorite Western mapping service doesn't show satellite imagery in the right location, with imagery instead "randomly" shifted. Chinese services like Baidu and Sohu, on the other hand, will work fine.

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    How does the camera know it's in China without using GPS? :-) – David Richerby Mar 26 '15 at 17:39
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    @DavidRicherby I think it measures the pollution in the air. Alternatively, the air is so thick with pollution that the GPS signals are blocked. – emory Mar 26 '15 at 20:14
  • Hmm. I wonder if this could be related. What @Vince describes makes the most sense, however, when I try to use another app that I have, "GPS Status" it tells me that it has successfully downloaded "GPS Assistance data" yet it still cannot seem to get a fix on my GPS location. It puts a nice notification in the toolbar that currently reads "SAT 0/12 | SIG 0/inf | TTF 240s". For the record, I am using a Verizon HTC One M8 and currently have a China Unicom SIM card in it. – Matthew Herbst Mar 27 '15 at 0:05
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    @Matthew indeed this answer would make more sense if GPSStatus says that. For me the app usually takes 10-30 seconds to go from 0/0 to 0/12 (or some other number around 10) and then the same amount of time to get the left number around 10. The rest I never really understood or looked up. – Vince Mar 27 '15 at 4:37
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    This answer sounds unlikely. Chinese Android phones feature GPS support, and as a possibly-related issue, I've found that some of them fail to work entirely in the US. Thus I suspect the "not working without carrier/tower assistance" explanation is much more likely. – R.. Mar 28 '15 at 0:23
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Many good answers here already. But I have been to China before, and used GPS with a very good precision, and with Google Maps. Also, dealing with the coordinates and mobile device GPS is part of my profession, so let me pitch in.

GPS satellites are nothing more than a satellite network that spreads a signal of a timestamp that mobile phones or any GPS chip can catch, and then figure out the longitude, latitude, and the altitude. It works anywhere in the Earth surface unless it's jammed. In addition to GPS signals, mobile phones can use the location data provided by the mobile carrier (GSM, 2G, 3G and LTE) to assist in this.

I do not have any references, but China does not block GPS signals. It does however block Google, which can prevent your phone's Google Maps app from showing your location on a map. Accessing Google services in China is somewhat troublesome. Gmail, Google search, and many other services are blocked. Google Maps, however, worked very well in Beijing. China's firewall is based on IP addresses and host names, so it's possible that I was lucky to access it somehow.

The reason why you can find your location when you are connected to a WiFi network is because your phone can use triangulation to determine your location. It just uses nearby wifi network names and query Google/Apple services to get the location, which would have been recorded before through other people. You do not need to connect to any network. Your phone can get the signal strength (measured in dB), and figure out the location.

What you really need is a good offline map, because Google services are inaccessible. I have had a lot of success with Open Street Map (iPhone/Android: "City Maps to Go" app can download them for you, and provide GPS pin pointing feature on the maps). Works very well in China.

For better GPS connectivity, try to get your phone outdoors and keep a direct line to the sky. There is a lot of fog/smoke condition in China, specially Beijing. It's just factory smoke and nothing with iron particles (which can counter act signals). Keep your Wifi turned on. If you are nearby any public wifi hotspot, there is a very good chance of finding your location quickly.

  • OSMAnd is also a good offline map app for Android (by the team behind OpenStreetMap). I didn't try it in China but if what you say is true, there should not be any issue. – Vince Mar 28 '15 at 23:58
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    You can also access Chinese Google Maps at ditu.google.cn. – lambshaanxy Mar 29 '15 at 11:18
  • Openstreetmap may work well, but is it legal? – gerrit Apr 25 at 8:28
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Download Baidu Map. Or Autonavi. They are both free softwares, and has English version for foreign tourists. I am Chinese.

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    I looked at Baidu Map. I refuse to give it all the permissions it wants and absolutely doesn't need. I'll take a look at the other one, thanks. – Matthew Herbst Mar 27 '15 at 3:55
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    @MatthewHerbst: On certain Android phones, you can use App Ops to take away permissions from Baidu Map. It might (or might not) be necessary to "root" your phone before you can use App Ops. If you want more information, try a Web search or post a question on Android.SE. – unforgettableid Mar 27 '15 at 21:13
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It might because China blocks the (Google) SUPL server that is needed for AGPS. A recent story says that Xiomi devices (even those with a global ROM) use the China Telecom SUPL server.

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