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Chinese satellite data randomly manipulated?

My Nike+ GPS watch (with TomTom co-branding), a cool gadget
During my last trip to California I bought a Nike+ watch to record my runs. The watch (powered by TomTom) uses satellite navigation to calculate your position, so you can get all kinds of statistics about your runs. A cool gadget that worked flawlessly in the US, Germany and Luxembourg over the past 2 weeks. But not in China: when I did an outside run today and looked at the map of my run afterward I realized that the data are incorrect. This is the map of my run:

Map of my run is incorrect due to manipulation of satellite data in China...

My start and end position are the same, but on the map they appear at different locations. That’s already an indication that something is not right. Next to that both the start and end position are in the wrong location, both are about 200-300 meters off the real place. During the run you can really see that the satellite data is manipulated, because I ran 4 loops of each about 900 meters (exactly the same loop 4 times in a row). The first one measured 800 meters, the second one 920, the third 850 and the fourth 880, too much of an error margin to be reasonable. When you look on the map you can see why: none of the 4 loops is in the same position! While running, the satellite changes the data it sends to my watch, meaning that you never know exactly where you are.

I re-checked my runs in Europe and the US and there is no error whatsoever. So it is China specific. This means the watch is not very useful here, at least not for precise measurements. I read before about GPS data from non-Chinese devices (=data from non-Chinese satellites) being slightly incorrect, but I did not realize how big the error is until I saw it myself. And worse, the error seems to change randomly over time.

Luckily I mainly run on my home treadmill when in Shanghai: air pollution is normally too bad to run outside, but today it was raining so I made an exception to run in the open air. So when I use my watch it’s normally outside China where it works well. But it still sucks that Big Brother is messing with satellite data. At least I now know it, so I won’t rely on my watch to tell me exactly where I am.

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  1. My Garmin Forerunner GPS running watch
    seems to work fine here in China but I
    don’t check it very much any more. Based
    on your input, I’ll check again.

  2. Hi Marc, you’ve involved in a couple startups in China (Spil, Tudou, and UnitedStyles), what are the best ways to hire people for early-stage startups (from your experience)? thanks!

  3. Hey Marc!

    I’m using Runkeeper appz on my G5 Android phone from US.

    One thing is true about the GPS route on Gmap in China: there’s an offset on Gmap in map mode compared to the real route. The Chinese government censors GPS route on Gmap in map mode and I’ve never known why. Even my Chinese runner friends don’t know. However, have you try to switch to satellite mode on Gmap? You’ll notice that surprisingly, there’s no offset when you use the satellite mode instead of the map mode. I’ve no explanations about that…

    However your 2nd issue -the loops are drifted whereas you ran on the exaclty same route- is weird. I’ve never met this issue in China. Usually, my GPS will record the route correctly even if I do several identical loops and I can see them on Gmap in satellite mode. Only if my GPS has a poor reception, which happens in some part of Shanghai, the route can be twisted.

    Therefore, I don’t know what happened with your Nike+ GPS watch…

  4. Pengfei, best way to hire people for start-ups is through your own network. Find one or two key people and ask they to look in their network for others. Job sites can also be useful, but you’ll get swamped in applications, and half the people won’t show up at job interviews. But you still may be able to find some really good people in this way, it just takes a lot more effort.

  5. As Geoffrey says, there are two issues at play:

    1. In China, GPS gives correct readings (subject to caveats below). What’s shifted is the *maps*. The shift varies depending on the city and map provider. For Shanghai, and Google Maps, everything is about -0.0016 shifted in latitude and 0.0044 shifted in longitude. This has been the case for several years, and noone seems to be certain why it was done like this originally. The satellite maps used in Google Maps and Google Earth are not shifted (making it pretty easy to calculate the shifts if needed!)

    2. GPS *reception* in China can be lousy, due to: lots of skyscrapers and trees blocking the satellite signals, lots of electrical interference. Also the Nike watch uses GPS only, not “assisted GPS” like on an iPhone, which additionally uses cell triangulation and wifi networks to lock onto a signal more quickly. Therefore, my guess would be that your watch was struggling to lock onto a signal. If you go for a longer run in more open terrain, I think you’ll find the “constant” shift indicated above.

  6. I rechecked my Garmin watch = ran a few laps on the track at Shanghai American School and the distance was right on.

    When I exported the track to Google
    Earth it was right on the track of
    the Sat pict. I’ve seen offsets on
    western GPS systems in the car but
    not on Shinco chinese brand, the only
    one I could find at the time with
    Pin ying = latinized Chinese street

  7. Hey Marc,

    Interesting article.

    When I was doing research for TomTom in China in 2006, I found that the Chinese personal navigation market was using a special chip to decode GPS coordinates into Chinese map coordinates.

    If not using this chip to convert the coordinates, this could result in an error up to 2,000meter (compared to GPS error margin of 10meter).

    That time the source came from the General Manager of NAV2, a JV of Navteq and Si Wei (governmental mapping institution).

    So as far as I heard all Chinese consumer navigation systems are equipped with this chip….

    This might explain the huge error in location estimation.

  8. Interesting sharing.

    I’ve lived in Shanghai for 2 years with my iPhone purchased overseas. I found if I use the Maps app (google maps) coming with iPhone, my location points perfectly correct all the time.

    However, if I use the google Latitude app, my location will shift 200-300 meters.

    Recently, I purchased Nokia Lumia 800, and unfortunately, both Nokia Maps and Nokia Drive shift my location. This is really bothering.