7 ms·

You can see how much Google skews their map for China, such as by looking at Beijing: http://labs.strava.com/heatmap/#15/116.46747/39.94133/gray/both http://lab

You can see how much Google skews their map for China, such as by looking at Beijing: http://labs.strava.com/heatmap/#15/116.46747/39.94133/gray/both http://labs.strava.com/heatmap/#15/116.46747/39.94133/gray/b... Vs a similar map for Tokyo: http://labs.strava.com/heatmap/#15/-220.36217/35.60747/gray/both http://labs.strava.com/heatmap/#15/-220.36217/35.60747/gray/...

edraferi 12y ago
I don't get it. What am I looking for?
- KnightHawk3 12y ago
  The paths ridden do not line up with the actual roads. I am not sure what the OP is actually trying to tell us about that though.
  - Holbein 12y ago
    There seems to be a chinese decree that all maps must be skewed so that in the case of being attacked, an attacker can presumably not find its way around the chinese capital. Bike maps are likely created directly from GPS paths, which are unskewed. When you look at Bejing, you can easily see that difference.
    - 1stop 12y ago
      Exactly, similar to that thing in the US before they opened up civilian GPS accuracy...
      - alexkus 12y ago
        Not quite, the difference between the two situations is the difference between accuracy and precision. E.g. http://academics.wellesley.edu/Chemistry/Chem105manual/Appendices/AccuracyPrecision.gif http://academics.wellesley.edu/Chemistry/Chem105manual/Appen... The Chinese Street maps are very precise but consitently inaccurate (the skew). The GPS tracks shown are relatively precise and accurate. The change to the GPS signals (by not encrypting as much of the timestamp data) improved precision.
jamesaguilar 12y ago
It is unclear to me whether Google is skewing or Strava. I would tend to assume the latter, but I'm a little biased in that regard.
- ivank 12y ago
  Zoom into Beijing in Google Maps; switch between the default and satellite view and you'll see that they don't line up. https://productforums.google.com/forum/#!msg/maps/ambcCIPTQiI/8PuAsJfyEXAJ https://productforums.google.com/forum/#!msg/maps/ambcCIPTQi... says that the satellite images are correct and that the street maps are misaligned.
- colordrops 12y ago
  I've built map applications while based in Beijing. Google is definitely skewed here, by decree of the Chinese government. The interesting thing is that the skew is different for various regions in China, but it hasn't changed for years. If you correct for the offset in Beijing, everything will be fine as it is the same across the whole city. You can create a map of offsets for the major cities and be done with it. They claim that the offset is for security purposes but this simple fix shows that the excuse is bullshit. In reality the Chinese put all kinds of barriers to entry for foreign companies to make it difficult to penetrate the market. Another example is that you have to dual home your servers to both china unicom and china Telecom, as the traffic between the two networks is degraded on purpose. You thus have to purchase a special DNS service that differentiates between requests on the two networks. In the same vein, the purpose of the great firewall is more economic than political, being a highly successful form of protectionism.
  - PeterisP 12y ago
    Why don't non-china mapping companies have a table of these offsets and simply apply them everywhere (well, maybe except chinese IP adresses) ? It seems a tiny amount of work compared to, say, gathering the actual street data itself; and it would be an useful thing to make this data available to the public like openstreetmap data.
randomstring 12y ago
I think you're seeing a couple different effects here. 1. The data is reported from a many varieties of GPS devices and phones. So the data is noisy. Some singles tracks will be very noisy, to the point of being fiction. 2. Not all of these tracks are on the road. If you click between bike/run/both you'll see the bike rides are more correlated with roads and the runs seem to have more "off roading." 3. some of those paths are sidewalks and pedestrian bridges and underpasses.
- 1stop 12y ago
  Have a look in GuangZhou it is definitely the China GPS skew crap. The major routes are offset north and west of the actual roads: i.e. People are not really running/riding through lakes and rivers ;)
- deleted 12y ago
  [deleted]
NAFV_P 12y ago
It seems the gps data lies SWW of the map view.

edraferi 12y ago

I don't get it. What am I looking for?

KnightHawk3 12y ago
The paths ridden do not line up with the actual roads. I am not sure what the OP is actually trying to tell us about that though.
- Holbein 12y ago
  There seems to be a chinese decree that all maps must be skewed so that in the case of being attacked, an attacker can presumably not find its way around the chinese capital. Bike maps are likely created directly from GPS paths, which are unskewed. When you look at Bejing, you can easily see that difference.
  - 1stop 12y ago
    Exactly, similar to that thing in the US before they opened up civilian GPS accuracy...
    - alexkus 12y ago
      Not quite, the difference between the two situations is the difference between accuracy and precision. E.g. http://academics.wellesley.edu/Chemistry/Chem105manual/Appendices/AccuracyPrecision.gif http://academics.wellesley.edu/Chemistry/Chem105manual/Appen... The Chinese Street maps are very precise but consitently inaccurate (the skew). The GPS tracks shown are relatively precise and accurate. The change to the GPS signals (by not encrypting as much of the timestamp data) improved precision.

jamesaguilar 12y ago

It is unclear to me whether Google is skewing or Strava. I would tend to assume the latter, but I'm a little biased in that regard.

ivank 12y ago
Zoom into Beijing in Google Maps; switch between the default and satellite view and you'll see that they don't line up. https://productforums.google.com/forum/#!msg/maps/ambcCIPTQiI/8PuAsJfyEXAJ https://productforums.google.com/forum/#!msg/maps/ambcCIPTQi... says that the satellite images are correct and that the street maps are misaligned.
colordrops 12y ago
I've built map applications while based in Beijing. Google is definitely skewed here, by decree of the Chinese government. The interesting thing is that the skew is different for various regions in China, but it hasn't changed for years. If you correct for the offset in Beijing, everything will be fine as it is the same across the whole city. You can create a map of offsets for the major cities and be done with it. They claim that the offset is for security purposes but this simple fix shows that the excuse is bullshit. In reality the Chinese put all kinds of barriers to entry for foreign companies to make it difficult to penetrate the market. Another example is that you have to dual home your servers to both china unicom and china Telecom, as the traffic between the two networks is degraded on purpose. You thus have to purchase a special DNS service that differentiates between requests on the two networks. In the same vein, the purpose of the great firewall is more economic than political, being a highly successful form of protectionism.
- PeterisP 12y ago
  Why don't non-china mapping companies have a table of these offsets and simply apply them everywhere (well, maybe except chinese IP adresses) ? It seems a tiny amount of work compared to, say, gathering the actual street data itself; and it would be an useful thing to make this data available to the public like openstreetmap data.

randomstring 12y ago

I think you're seeing a couple different effects here. 1. The data is reported from a many varieties of GPS devices and phones. So the data is noisy. Some singles tracks will be very noisy, to the point of being fiction. 2. Not all of these tracks are on the road. If you click between bike/run/both you'll see the bike rides are more correlated with roads and the runs seem to have more "off roading." 3. some of those paths are sidewalks and pedestrian bridges and underpasses.

1stop 12y ago
Have a look in GuangZhou it is definitely the China GPS skew crap. The major routes are offset north and west of the actual roads: i.e. People are not really running/riding through lakes and rivers ;)
deleted 12y ago
[deleted]

NAFV_P 12y ago

It seems the gps data lies SWW of the map view.