Problem with China maps

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  • #4044
    • Topics: 19
    • Replies: 38

    I encountered this with MotionX, and now with PocketEarth.
    Why are GPS apps not accurate when it comes to China maps? I used OSM, Bing, Google, all same consistent errors.
    Either I be in Shanghai, or in some secluded cities midwest, or coastal towns, Apps like PocketEarth would give me a coordinate that is about 200 meters by 30* NW off. It is consistent which suggests that it is not a random error. Either I be in Shanghai or Xiamen, the coordinate always shows the same discrepancy.

    MotionX told me that China had put a restriction on map gathering, thus maps are inaccurate.
    Yet GPS installed on some popular automobiles functions properly, showing the correct coordinates.

    I am not sure if this is a permanent map-skewing-effort by China but, In this light, is it possible to add a feature on PocketEarth that will offset the coordinate so it will match the predownloaded map?

    • Topics: 32
    • Replies: 799

    Thanks for letting us know about this issue! After doing some research, it appears that the GPS and maps are not aligned in *some* towns in China due to intentional skewing. GPS devices made in China for domestic use there apparently “un-skew” the GPS location fixes thus placing it correctly on the map.

    I will discuss this issue with my team and try to work-around it with an offset setting or in some other way.
    • Topics: 19
    • Replies: 38

    Additional Info:
    I tried to overlay my saved routes with Google Satellite and Bing Satellite maps; the coordinates matched perfectly.

    But when I tried to overlay the routes with streetmaps from OSM, Bing, Google, it does not match. The discrepancy with Google streetmap is 580 meters 128* Bearing. I could not measure with OSM or Bing as I these two do not have maps on the routes I saved.

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