Problem with China maps

[ragnakore]

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?

[GeoMagik]

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.

[ragnakore]

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.

[Auteur]

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