Map a trip to China

12/27/2016

We do not presume to offer any advice on actually traveling to China. We can however assist with some of the preparation, specifically we can help you plot your trip itinerary on the map.

It's worth noticing that as civilized and connected as it is nowadays, China remains a totalitarian regime. The laws are restrictive and the government actions are pernicious. Even a simple act of mapping one's trip is political and it does not escape bureaucratic regulations that inconvenience people in the name of fighting real and phantom enemies.

The difficulty of mapping a trip to China stems from the government decree that establishes a unique coordinate system, called GCJ-02. Differently from other major coordinate systems, GCJ-02 is not designed to improve accuracy. On the contrary, its purpose is to obfuscate and distort in the misguided attempt to protect the so called state secrets.

Furkot displays maps using Google Maps API which - in China - employs GCJ-02 for the road and terrain projections but not for the satellite imagery. The latter employs WGS-84 system widely used around the world. The use of 2 different and incompatible systems is easily noticeable if you try to overlay roads network over the satellite imagery.

China GPS shift

Border crossing

The shift between coordinate systems occurs at the Chinese border introducing a gap between roads on each side of the border crossings. If your trip to China involves crossing a land border, Furkot will not be able to calculate a route between points on the opposite sides of the border and will display a No route available... warning. You can however work around this issue.

Border crossing

After independently verifying the border crossing locations add 2 stops: one at the road end on each side of the border. In the Plan drawer select the route segment between the newly added stops and change its Routing setting to travel off road. The Routing setting is an advanced feature: use the advanced use button under the Plan drawer filter to enable it.

GPX files

Importing and exporting GPX files poses significant problems because the specification of the GPX format mandates use of the WGS-84 coordinate system and most GPS devices available in Western countries follow the specification.

If you intend to export your planned trip in the GPX format to use with a navigation app or a GPS device, you need to make sure your trip in WGS-84 coordinate system. You can take advantage of alternate routes as they are always calculated in that coordinate system. Plotting the routes as off road tracks tracing roads displayed by the satellite imagery works as well. You can also import GPX waypoints, routes and tracks to add to your trip as if they are already in the correct coordinate system.

Make sure all stops are placed in correct locations either by editing their coordinates directly (Furkot takes and displays stop coordinates in the WGS-84 system) or dragging the stop across the satellite imagery.

If you want waypoints, routes or tracks from an imported GPX file to display correctly on the map, you need to convert their coordinates to GCJ-20. Move every added waypoint from an imported file to the correct location using the road map projection. Change the Routing setting for every added route or track to follow roads or press the Regular button and click the proposed regular route to use it in your trip.

Planning a trip to China is hard enough without dealing with the vagaries of Chinese maps. We would like to improve that aspect of Furkot and we are working on an automatic conversion between GCJ-20 and WGS-84. For now please be aware of the issues and, when needed, employ the suggested workarounds.