Google Maps in China

[Menion]

Hi to all,
  so I thought about adding Google maps for China. It's simple, they're there or can be added from http://ditu.google.cn/.

anyway, basic google maps have one problem. They're shifted by unknown value. Simple try. Looks in Locus with OSM maps on any place in china, then switch to google hybrid. Everything nice right? Fine, then switch to google basic ... still nice?

So, I want to add some fix to this. Few guys from China already asked me for this and now looks we'll have also China translation ...

so possibilities are two as I know

1) someone find any algorithm that do this shift!

2) if this shift is changing slowly, someone create for me some raster with identical points and shift value at these points and I'll do some interpolation in application from these values.

so, any idea?

[liang3404814]

For the trouble with with Google Maps in China, I Googled and found that although there are people figuring out ways to analyze google's Javascript tricks(to present the right picture at the right place), recently Google has changed the interface so the old ways are rendered useless.

The new method gets the image from

http://mt1.google.cn/vt/lyrs=s@58&gl=cn ... =14&s=Gali

and

http://khm1.google.com/kh/v=58&x=13381& ... =14&s=Gali


to see the shift in the coordinates in the centre of picture.




(Origin: http://wap.anttna.com/index-wap2.php?p=641 I'm not so confident if I could translate the site well...)

[rijackson741]

Anyone intending to go to China with Locus should be aware of this:

http://news.xinhuanet.com/english2010/c ... 302696.htm

As I read it, if you even have China maps on your phone you are violating the law. If you create so much as one POI you are breaking the law.

Talk about draconian!

(and if you are dumb enough to stand outside a military base entering POI information, see you in 20 years   )

[wldbest]

i checked hybrid map and it seems works fine

but i had made POIs based on shifted google roadmap.
it still causes big problems.

could you please implement manual calibration?
i think google chages algorithm regurally
so manual calibration is good enough.

entering numbers east/north or
manually move map to current gps location..

i really need this fearure.
my pois are useless now...
 i spent much time finding some pois...

[rijackson741]

Google gets the mapping data from China. The Chinese government supplies that data with offsets that vary across the country. The offset information is not available to anyone other than a few certified Chinese mapping companies, and certainly not to any foreign entity. All maps based on that data, which includes, Google, Microsoft, etc, show identical offsets. The only maps that are not affected are satellite images from Google (and maybe also from ArcGIS; I haven't checked), and OSM. OSM is correct because it's not under the control of the Chinese government, but that means even having it on your phone in China is illegal. I personally couldn't care less about that (just don't stand next to a police officer and play with the mapping on your phone!), but OSM maps have so little information they are essentially useless outside the major cities. The one thing I can think of that is a viable, if not ideal, solution, is to allow maps to be offset by the user. That offset could be figured out using the crude OSM maps or satellite images before even going to the specific location. Since it varies by location, it would be almost essential that the offsets could be stored, and recalled later. Allowing for such user defined offsets would also fix a couple of issues unrelated to China: //http://forum.asamm.cz/viewtopic.php?f=10&t=659&p=3968&hilit=beijing#p3968

[rijackson741]

The one thing I can think of that is a viable, if not ideal, solution, is to allow maps to be offset by the user. That offset could be figured out using the crude OSM maps or satellite images before even going to the specific location. Since it varies by location, it would be almost essential that the offsets could be stored, and recalled later. Allowing for such user defined offsets would also fix a couple of issues unrelated to China: //http://forum.asamm.cz/viewtopic.php?f=10&t=659&p=3968&hilit=beijing#p3968

I'm off to China very soon (maybe as early as Saturday). Any thoughts on the idea of user offsets for maps? I realize this is a far from ideal solution, but I can't think of any other one.

[Menion]

from my side no. I'm sorry but I have no reason to support some offset for maps. Google maps aren't supported by locus and no other map need this

[rijackson741]

no other map need this

Also OVI, Bing, and Yahoo maps, and any off-line map created from these sources. Although, since they are not supported either I guess the answer is still no.

As far as I can tell, outside Beijing and parts of Shanghai (where OSM maps are good) any map with enough detail to be useful to someone walking has the offsets, because the data was supplied by the Chinese government. So, sadly, outside a couple of locations, Locus is not very useful in China. I think you are in good company though, because I don't think there are any other mapping apps that are any better in this regard.

[Menion]

OVI Bing and Yahoo maps also need this offset?? Anyway, non of them are officially supported as you surely know ... ok, I'll try to look at it soon ... anyway till sunday it surely not will be completed

[rijackson741]

OVI Bing and Yahoo maps also need this offset??

Yes. The offsets for these maps are in fact all the same (at least, based on my limited testing, they are). To be fair, the Bing and Yahoo maps do not have enough detail to be useful anyway, even if they did not have the offsets, but the OVI and Google maps are very good.

Because I travel to China quite a lot I did some research into the problem. All mapping data supplied by the Chinese government, which means all official mapping data from China, has these offsets. It seems kind of pointless to me, since any country or entity with enough power to even contemplate attacking China surely has accurate maps anyway, but things are not always logical!

Anyway, non of them are officially supported as you surely know ...

Yes, I realize that. I do not think there are any officially supported maps with much detail outside Beijing and Shanghai.

ok, I'll try to look at it soon ... anyway till sunday it surely not will be completed

Thanks. That is greatly appreciated.  :mrgreen:

Don't knock yourself out getting it done though. I realize that Sunday is a too short a time to get something like this done. I didn't know until yesterday morning that I was even going though; it's a very short notice trip. When I found out I was going it made me think of it again, but when I asked about it I didn't expect a solution by the time I left.

Also, when I'm there my chances of being able to download a new version are slim. I do not allow data roaming, and free WiFi hotspots are almost non-existent. There is going to be a next time though, and of course other users will also benefit from this.

Thanks again  

[Menion]

hi,
  are you in China? Check new version from market (currently uploading). Go to functions and scroll down .. there's new "Map offset" tool ...

[rijackson741]

hi,  are you in China?

No. My trip got delayed. I have now been told that I have to be there soon, but I don't know exactly when. Maybe before the end of the week, maybe not until the middle of December. PITA :roll:

Check new version from market (currently uploading). Go to functions and scroll down .. there's new "Map offset" tool ...

Thanks Excellent.    I'll check how it works.

[rijackson741]

This seems to solve the problem. I can now get my maps to line up properly with each other. I'll check it works with the GPS when I'm in China (although I can't see why it wouldn't!). Since the offsets vary from one place to another it would be nice if we could store multiple sets, with a name for each. That's not really necessary though, because I can store them in another file and copy and paste them into Locus

Working out the correct offsets is rather painful, so for anyone that wants them:
In Beijing: Forbidden City (in the center), 533m and 159m; Friendship Hotel (NW from the center, by the third ringroad), 518m and 139m; Summer Palace (NW from the center, by the fifth ringroad), 508m and 132m
Chengdu center: 250m and -265m.
I'll add other locations when I figure them out.

Thanks very much for this. It is going to make it so much easier when I'm in China!  :mrgreen:

[EGE]

This resolved the problem for me too.

For Shanghai I used:
-420
230

Thank you Menion for the good work!

[jeanwills]

thanks for all of these!