Input
Results
| Operation | Result | ΔObfs/m | ΔRoundtrip/m |
|---|---|---|---|
| WGS → GCJ | (38.88551584, -76.98462705) 38°53′7.857″ N, 76°59′4.6574″ W | 3.359716814478211e+3 | 1.755640930518561e+1 |
| WGS → BD | (38.89174261, -76.97801888) 38°53′30.2734″ N, 76°58′40.868″ W | 3.9231111672194097e+3 | 1.758671230173292e+1 |
| GCJ → WGS | (38.89228416, -77.06177295) 38°53′32.223″ N, 77°3′42.3826″ W | 3.3595587679672776e+3 | 1.33276651294585e+1 |
| BD → WGS | (38.88650101, -77.06814648) 38°53′11.4036″ N, 77°4′5.3273″ W | 3.8993280809969206e+3 | 1.2035535307391196e+1 |
| GCJ →cai WGS | (38.89237090, -77.06166718) 38°53′32.5352″ N, 77°3′42.0018″ W | 3.351557365934842e+3 | 6.806606436223505e-5 |
| BD →cai WGS | (38.88657889, -77.06805138) 38°53′11.684″ N, 77°4′4.985″ W | 3.890530071164795e+3 | 4.395569523697245e-4 |
| GCJ → BD | (38.89475676, -77.01678239) 38°53′41.1243″ N, 77°1′0.4166″ W | 8.559268445970034e+2 | 9.484189662101784e-2 |
| BD → GCJ | (38.88309693, -77.02959721) 38°52′59.1489″ N, 77°1′46.55″ W | 8.502720917154176e+2 | 8.246984401844751e-2 |
| BD →cai GCJ | (38.88309619, -77.02959735) 38°52′59.1463″ N, 77°1′46.5505″ W | 8.503419875829421e+2 | 1.3846253628382624e-4 |
Permalink to this result. Toggle sections: Notes, FAQ, footer. And print.
Notes
- Caijun’s iterative method is included for precise decoding.
It's most useful for bored folks whose GPS data is pretty accurate
and GCJ-02 obfuscation not tainted by the original
LCPRNG.
If you are doing Wikipedia or any kind of archival work, use it to avoid introducing extra error.
- BD is defined in terms of GCJ, hence the last three functions.
- This demo omits the “in China” sanity check. Data regarding
Baidu’s behavior with overseas maps is needed for further
decisions. Observations:
- Unlike Google Maps, Baidu's map in Hong Kong is fully subject to BD-09 ∘ GCJ-02 chained distortions.
- Coordinates in Russia, outside of the sanity check rectangle, uses WGS-84 or and/or friends.
- TODO: check along the boundary.
FAQ
- What is this all about?
- The PRC government requires all local map services to use an obfuscated, deviation-orienated coordinate system. Click on the “restriction” link to read the full Wikipedia article.
- Why should I care?
- With half a kilometer of deviation, GCJ-02 and friends fucks up your Ingress games, causes crazy errors in elevation profiles along cycle routes, and cheerfully leads you into roadside ditches plus a bone fracture.
- Why doesn’t Google/Bing correct its Chinese data served to global users?
- I don’t know. Perhaps they are afraid of getting fined or further kicked out of China. Maybe try OpenStreetMap next time?
- Why are you writing another implementation?
- Because I got bored.
- How does Caijun’s iterative method work?
- Cai has explained the method in full in his R implementation. Go read it, or read Wikipedia.