Input
Results
| Operation | Result | ΔObfs/m | ΔRoundtrip/m |
|---|---|---|---|
| WGS → GCJ | (38.90014723, -77.01551267) 38°54′0.53″ N, 77°0′55.8456″ W | 3.35253468857235e+3 | 1.4649074311936825e+1 |
| WGS → BD | (38.90608930, -77.00906142) 38°54′21.9215″ N, 77°0′32.6211″ W | 3.898410001291045e+3 | 1.4587253336010123e+1 |
| GCJ → WGS | (38.90705277, -77.09248733) 38°54′25.39″ N, 77°5′32.9544″ W | 3.352373791044091e+3 | 6.167319159614701e+0 |
| BD → WGS | (38.90116985, -77.09890157) 38°54′4.2115″ N, 77°5′56.0457″ W | 3.8948873574465065e+3 | 4.515969546276611e+0 |
| GCJ →cai WGS | (38.90709423, -77.09244006) 38°54′25.5392″ N, 77°5′32.7842″ W | 3.3488407477904216e+3 | 2.332576300329193e-6 |
| BD →cai WGS | (38.90120127, -77.09886779) 38°54′4.3246″ N, 77°5′55.924″ W | 3.891729401352714e+3 | 2.2625170341128407e-4 |
| GCJ → BD | (38.90943673, -77.04760359) 38°54′33.9722″ N, 77°2′51.3729″ W | 8.529665578222582e+2 | 9.962094904736195e-2 |
| BD → GCJ | (38.89770313, -77.06043010) 38°53′51.7313″ N, 77°3′37.5484″ W | 8.59979050773051e+2 | 8.774714954827177e-2 |
| BD →cai GCJ | (38.89770385, -77.06042966) 38°53′51.7339″ N, 77°3′37.5468″ W | 8.598943056816308e+2 | 5.424717850504178e-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.