Baidu Maps

• Mainland China
• Hong Kong
• Macau

• September 2005 - Baidu Maps is released
• 2010 - Baidu adds a unique 3D highly detailed view for select cities, very similar to the computer game SimCity.[7] The images are licensed from digital mapping service Edushi.[8] Cities being currently covered include Beijing, Shanghai, Guangzhou and Shenzhen.
• November 2011 - Baidu launches satellite imagery with much better resolution for the Greater China region than Google Maps[9] City-level only includes Beijing, Shanghai, Guangzhou, Shenzhen, Hong Kong, Macao and other major cities.
• September 3, 2012 - at its annual Baidu World event, Baidu reveals 360-degree digital imagery for select buildings[8]

Screenshot of Baidu Map with WGS-84, GCJ-02 and BD-09 markers

Baidu Map uses a variant of web Mercator projection for slicing map data into tiles, with distances expressed in degrees. It's associated with an underlying latitude-longitude reference. However, the reference uses the BD-09 coordinate system, which adds further obfuscation to the already obfuscated national standard in China, GCJ-02[10] (which in turn is defined in terms of the de facto standard around the world, WGS 84). Baidu alleges that adopting BD-09 "protects users' privacy".[11]

The Baidu Map API documentation specifies that "real" (WGS-84) GPS coordinates must be converted via a coordinate conversion interface.[12] An HTTP interface, JavaScript API, Android SDK, and iOS SDK are available.

The JavaScript coordinate conversion API is demonstrated online by Baidu, but without any reverse (to GCJ-02) conversion capabilities.[13] Open source implementations in R [14] and various other languages[15] exist, implemented in a manner much like the reverse GCJ-02 algorithm.

BD-09's lat-lon coordinates are derived by scrambling a polar version of GCJ-02 coordinates and adding a fixed offset:[14]

from cmath import polar, rect
from math import sin, cos, pi
# Represent coordinates with complex numbers for simplicity
coords = complex

# baidu assumes x/real: lon; y/imag: lat here.
def gcj_bd(gcj: coords) -> coords:
    r, θ = polar(gcj)
    r += 2e-5 * sin(gcj.imag * pi * 3000 / 180)
    θ += 3e-6 * cos(gcj.real * pi * 3000 / 180)
    return rect(r, θ) + (0.0065 + 0.006j)

The street view service of Baidu Maps was first launched on August 21, 2013.[16] This is a list of cities supported as of March 11, 2015:

• Baidu Maps
• Baidu Map API example plotting markers with WGS-84, GCJ-02 and BD-09 coordinates