Restrictions on geographic data in China

According to articles 7, 26, 40 and 42 of the Surveying and Mapping Law of the People's Republic of China, private surveying and mapping activities have been illegal in mainland China since 2002. The law prohibits

publishing, without authorization, significant geographic information and data concerning the territorial air, land and waters, as well as other sea areas under the jurisdiction of the People's Republic of China.

— The National Administration of Surveying, Mapping and Geoinformation of China, Surveying and Mapping Law of the People’s Republic of China

Article 1 says:

This Law is enacted to strengthen the administration of the surveying and mapping undertaking, promote its development and ensure that it renders service to development of the national economy, the building up of national defence, and progress of the society.[3]

Fines range from 10,000 to 500,000 CNY ($1447 – $72359 USD). Foreign individuals or organizations that wish to conduct surveying must form a Chinese-foreign joint venture.[1]

Between 2006 and 2011, the authorities pursued nearly 40 illegal cases of mapping and surveying.[4] The media has reported on other cases of unlawful surveys:

• March 7, 2007 - Japanese and Korean scholars fined; joint-venture Weihai hired foreign surveyors without approval from the government[5]
• March 25, 2008 - China's State Bureau of Surveying and Mapping cracks down on some of the 10,000 websites that publish maps in China, most without authorization.[6]
• January 6, 2009 - Chinese authorities fine UK students for “illegal map-making activities”.[7]
• 2010 - Chinese authorities to crack down on the unregistered or illegal among 42,000 online map providers, targeting incorrect information and leaks of sensitive information involving state secrets. New standards require all Internet map providers to keep servers storing map data inside China.[8]
• March 14, 2014 - Coca-Cola is accused of illegal mapping.[9]

As a consequence, major digital camera manufacturers including Panasonic, Leica, FujiFilm, Nikon and Samsung restrict location information within China.[10]

OpenStreetMap, the crowdsourced project to assemble a map of the world, advises that "private surveying and mapping activities are illegal in China".[11]

Geodesy
Fundamentals Geodesy Geodynamics Geomatics History
Concepts Geographical distance Geoid Figure of the Earth (Earth radius and Earth's circumference) Geodetic datum Geodesic Geographic coordinate system Horizontal position representation Latitude / Longitude Map projection Reference ellipsoid Satellite geodesy Spatial reference system Spatial relations
Technologies Global Nav. Sat. Systems (GNSSs) Global Pos. System (GPS) GLONASS (Russia) BeiDou (BDS) (China) Galileo (Europe) NAVIC (India) Quasi-Zenith Sat. Sys. (QZSS) (Japan) Discrete Global Grid and Geocoding
Standards (history) NGVD 29 Sea Level Datum 1929 OSGB36 Ordnance Survey Great Britain 1936 SK-42 Systema Koordinat 1942 goda ED50 European Datum 1950 SAD69 South American Datum 1969 GRS 80 Geodetic Reference System 1980 ISO 6709 Geographic point coord. 1983 NAD 83 North American Datum 1983 WGS 84 World Geodetic System 1984 NAVD 88 N. American Vertical Datum 1988 ETRS89 European Terrestrial Ref. Sys. 1989 GCJ-02 Chinese obfuscated datum 2002 Geo URI Internet link to a point 2010 International Terrestrial Reference System Spatial Reference System Identifier (SRID) Universal Transverse Mercator (UTM)

JavaScript implementation of coordinate "processing" methods used in China

Technical spatial processing must be applied to electronic navigational maps prior to publication, sales, redistribution, and usage.

— GB 20263―2006 "Basic security processes for electronic navigational maps", 4.1

Chinese regulations mandate that approved map service providers in China use a specific coordinate system, called GCJ-02. Baidu Maps uses yet another coordinate system - BD-09,[12][13] which seems to be based on GCJ-02.[14]

from typing import Callable

# Represent coordinates with complex numbers for simplicity
coords = complex
# Coords-to-coords function
C2C = Callable[[coords], coords]

def rev_transform_rough(bad: coords, worsen: C2C) -> coords:
    """Roughly reverse the ``worsen`` transformation.

    Since ``bad = worsen(good)`` is close to ``good``,
    ``worsen(bad) - bad`` can be used to approximate ``bad - good``.

    First seen in eviltransform.
    """
    return bad - (worsen(bad) - bad)

def rev_transform(bad: coords, worsen: C2C) -> coords:
    """More precisely reverse the ``worsen`` transformation.

    Similar to ``rev_transform_rough``,
    ``worsen(a) - worsen(b)`` can be used to approximate ``a - b``.

    First seen in geoChina/R/cst.R (caijun 2014).
    Iteration-only version (without rough initialization) has been known
    since fengzee-me/ChinaMapShift (November 2013).
    """
    eps = 1e-6
    wgs = rev_transform_rough(bad, worsen)
    improvement = 99 + 99j  # dummy value

    while abs(improvement) > eps:
        improvement = worsen(wgs) - bad
        wgs = wgs - improvement
    return wgs

Google Maps displays satellite imagery using the WGS-84 coordinate system, and street maps using the GCJ-02 datum

The China GPS shift (or offset) problem is a class of issues stemming from the difference between the GCJ-02 and WGS-84 datums. Global Positioning System coordinates are expressed using the WGS-84 standard and when plotted on street maps of China that follow the GCJ-02 coordinates, they appear off by a large (often over 500 meters) and variable amount. Authorized providers of location-based services and digital maps (such as AutoNavi or NavInfo) must purchase a "shift correction" algorithm that enables plotting GPS locations correctly on the map.[35] Satellite imagery and user-contributed street map data sets, such as those from OpenStreetMap also display correctly because they have been collected using GPS devices (albeit technically illegally - see Legislation).

Some map providers, such as Here, choose to also offset their satellite imagery layer to match the GCJ-02 street map.[36]

Google has worked with Chinese location-based service provider AutoNavi since 2006 to source its maps in China.[37] google.cn/maps (formerly Google Ditu) uses the GCJ-02 system for both its street maps[38] and satellite imagery.[39] However, the WGS-84 positions reported by a browser are depicted at the wrong positions. On the contrary, google.com/maps also uses GCJ-02 data for the street map, but does not shift the satellite imagery layer, which continues to use WGS-84 coordinates,[40] with the benefit that WGS-84 positions can still be overlaid correctly on the satellite image (but not the street map). Google Earth also uses WGS-84 to display the satellite imagery.[41]

Overlaying GPS tracks on Google.com Maps and any street maps sourced from Google.com via its API, will lead to a similar display offset problem, because GPS tracks use WGS-84, and Google.com maps use GCJ-02. The issue has been reported numerous times on the Google Product Forums since 2009,[42] with 3rd party applications emerging to fix it.[43] Data sets with offsets for large lists of Chinese cities existed for sale.[44] The problem was observed as early as 2008, and the causes were unclear, with (misguided) speculation that imported GPS chips were tampered with code that caused incorrect reporting of coordinates.[45]

• Geographic information systems in China