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Under Chinese law, the use of geographic information in the People's Republic of China is restricted to entities that have special authorization from the administrative department for surveying and mapping under the State Council. Consequences of the restriction include fines for unauthorized surveys, lack of
geotagging Geotagging, or GeoTagging, is the process of adding geographical identification metadata to various media such as a geotagged photograph or video, websites, SMS messages, QR Codes or RSS feeds and is a form of geospatial metadata. This data u ...
information on many cameras when the GPS chip detects a location within China, incorrect alignment of street maps with satellite maps in various applications, and the criminalization of crowdsourced mapping efforts such as
OpenStreetMap OpenStreetMap (OSM) is a free, open geographic database updated and maintained by a community of volunteers via open collaboration. Contributors collect data from surveys, trace from aerial imagery and also import from other freely licensed g ...
. Chinese lawmakers said that these restrictions are to "safeguard the security of China's geographic information". Song Chaozhi, an official of the
State Bureau of Surveying and Mapping The State Bureau of Surveying and Mapping, or the National Bureau of Surveying and Mapping (), was the central agency that was responsible for surveying and mapping in the People's Republic of China (PRC). It was established in 1959 and was made d ...
, said "foreign organizations who wish to carry out mapping or surveying work within China must make clear that they will not touch upon state secrets or endanger state security". Critics outside of China point out that the laws close critical sectors of the Chinese economy to foreign companies, and assist with cracking down on dissent.


Legislation


Surveying

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 Article 1 says: Fines range from 10,000 to 500,000
CNY The renminbi (; symbol: ¥; ISO code: CNY; abbreviation: RMB) is the official currency of the People's Republic of China and one of the world's most traded currencies, ranking as the fifth most traded currency in the world as of April 2022 ...
($ – $ USD). Foreign individuals or organizations that wish to conduct surveying must form a Chinese-foreign joint venture. Between 2006 and 2011, the authorities pursued around 40 illegal cases of mapping and surveying. 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 * March 25, 2008 - China's
State Bureau of Surveying and Mapping The State Bureau of Surveying and Mapping, or the National Bureau of Surveying and Mapping (), was the central agency that was responsible for surveying and mapping in the People's Republic of China (PRC). It was established in 1959 and was made d ...
cracks down on some of the 10,000 websites that publish maps in China, most without authorization. * January 6, 2009 - Chinese authorities fine UK students for “illegal map-making activities”. * 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. * March 14, 2014 - Coca-Cola is accused of illegal mapping. As a consequence, major digital camera manufacturers including Panasonic, Leica, FujiFilm, Nikon and Samsung restrict location information within China.
OpenStreetMap OpenStreetMap (OSM) is a free, open geographic database updated and maintained by a community of volunteers via open collaboration. Contributors collect data from surveys, trace from aerial imagery and also import from other freely licensed g ...
, the
crowdsourced Crowdsourcing involves a large group of dispersed participants contributing or producing goods or services—including ideas, votes, micro-tasks, and finances—for payment or as volunteers. Contemporary crowdsourcing often involves digit ...
project to assemble a map of the world, advises that "private surveying and mapping activities are illegal in China".


Map content

Chinese law and regulations also rule on the contents of any published map: * The 公开地图内容表示若干规定 ("some rules on the content presentation of public maps") of 2003 by the Bureau of Surveying and Mapping (BSM) prohibits the representation of sensitive information such as airports (except those specially listed), military bases, and waterway depths. It also describes the handling and naming of disputed territories and former Qing territories ceded to Russia. * The 公开地图内容表示补充规定(试行)("supplementary rules on the content presentation of public maps, trial version") of 2009 from the BSM additionally prohibits, among other things: ** Locations having a precision of finer than 50 meters and the use of grids finer than 100 meters for elevation data. ** Showing the locations of key infrastructure (power, dams, weather stations) and public safety installations (prisons, mandatory drug rehab facilities). ** Showing the internal structures of airports and ferry ports. ** Showing the weight and height limits of bridges, roads, and tunnels; showing the material of roads. * The 地图管理条例 ("map management regulation") of 2015 from the State Council mandates that all Internet maps must be stored in mainland China, among other rules about national security. The law also details punishments, some of which criminal, for violations. In 2016, a large-scale search by Chinese law enforcement found 253 types of problematic paper maps and 1000 problematic online map websites, most pertaining to the depiction of
Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the no ...
and 9-dash line.


Coordinate systems

Chinese regulations require that approved map service providers in China use a specific coordinate system, called GCJ-02, or Mars Coordinates, which was developed in the Soviet Union and predates the adoption of the universal GPS standard.
Baidu Maps Baidu Maps is a desktop and mobile web mapping service application and technology provided by Baidu, offering satellite imagery, street maps, street view ("Panorama" - :zh:百度全景) and indoor view perspectives, as well as functions such ...
uses yet another coordinate system - BD-09, which seems to be based on GCJ-02.


GCJ-02

GCJ-02 (Officially ) is a
geodetic datum A geodetic datum or geodetic system (also: geodetic reference datum, geodetic reference system, or geodetic reference frame) is a global datum reference or reference frame for precisely representing the position of locations on Earth or other pla ...
used by the Chinese
State Bureau of Surveying and Mapping The State Bureau of Surveying and Mapping, or the National Bureau of Surveying and Mapping (), was the central agency that was responsible for surveying and mapping in the People's Republic of China (PRC). It was established in 1959 and was made d ...
(), and based on WGS-84. It uses an obfuscation algorithm which adds apparently random offsets to both the latitude and longitude, with the alleged goal of improving national security. There is a license fee associated with using this mandatory algorithm in China. A marker with GCJ-02 coordinates will be displayed at the correct location on a GCJ-02 map. However, the offsets can result in a 100–700 meter error from the actual location if a WGS-84 marker (such as a GPS location) is placed on a GCJ-02 map, or vice versa. The
Google Maps Google Maps is a web mapping platform and consumer application offered by Google. It offers satellite imagery, aerial photography, street maps, 360° interactive panoramic views of streets (Street View), real-time traffic conditions, and rou ...
street map is offset by 50–500 meters from its satellite imagery.
Yahoo! Maps Yahoo! Maps was a free online mapping portal provided by Yahoo! Functionality included local weather powered by The Weather Channel, printing maps, and local reviews powered by Yelp. It shut down on June 30, 2015. For a time in 2019, Yahoo! Maps ...
also displayed the street map without major errors when compared to the satellite imagery. MapQuest overlays OpenStreetMap data perfectly as well. Despite the secrecy surrounding the GCJ-02 obfuscation, several open-source projects exist that provide conversions between GCJ-02 and WGS-84, for languages including C#, C, Go, Java, JavaScript, PHP, Python, R, and Ruby. They appear to be based on leaked code for the WGS to GCJ part. Other solutions to the conversion involve interpolating coordinates based on regression from a data set of Google China and satellite imagery coordinates. An attempt by Wu Yongzheng using
fast Fourier transform A fast Fourier transform (FFT) is an algorithm that computes the discrete Fourier transform (DFT) of a sequence, or its inverse (IDFT). Fourier analysis converts a signal from its original domain (often time or space) to a representation in ...
analysis gave a result much like the leaked code. From the leaked code, GCJ-02 uses parameters from the SK-42 reference system. The parameters were used to calculate lengths of one degree of
latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north ...
and
longitude Longitude (, ) is a geographic coordinate that specifies the east– west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek let ...
, so that offsets in meters previously calculated can be converted to degrees for the WGS-84 input coordinates.


BD-09

BD-09 is a geographic coordinate system used by
Baidu Maps Baidu Maps is a desktop and mobile web mapping service application and technology provided by Baidu, offering satellite imagery, street maps, street view ("Panorama" - :zh:百度全景) and indoor view perspectives, as well as functions such ...
, adding further obfuscation to GCJ-02 "to better protect users' privacy". Baidu provides an API call to convert from Google or GPS (WGS-84), GCJ-02, BD-09, or coordinates into Baidu or GCJ-02 coordinates. As required by local law, there is no API to convert into WGS-84, but open source implementations in R and various other languages exist.


Reverse transformation

As the actual algorithm is now available in open source form (see above), the text below is obsolete. GCJ-02 appears to use multiple high-frequency noises of the form 20n \sin(180 k \times lat_), effectively generating a transcendental equation and thus eliminating analytical solutions. However, the open-source "reverse" transformations make use of the properties of GCJ-02 that the transformed coordinates are not too far from WGS-84 and are mostly monotonic related to corresponding WGS-84 coordinates: 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 = bad improvement = 99 + 99j # dummy value while abs(improvement) > eps: improvement = worsen(wgs) - bad wgs = wgs - improvement return wgs The rough method is reported to give some 1~2 meter accuracy for wgs2gcj, while the exact ( fixed point iteration) method is able to get "centimeter accuracy" in two calls to the forward function.Alt URL
/ref> Since the two properties ensure some basic functionality of the coordinate system, it is unlikely that the methods will change with new coordinate systems. The BD-to-GCJ code works in a manner much like the rough method, except that it removes the explicitly-applied constant shift of ~20 seconds of arc on both coordinates first and works in polar coordinates like the forward function does. The establishment of working conversion methods both ways largely renders obsolete datasets for deviations mentioned below.


GPS shift problem

The China GPS shift (or offset) problem is a class of issues stemming from the difference between the GCJ-02 and WGS-84
datum In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted. ...
s.
Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite ...
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. Satellite imagery and user-contributed street map data sets, such as those from
OpenStreetMap OpenStreetMap (OSM) is a free, open geographic database updated and maintained by a community of volunteers via open collaboration. Contributors collect data from surveys, trace from aerial imagery and also import from other freely licensed g ...
also display correctly because they have been collected using GPS devices (albeit technically illegally – see
Legislation Legislation is the process or result of enrolling, enacting, or promulgating laws by a legislature, parliament, or analogous governing body. Before an item of legislation becomes law it may be known as a bill, and may be broadly referred to ...
). Some map providers, such as
Here Here is an adverb that means "in, on, or at this place". It may also refer to: Software * Here Technologies, a mapping company * Here WeGo (formerly Here Maps), a mobile app and map website by Here Television * Here TV (formerly "here!"), a ...
, choose to also offset their satellite imagery layer to match the GCJ-02 street map. Google has worked with Chinese
location-based service A location-based service (LBS) is a general term denoting software services which use geographic data and information to provide services or information to users. LBS can be used in a variety of contexts, such as health, indoor object search, en ...
provider AutoNavi since 2006 to source its maps in China. Google uses GCJ-02 data for the street map, but does not shift the satellite imagery layer, which continues to use WGS-84 coordinates, 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. Overlaying GPS tracks on
Google Maps Google Maps is a web mapping platform and consumer application offered by Google. It offers satellite imagery, aerial photography, street maps, 360° interactive panoramic views of streets (Street View), real-time traffic conditions, and rou ...
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 Maps uses GCJ-02. The issue has been reported numerous times on the Google Product Forums since 2009, with 3rd party applications emerging to fix it. Data sets with offsets for large lists of Chinese cities existed for sale. 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.


Hong Kong and Macau

Under One Country Two Systems, legislation in mainland China does not apply in
Hong Kong Hong Kong ( (US) or (UK); , ), officially the Hong Kong Special Administrative Region of the People's Republic of China (abbr. Hong Kong SAR or HKSAR), is a List of cities in China, city and Special administrative regions of China, special ...
and
Macau Macau or Macao (; ; ; ), officially the Macao Special Administrative Region of the People's Republic of China (MSAR), is a city and special administrative region of China in the western Pearl River Delta by the South China Sea. With a pop ...
SARs Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by the severe acute respiratory syndrome coronavirus (SARS-CoV or SARS-CoV-1), the first identified strain of the SARS coronavirus species, ''seve ...
and there are no similar restrictions in the SARs. Therefore, the GPS shift problem does not apply. However, at the border between the SARs and mainland China, the data shown by online maps are broken where the shifted data and correct data overlap. This poses problems to users travelling across the border, especially visitors not aware of the issue.


See also

*
Geographic information systems in China Geographic Information Systems (GIS) are an increasingly important component of business, healthcare, security, government, trade, media, transportation and tourism industries and operations in China. GIS software is playing an increasing role in ...


Notes


References

{{Censorship in China Censorship in China Internet censorship in China Web mapping Geographic data and information regulation