Due to national security issues, the use of geographical information in China is restricted to entities that have special authorization from administrative departments for surveys and mapping under the State Council. Consequences of restrictions include fines for unauthorized surveys, lack of geotagged information on many cameras when GPS chips detect locations in China, misalignment of road maps with satellite maps in various applications, and appear to violate the laws of crowdsourced mapping efforts such as OpenStreetMap.
Video Restrictions on geographic data in China
Legislasi
According to articles 7, 26, 40 and 42 of the Survey and Mapping of the People's Republic of China , private survey and mapping activities have been illegal in mainland China since 2002. The law forbids
publication, without authorization, significant geographical information and data on air, land and water, and other marine territories under the jurisdiction of the People's Republic of China.
Fines range from 10,000 to 500,000 CNY (1479 - 73964 USD). Individuals or foreign organizations wishing to conduct the survey should establish a Chinese-foreign joint venture.
Between 2006 and 2011, the authorities pursued nearly 40 cases of mapping and illegal surveys. The media has reported other cases of unlawful surveys:
- 2007 March 7 - Japanese and Korean students fined; joint-venture Weihai hire foreign surveyors without government approval
- 2008 March 25 - China's Country Survey and Mapping Bureau knocked out some of the 10,000 websites that publish maps in China, mostly without permission.
- 2009 January 6 - Chinese authorities fine a British student for "illegal map making".
- 2010 - Chinese authorities for unregistered or illegal action among 42,000 online map providers, targeting false information and leaking sensitive information involving state secrets. The new standard requires all Internet map providers to store servers that store map data in China.
- 2014 March 14 - Coca-Cola accused of illegal mapping.
As a result, major digital camera manufacturers including Panasonic, Leica, FujiFilm, Nikon and Samsung are limiting location information in China.
OpenStreetMap, a crowdsourced project to compile a world map, suggested that "surveying and personal mapping activities are illegal in China".
Maps Restrictions on geographic data in China
Coordinate system
Technical spatial processing should be applied to electronic navigation maps prior to publication, sale, redistribution, and usage.
Chinese regulations mandate that approved map service providers in China use a particular coordinate system, called GCJ-02. Baidu Maps uses another coordinate system - BD-09, which seems to be based on GCJ-02.
GCJ-02
GCJ-02 (the everyday language Mars ) is a geodetic datum formulated by the China Mapping and Mapping Bureau (Mandarin: ?? ; pinyin: guÃÆ'³-cÃÆ'¨-jÃÆ'º ), and based on WGS-84. It uses an obfuscation algorithm that adds a random offset to latitude and longitude, with a view to increasing national security goals.
Markers with GCJ-02 coordinates will be displayed in the correct location on the GCJ-02 map. However, offsets can generate errors 100 - 700 meters from the actual location if the WGS-84 marker (such as GPS location) is placed on the GCJ-02 map, or vice versa. The Google.com roadmap is offset by 50-500 meters from its satellite imagery, while the Google.cn map does not. Yahoo! The map also shows a road map with no major errors when compared to satellite imagery. MapQuest superimposes OpenStreetMap data as well.
Regardless of the confidentiality surrounding GCJ-02 chats, several open-source projects exist that provide conversion between GCJ-02 and WGS-84, for languages ​​including C #, C, Go, Java, JavaScript, PHP, Python, R, and Ruby. They seem to be based on leaked code for the WGS section into GCJ. Another solution to conversion involves interpolation coordinates based on regressions from Google China's data set and satellite image coordinates. An attempt by Wu Yongzheng using FFT analysis gives results like leaked code.
From the leaked code, GCJ-02 uses the parameters of the SK-42 reference system. Parameters are used to calculate the length of one degree of latitude and longitude, so that offsets in previously calculated meters can be converted to degrees for WGS-84 input coordinates.
BD-09
BD-09 is the geographic coordinate system used by Baidu Maps, adding further obscurity to the vague GCJ-02 "to better protect user privacy". Baidu provides API calls to convert from Google or GPS (WGS-84) coordinates to Baidu coordinates. Similar to GCJ-02, there is no API to convert in the other direction, but open source implementations in R and various other languages ​​exist.
Inverted transformation
GCJ-02 tampaknya menggunakan beberapa suara frekuensi tinggi dari bentuk , secara efektif menghasilkan persamaan transendental dan dengan demikian menghilangkan solusi analitik. Namun, transformasi "reverse" open-source memanfaatkan sifat-sifat GCJ-02 bahwa koordinat yang diubah tidak terlalu jauh dari WGS-84 dan sebagian besar monotonik terkait dengan koordinat WGS-84 yang sesuai:
The crude method is reported to provide an accuracy of 1 ~ 2 meters for wgs2gcj, whereas fixed iteration methods can obtain "centimeter accuracy" in two calls to the front function. Since both properties ensure some of the basic functions of the coordinate system, it is likely that the method will not change with the new coordinate system. The BD-to-GCJ code works in a manner similar to the rough method, except that it removes constantly applied constant shifts of ~ 20 arcseconds on both the first coordinates and works in polar coordinates like the front function does.
The formation of a second way conversion method works largely to eliminate the dataset for the aberrations mentioned below.
China GPS shift problem
The problem of China GPS shift (or offset) is the problem class that comes from the difference between GCJ-02 and WGS-84 data. The coordinates of the Global Positioning System are expressed using WGS-84 standards and when plotted on a Chinese roadmap following the GCJ-02 coordinates, those coordinates appear large (often over 500 meters) and the number of variables. Official providers of location-based services and digital maps (such as AutoNavi or NavInfo) must purchase a "shift correction" algorithm that enables planning the GPS location correctly on the map. Satellite images and user-contributed road map data, such as from OpenStreetMap, are also displayed correctly because they have been collected using GPS devices (although technically illegal - see Legislation).
Some map providers, such as Here, choose to also offset their satellite imagery layers to match the GCJ-02 roadmap.
Google has been working with China's LBS provider, AutoNavi since 2006 to create maps in China. google. cn /maps (formerly Google Ditu) uses GCJ-02 system for both road maps and satellite imagery. However, the WGS-84 position reported by the browser is depicted in the wrong position. Instead, google. com /maps also uses GCJ-02 data for the road map, but does not shift the satellite imagery layer, which continues to use WGS-84 coordinates, with the benefit that the WGS-84 position can still be properly coated on satellite imagery (but not a roadmap). Google Earth also uses WGS-84 to display satellite imagery.
Overlaying GPS tracks on Google.com Maps and any roadmap sourced from Google.com through its APIs will lead to similar display offset issues, as GPS tracks use WGS-84, and Google.com maps using GCJ-02. This issue has been reported many times in the Google Product Forums since 2009, with 3rd-party apps appearing to fix it. Data sets with offsets for a large list of Chinese cities are there for sale. The problem was observed in early 2008, and the cause is unclear, with speculation (misguided) that imported GPS chips are corrupted with code that causes incorrect coordinate reporting.
Hong Kong and Macau
Under One Two-State System, laws in mainland China do not apply in Hong Kong and Macau SAR and there are no similar restrictions on SAR. Therefore, GPS shift issues are not applicable. However, on the border between SAR and mainland China, the data indicated by the online map is damaged where data shifts and the correct data overlaps. This poses a problem for users traveling across the border, especially visitors who are not aware of the issue.
Note
References
Source of the article : Wikipedia
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