By Charles Miller
Last week I related a story of how some GPS coordinates unintentionally pointing to somebody’s front yard in Kansas caused some unintended headaches for the people who lived there. I stated that all location data expressed in latitude and longitude are specific, accurate down to an error factor of a few centimeters. There is, however; one country where that does not apply.
The Global Positioning System (GPS) created by the United States is not the only satellite-based navigation system in existence. Russia has its own called Global Navigation Satellite System (GLONASS) and China has its own. The Russian system varies from the American system by a half meter, but the Chinese system might appear to be completely inaccurate.
If you have ever tried using Google Maps or any other popular online mapping web site to look up locations in China you may have noticed that satellite images do not exactly match up with the geographic features on the map. Streets and roads sometimes appear in the middle of rivers while points of interest are not where they really are. This is known as “the Chinese GPS shift problem.” To use a phrase from the Information Technology world: “This is not a bug, it’s a feature!”
The system created by the Chinese State Bureau of Surveying and Mapping uses an obfuscation algorithm to randomly offset coordinates. China has taken the stance that cartographic data of its territory is a matter of national security, and that the public should not have access to the accurate non-randomized data.
To make this situation even thornier, Chinese law states that only authorized entities that are approved by the Chinese Communist Party are allowed to survey and map within China and near its borders. Technically, that could be construed to mean that if you snap a photo with a smart phone while its GPS data is being recorded you have violated Chinese law.
In 2016 the hugely popular Augmented Reality (AR) game Pokemon Go was banned in China. The game uses mobile devices with GPS to locate virtual creatures which appear as if they are in the player’s real-world location. Doing that requires accurate coordinates and in China having accurate geolocation information was illegal, deemed as posing a threat to national security. Apparently even the Great Firewall of China was not able to completely kill consumer demand for Pokemon Go because it was banned for three years and is now legally playable.
Chinese law also requires that all GPS devices obfuscate coordinates, thus making them much less useful than in the west. On the internet there are various groups working to fix the “Chinese GPS shift problem” but this is difficult due to the nature of the obfuscation algorithm, moreover; in China it is against the law to convert obfuscated coordinates to accurate ones.
So, if you get lost in China you might have to deal with it the old fashioned way: stop and ask somebody for directions.
Charles Miller is a freelance computer consultant, a frequent visitor to San Miguel since 1981 and now practically a full-time resident. He may be contacted at 415 101 8528 or email FAQ8@SMAguru.com.
