Gaia GPS
  • 7-Day Free Trial Gaia GPS Premium
  • Out and Back Podcast
    • Gaia GPS

      Everything You Need to Know About Satellite Communicators

      December 1, 2022

      Adventures

      How to Avoid Another Deadly Avalanche Season

      January 21, 2022

      Gaia GPS

      The Best Advice We Received in 2021

      December 26, 2021

      Gaia GPS

      Avalanche Safety with Snow Science Expert Bruce Tremper

      November 30, 2021

      Gaia GPS

      Planning a Thru-Hike Next Year? Here’s What You…

      October 21, 2021

      Gaia GPS

      A Definitive Guide to the Best Camp Coffee

      September 30, 2021

      Gaia GPS

      Owls and UFOs with Ultralight Expert Mike Clelland

      September 9, 2021

  • Offroad Podcast
    • Gaia GPS

      Cook Marco Hernandez’s Mouthwatering Camp Meals

      January 25, 2023

      Gaia GPS

      Monique Song: How a City Girl Became the…

      April 7, 2022

      Gaia GPS

      TrailRecon Explains How to Become an Overlander Overnight

      March 9, 2022

      Adventures

      How to Stay Married on a Long-Distance Adventure

      February 9, 2022

      Adventures

      How to Go From ‘Desk to Glory’ in…

      January 12, 2022

      Gaia GPS

      The Best Advice We Received in 2021

      December 26, 2021

      Gaia GPS

      Gaia GPS’s Best New Overlanding Maps and Features…

      December 23, 2021

  • Adventures
    • User Stories
  • Activities
    • Backcountry Skiing
    • Boating
    • Emergency Response
    • Fishing
    • Offroading
  • New Features
    • Gaia GPS

      Book Campsites Right From Gaia GPS

      February 23, 2023

      Gaia GPS

      Our Favorite New Maps and Features

      December 23, 2022

      Gaia GPS

      OpenSnow Weather Now Available at-a-Tap on the Map

      November 9, 2022

      Backcountry Skiing

      Find the Deepest, Lightest Powder with the Snow…

      November 8, 2022

      Gaia GPS

      New Edit Tools: Creating Your Own Routes Just…

      September 1, 2022

      Gaia GPS

      Top 10 Ways to Use Waypoints

      August 30, 2022

      Gaia GPS

      Meet Map Packs: A Totally New Way to…

      May 9, 2022

  • New Maps
    • Gaia GPS

      Why NatGeo Trails Illustrated are America’s Favorite Maps

      February 9, 2023

      Backcountry Skiing

      New! Find Backcountry Skiing in Gaia Winter Map

      January 11, 2023

      Gaia GPS

      Our Favorite New Maps and Features

      December 23, 2022

      Gaia GPS

      Spy Avalanche Terrain with Higher Res Slope Angle…

      December 14, 2022

      Backcountry Skiing

      Find the Deepest, Lightest Powder with the Snow…

      November 8, 2022

      Gaia GPS

      Activate Snow Mode with Gaia Winter

      October 26, 2022

      Adventures

      Take a Trip to Baja California with Nat…

      September 13, 2022

  • Home
Gaia GPS
  • 7-Day Free Trial Gaia GPS Premium
  • Out and Back Podcast
    • Gaia GPS

      Everything You Need to Know About Satellite Communicators

      December 1, 2022

      Adventures

      How to Avoid Another Deadly Avalanche Season

      January 21, 2022

      Gaia GPS

      The Best Advice We Received in 2021

      December 26, 2021

      Gaia GPS

      Avalanche Safety with Snow Science Expert Bruce Tremper

      November 30, 2021

      Gaia GPS

      Planning a Thru-Hike Next Year? Here’s What You…

      October 21, 2021

      Gaia GPS

      A Definitive Guide to the Best Camp Coffee

      September 30, 2021

      Gaia GPS

      Owls and UFOs with Ultralight Expert Mike Clelland

      September 9, 2021

  • Offroad Podcast
    • Gaia GPS

      Cook Marco Hernandez’s Mouthwatering Camp Meals

      January 25, 2023

      Gaia GPS

      Monique Song: How a City Girl Became the…

      April 7, 2022

      Gaia GPS

      TrailRecon Explains How to Become an Overlander Overnight

      March 9, 2022

      Adventures

      How to Stay Married on a Long-Distance Adventure

      February 9, 2022

      Adventures

      How to Go From ‘Desk to Glory’ in…

      January 12, 2022

      Gaia GPS

      The Best Advice We Received in 2021

      December 26, 2021

      Gaia GPS

      Gaia GPS’s Best New Overlanding Maps and Features…

      December 23, 2021

  • Adventures
    • User Stories
  • Activities
    • Backcountry Skiing
    • Boating
    • Emergency Response
    • Fishing
    • Offroading
  • New Features
    • Gaia GPS

      Book Campsites Right From Gaia GPS

      February 23, 2023

      Gaia GPS

      Our Favorite New Maps and Features

      December 23, 2022

      Gaia GPS

      OpenSnow Weather Now Available at-a-Tap on the Map

      November 9, 2022

      Backcountry Skiing

      Find the Deepest, Lightest Powder with the Snow…

      November 8, 2022

      Gaia GPS

      New Edit Tools: Creating Your Own Routes Just…

      September 1, 2022

      Gaia GPS

      Top 10 Ways to Use Waypoints

      August 30, 2022

      Gaia GPS

      Meet Map Packs: A Totally New Way to…

      May 9, 2022

  • New Maps
    • Gaia GPS

      Why NatGeo Trails Illustrated are America’s Favorite Maps

      February 9, 2023

      Backcountry Skiing

      New! Find Backcountry Skiing in Gaia Winter Map

      January 11, 2023

      Gaia GPS

      Our Favorite New Maps and Features

      December 23, 2022

      Gaia GPS

      Spy Avalanche Terrain with Higher Res Slope Angle…

      December 14, 2022

      Backcountry Skiing

      Find the Deepest, Lightest Powder with the Snow…

      November 8, 2022

      Gaia GPS

      Activate Snow Mode with Gaia Winter

      October 26, 2022

      Adventures

      Take a Trip to Baja California with Nat…

      September 13, 2022

  • Home

Gaia GPS & China’s GPS Restrictions

by Kate Dougherty February 8, 2016
by Kate Dougherty February 8, 2016

In the interest of national security, the Chinese government strictly controls geographic data, and deliberately skews maps of the country to protect sensitive buildings and facilities. These restrictions cause offsets in the data when using GPS navigation or digital maps, but the OpenStreetMap (OSM) based maps in Gaia GPS don’t have this problem, and this makes apps like Gaia GPS popular in China.

You can find hiking, cycling, and topo maps based on OpenStreetMap in Gaia GPS. Check out these Knowledge Base links to learn how to change your visible layer to an OSM-based source in the iOS or Android versions of Gaia GPS.

Apple Maps Work, but iOS Photos and Apps Have Issues

Because Apple is an authorized mobile provider that has purchased a “shift correction algorithm,” Apple Maps will display your current location correctly on an iPhone. However, the GPS offset still causes a number of problems on iOS devices:

  • Your phone will offset geotagged photos. Similarly, some cameras with GPS chips may not display coordinates for users in China either.
  • Google Maps will only display the correct location on an Android phone, an iPhone user who recently visited China explained.
  • Apps that show your friends’ whereabouts will offset their locations by 300-500 meters, or about a block or two.

GPS, Mapping, and Chinese Law

OSM’s contributors build the map by collecting GPS traces and by tracing features from satellite imagery. Despite legal restrictions, a lot of this mapping has been done in China. Our recent blog post explains how to contribute to OSM, but keep in mind that due to restrictions on private mapping activities, doing so in China is illegal.

The restrictions apply to all types of geographic data; the country’s Surveying and Mapping Law effectively makes private surveying and mapping off-limits in mainland China. While the government has provisions for academic research, foreigners must obtain approval from the State Council and partner with the relevant authorities when conducting fieldwork. Individuals who break the rules can face confiscation of equipment, interrogation, and even jail time. China takes the matter very seriously, as evidenced by the nearly 40 illegal mapping cases it prosecuted from 2006-2011. Law enforcement has detained and questioned geologists and other scientists for recording what they believed to be innocuous GPS coordinates for their research.

How to Circumvent the GPS Restrictions in China

When you’re on the ground in China, using an OSM-based map is the best way to get accurate locations. In addition, if you’re a programmer working with geotagged photos or other geodata, there are several open source scripts that can help you convert WGS coordinates to GCJ-02.

Programmers can choose from scripts in C#, R, Python, PHP, Ruby, and Objective-C to georeference locations correctly. While the authors of the scripts probably used leaked code to create them, other solutions use the accurately aligned data from the Chinese version of Google Maps. Some fixes use statistical regression to interpolate GWS-84 coordinates from this version.

Did You Know? Google Maps and Displacement

You may notice the displacement when using satellite imagery in Google Maps (compared to a road map), and particularly when looking at major roads. For example, in the screen shot below, Google offsets the marked highway interchanges near the Capital Library and Beijing Vansha Outlets Shopping Center to the northeast on the street map.

Misaligned interchanges and major roads in Beijing. Credit: Google Inc.

Misaligned interchanges and major roads in Beijing. Credit: Google Inc.

This is because location-based service providers like Google must obtain authorization from the Chinese government to offer digital street maps of China, and buy a “shift correction” algorithm. In order to comply with the law, these companies must use the country’s proprietary, encrypted GCJ-02 coordinate system, rather than the most commonly used WGS-84 system. The satellite imagery uses the “true” coordinate system, while the street map uses the skewed Chinse system. Dan Dascalescu investigated this shift by searching maps.google.com for the known WGS coordinates of the Monument to the People’s Heroes in Shanghai (31.24427 N, 121.48695 E).

Google’s street map retrieves a location in the middle of the Wusong River, while in reality you’ll find the monument several hundred meters to the southeast, at the intersection of the Wusong and Huangpu Rivers.

Searching on known WGS latitude and longitude coordinates for a Chinese landmark retrieves an incorrect location in Google Maps. Credit: Google Inc.

Searching on known WGS latitude and longitude coordinates for a Chinese landmark retrieves an incorrect location in Google Maps. Credit: Google Inc.

Activating the satellite imagery reveals pronounced misalignment, as shown in the screenshot below. The marker appears in the correct position on the imagery.

Google.com street maps do not align with satellite imagery in China. Credit: Google Inc.

Google.com street maps do not align with satellite imagery in China. Credit: Google Inc.

Apple Maps has the same displacement issue. Searching on the WGS coordinates will pinpoint the correct location on the imagery, but not on the map. Apple doesn’t display the street map’s road network when imagery is activated, which makes the effect less jarring. Still, the bevvy of hotels it displays in the middle of the Wusong River give the displacement away.

Apple Maps also mismatches satellite imagery and road maps in China. Credit: Apple Inc.

Apple Maps also mismatches satellite imagery and road maps in China. Credit: Apple Inc.

The misalignment does not appear on the Chinese version of Google Maps, since both the imagery and the map use the state-mandated coordinate system. Users can pinpoint the correct location of the monument on both sources by searching for the GCJ-02 coordinates (31.2423 N, 121.4914 E). Similarly, maps from the Chinese company Baidu line up correctly. In addition, manufacturers evidently modify GPS devices sold in China to align with GCJ-02 maps. “It is still unclear whether GPS chips manufactured in China return GCJ-02 coordinates directly to match approved Chinese maps, or if they return WGS-84 coordinates, which authorized map software providers can convert to GCJ-02,” a Wikipedia article on the subject states.

The Chinese version of Google Maps shows the monument in the correct location on both the imagery and the street map when a user searches for its GCJ-02 coordinates. Credit: Google Inc.

The Chinese version of Google Maps shows the monument in the correct location on both the imagery and the street map when a user searches for its GCJ-02 coordinates. Credit: Google Inc.

However, because the cartographic regulations do not apply in the special administrative regions (SAR) of Macau and Hong Kong, Google will always scramble the map at the borders of these SARS and mainland China.

China’s GPS Restrictions - Google Maps near the Hong-Kong-Shenzhen border. Credit: Google Inc.

Google Maps near the Hong-Kong-Shenzhen border. Credit: Google Inc.

chinagpsmapsrestrictions
0
FacebookTwitterRedditEmail
Kate Dougherty

previous post
Meet the Gaia GPS Team – Jesse Crocker
next post
Welcome Jason Abbott

You may also like

The Secret to Getting Young Urbanites Outdoors? ‘Mappiness’

March 23, 2023

Find Snow-Free Trails with the Snow Depth Map

March 9, 2023

How to Read Topographic Maps

February 24, 2023

Book Campsites Right From Gaia GPS

February 23, 2023

Why NatGeo Trails Illustrated are America’s Favorite Maps

February 9, 2023

How to Save Phone Battery Life in the...

February 8, 2023

How to Plan a Backcountry Ski Tour with...

January 26, 2023

Cook Marco Hernandez’s Mouthwatering Camp Meals

January 25, 2023

New! Find Backcountry Skiing in Gaia Winter Map

January 11, 2023

How to Get Started Overlanding

January 9, 2023

Keep in touch

Facebook Twitter Instagram Youtube

Popular Posts

  • 1

    How to Read Topographic Maps

    February 24, 2023
  • 2

    How to Save Phone Battery Life in the Backcountry

    February 8, 2023
  • 3

    How to Download an Entire State Map with Gaia Topo

    August 19, 2021
  • 4

    Using Gaia GPS to Find Free Camping in National Forests

    March 9, 2022
  • 5

    Unlock Adventure with Gaia GPS on Outside+

    September 30, 2021

Categories

  • Adventures
  • Android
  • App Comparisons
  • App Updates
  • Backcountry Skiing
  • Boating
  • Company News
  • Emergency Response
  • Featured
  • Fishing
  • Gaia GPS
  • Gaia GPS Offroad Podcast
  • GaiaCloud
  • Hikes
  • How-To
  • Hunting
  • iOS
  • New Features
  • New Maps
  • Newsletter
  • Offroading
  • Out and Back Podcast
  • User Profiles
  • Facebook
  • Twitter
  • Instagram
  • Youtube
  • RSS

@2022 - All Right Reserved. Gaia GPS


Back To Top