{"id":1834237,"date":"2024-09-24T21:24:00","date_gmt":"2024-09-25T01:24:00","guid":{"rendered":"https:\/\/www.maproomblog.com\/?p=1834237"},"modified":"2024-09-24T21:24:02","modified_gmt":"2024-09-25T01:24:02","slug":"chinas-gps-shift-and-online-maps","status":"publish","type":"post","link":"https:\/\/www.maproomblog.com\/2024\/09\/chinas-gps-shift-and-online-maps\/","title":{"rendered":"China\u2019s GPS Shift and Online Maps"},"content":{"rendered":"\n<p>If the road grid in online maps of China doesn\u2019t line up with the aerial\/satellite imagery layer, <a href=\"https:\/\/medium.com\/@anastasia.bizyayeva\/every-map-of-china-is-wrong-bc2bce145db2\">Anastasia Bizyayeva explains in a Medium post earlier this year<\/a>, it\u2019s because China\u2019s map data uses a different geodetic datum, <a href=\"https:\/\/en.wikipedia.org\/wiki\/Restrictions_on_geographic_data_in_China#GCJ-02\">GCJ-02<\/a>, rather than WGS-84. \u201cGCJ-02 is based on WGS-84, but with a\u00a0deliberate obfuscation algorithm\u00a0applied to it. The effect of this is that there are random offsets added to both latitude and longitude, ranging from as little as 50m to as much as 500m.\u201d Chinese map companies are obliged to use GCJ-02 so their maps and imagery line up; outside China, companies can choose to use Chinese data <em>and <\/em>imagery and have alignment artifacts at the Chinese border, or use Chinese data with images aligned with WGS-84 and have the roads appear offset from the imagery. [<a href=\"https:\/\/kottke.org\/24\/09\/0045314-online-street-maps-and-sa\">Kottke<\/a>]<\/p>\n","protected":false},"excerpt":{"rendered":"<p>If the road grid in online maps of China doesn\u2019t line up with the aerial\/satellite imagery layer, Anastasia Bizyayeva explains in a Medium post earlier this year, it\u2019s because China\u2019s map data uses a different&hellip; <a href=\"https:\/\/www.maproomblog.com\/2024\/09\/chinas-gps-shift-and-online-maps\/\">More<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"link","meta":{"autoblue_enabled":true,"autoblue_custom_message":"","autoblue_shares":[],"autoblue_post_url":"","_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[490],"tags":[182,593,1693,177],"class_list":["post-1834237","post","type-post","status-publish","format-link","hentry","category-censorship","tag-china","tag-datum","tag-gcj-02","tag-satellite-imagery","post_format-post-format-link"],"jetpack_featured_media_url":"","jetpack-related-posts":[{"id":479,"url":"https:\/\/www.maproomblog.com\/2016\/01\/online-map-updates\/","url_meta":{"origin":1834237,"position":0},"title":"Online Map Updates","author":"Jonathan Crowe","date":"22 January 2016","format":"link","excerpt":"Yesterday's\u00a0updates to Apple Maps include four new Flyover cities, traffic data for Hong Kong and Mexico, public transit data for Los Angeles, and Nearby search for the Netherlands. Google Earth Blog reports on the mid-January imagery update for Google Earth. Google Earth Blog also reports that\u00a0version 1.0 of ArcGIS Earth\u2026","rel":"","context":"In &quot;GIS&quot;","block_context":{"text":"GIS","link":"https:\/\/www.maproomblog.com\/category\/gis\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":1789197,"url":"https:\/\/www.maproomblog.com\/2020\/08\/blank-map-tiles-point-to-locations-of-xinjiang-detention-centres\/","url_meta":{"origin":1834237,"position":1},"title":"Blank Map Tiles Point to Locations of Xinjiang Detention Centres","author":"Jonathan Crowe","date":"31 August 2020","format":"link","excerpt":"As part of their investigation into China\u2019s practice of detaining Uighur and other Muslim minorities in Xinjiang, Buzzfeed News journalists compared blanked-out areas in Baidu Maps with uncensored imagery from Google Earth and satellite data providers, and, after sorting through some 50,000 possible locations using custom web tools, built a\u2026","rel":"","context":"In &quot;Censorship&quot;","block_context":{"text":"Censorship","link":"https:\/\/www.maproomblog.com\/category\/censorship\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":5390,"url":"https:\/\/www.maproomblog.com\/2012\/09\/ios-6-maps-first-impressions\/","url_meta":{"origin":1834237,"position":2},"title":"iOS 6 Maps: First Impressions and More Links","author":"Jonathan Crowe","date":"23 September 2012","format":"link","excerpt":"I've been poking around with iOS 6 maps on both my fourth-generation iPod touch and on Jennifer's third-generation iPad. My initial impression is that the app is fast and renders streets quickly, and turn-by-turn directions seem to be okay in practice. The satellite imagery comes from different sources than Google's\u2026","rel":"","context":"In &quot;Mobile&quot;","block_context":{"text":"Mobile","link":"https:\/\/www.maproomblog.com\/category\/mobile\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":1814191,"url":"https:\/\/www.maproomblog.com\/2023\/04\/updated-satellite-imagery-of-ukraine-reveals-russian-fortifications-damage\/","url_meta":{"origin":1834237,"position":3},"title":"Updated Satellite Imagery of Ukraine Reveals Russian Fortifications, Damage","author":"Jonathan Crowe","date":"27 April 2023","format":"link","excerpt":"Recent satellite imagery reveals the extent of Russian defensive fortifications built in the past few months in occupied territory in anticipation of Ukraine\u2019s spring counteroffensive: see coverage from CNN and Reuters. Meanwhile, Maps Mania reports that Google Maps\u2019 updated satellite imagery of Ukraine shows the damage inflicted by the Russian\u2026","rel":"","context":"In &quot;Conflicts&quot;","block_context":{"text":"Conflicts","link":"https:\/\/www.maproomblog.com\/category\/conflicts\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":5222,"url":"https:\/\/www.maproomblog.com\/2017\/10\/mapping-the-northern-california-wildfires\/","url_meta":{"origin":1834237,"position":4},"title":"Mapping the Northern California Wildfires","author":"Jonathan Crowe","date":"17 October 2017","format":"link","excerpt":"Maps and satellite imagery of the wildfires in Northern California include the San Francisco Chronicle\u2019s interactive map; Robin Kraft's interactive map \u00a0showing satellite imagery from before and after the fire; this New York Times page mapping building damage in Santa Rosa; the\u00a0Washington Post\u2019s coverage of the devastation; and NASA Earth\u2026","rel":"","context":"In &quot;Disasters&quot;","block_context":{"text":"Disasters","link":"https:\/\/www.maproomblog.com\/category\/disasters\/"},"img":{"alt_text":"NASA Earth Observatory","src":"https:\/\/i0.wp.com\/www.maproomblog.com\/xq\/wp-content\/uploads\/2017\/10\/nasa-norcal-wildfires-1024x546.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.maproomblog.com\/xq\/wp-content\/uploads\/2017\/10\/nasa-norcal-wildfires-1024x546.jpg?resize=350%2C200 1x, https:\/\/i0.wp.com\/www.maproomblog.com\/xq\/wp-content\/uploads\/2017\/10\/nasa-norcal-wildfires-1024x546.jpg?resize=525%2C300 1.5x, https:\/\/i0.wp.com\/www.maproomblog.com\/xq\/wp-content\/uploads\/2017\/10\/nasa-norcal-wildfires-1024x546.jpg?resize=700%2C400 2x"},"classes":[]},{"id":4681,"url":"https:\/\/www.maproomblog.com\/2017\/08\/esri-makes-satellite-imagery-available-to-openstreetmap-editors\/","url_meta":{"origin":1834237,"position":5},"title":"Esri Makes Satellite Imagery Available to OpenStreetMap Editors","author":"Jonathan Crowe","date":"27 August 2017","format":"link","excerpt":"Esri is making its satellite imagery collection available to OpenStreetMap editors. Today Esri is proud to announce that we are making our own global collection of satellite imagery available to the OSM community directly through our existing\u00a0World Imagery Service. This regularly updated resource provides one meter or better satellite and\u2026","rel":"","context":"In &quot;Industry&quot;","block_context":{"text":"Industry","link":"https:\/\/www.maproomblog.com\/category\/industry\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]}],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.maproomblog.com\/wp-json\/wp\/v2\/posts\/1834237","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.maproomblog.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.maproomblog.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.maproomblog.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.maproomblog.com\/wp-json\/wp\/v2\/comments?post=1834237"}],"version-history":[{"count":6,"href":"https:\/\/www.maproomblog.com\/wp-json\/wp\/v2\/posts\/1834237\/revisions"}],"predecessor-version":[{"id":1834247,"href":"https:\/\/www.maproomblog.com\/wp-json\/wp\/v2\/posts\/1834237\/revisions\/1834247"}],"wp:attachment":[{"href":"https:\/\/www.maproomblog.com\/wp-json\/wp\/v2\/media?parent=1834237"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.maproomblog.com\/wp-json\/wp\/v2\/categories?post=1834237"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.maproomblog.com\/wp-json\/wp\/v2\/tags?post=1834237"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}