32:[{"id":"44e844e68240a35718846eaa5c217d541e4b6bb7245848fe5d6bb90c2cd759a804f3c56dbf681049dd53b6cb26d9911f18210beb1859ea5307fb3e087141a576","href":"https://static.observableusercontent.com/files/44e844e68240a35718846eaa5c217d541e4b6bb7245848fe5d6bb90c2cd759a804f3c56dbf681049dd53b6cb26d9911f18210beb1859ea5307fb3e087141a576","name":"world-50m.json","type":"application/json","lastModified":1655933715638.978,"size":744301},{"id":"5667cf6ea53cdbed31600d60556314bcefb28a3bbd66abb351464ab8cf0665cc3a4d508f73841f6ffa78ec215f8ee8acf29e09b8429409b30a3c7e4a18cc2f7f","href":"https://static.observableusercontent.com/files/5667cf6ea53cdbed31600d60556314bcefb28a3bbd66abb351464ab8cf0665cc3a4d508f73841f6ffa78ec215f8ee8acf29e09b8429409b30a3c7e4a18cc2f7f","name":"world-110m_withlakes.topo.json","type":"application/json","lastModified":1655933575264.184,"size":92469},{"id":"be41daaf188cea412654faf070d59c21f684d937ed804388709425dca8e6c79a0981bfa9202b3ae6ff65fc2b9ebc7ac310f00d17299a310b8354a68129f41dd3","href":"https://static.observableusercontent.com/files/be41daaf188cea412654faf070d59c21f684d937ed804388709425dca8e6c79a0981bfa9202b3ae6ff65fc2b9ebc7ac310f00d17299a310b8354a68129f41dd3","name":"great_circle.topo.json","type":"application/json","lastModified":1655938936043.284,"size":521575}] 30:{"title":"Peirce quincuncial projection and great-circle path","cells":[{"id":0,"value":"# Peirce quincuncial projection and great-circle path","pinned":false,"hidden":false,"mode":"md"},{"id":300,"value":"

\n The Peirce Quincuncial projection map has the interesting property that it can be tiled infinitely on the plane. \n

\n The following map shows examples of shortest distances for the travels (as the crow flies) between the following cities: Geneva, Seattle, Valparaiso, Rio de Janeiro, Madagascar, Tokyo, Shangai, Sydney.\n

\n Check the following links for inspiration and for calculations:\n

Mike Bostock’s notebook on Peirce's quincuncial projection: [@d3/peirce-quincuncial]
Great circle and shortest distance: great-circle distance

\n Check also this dynamic version of the Peirce quincuncial projection.\n

\n
","pinned":false,"hidden":false,"mode":"html"},{"id":320,"value":"{\n const context = DOM.context2d(width, height);\n context.translate(width / 2, height / 2);\n context.scale(0.5, 0.5);\n context.globalAlpha = map_transparency;\n context.drawImage(map, 0, 0, width, height);\n context.globalAlpha = 1; \n context.drawImage(map, -width, -width, width, height);\n context.rotate(Math.PI);\n context.globalAlpha = map_transparency; \n context.drawImage(map, -width, 0, width, height);\n context.drawImage(map, 0, -width, width, height);\n \n return context.canvas;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":14,"value":"md`---\n\n## Appendix`","pinned":false,"hidden":false,"mode":"ojs"},{"id":170,"value":"height = 1150;\n","pinned":false,"hidden":false,"mode":"ojs"},{"id":179,"value":"width = height;","pinned":false,"hidden":false,"mode":"ojs"},{"id":352,"value":"map_transparency = 0.3","pinned":false,"hidden":false,"mode":"ojs"},{"id":185,"value":"color_lakes = '#0ac'","pinned":false,"hidden":false,"mode":"ojs"},{"id":239,"value":"color_land = \"#666\"","pinned":false,"hidden":false,"mode":"ojs"},{"id":252,"value":"color_boundaries = \"#999\"","pinned":false,"hidden":false,"mode":"ojs"},{"id":272,"value":"color_routes = \"#e04\"","pinned":false,"hidden":false,"mode":"ojs"},{"id":18,"value":"// We don't display this map\nmap = {\n const context = DOM.context2d(width, height);\n const projection = d3.geoPeirceQuincuncial().fitSize([width, height], {type: \"Sphere\"}).precision(0.1);\n const path = d3.geoPath(projection, context);\n path.pointRadius(0.8);\n \n context.beginPath(), path(graticule), context.strokeStyle = \"#ddd\", context.stroke();\n context.beginPath(), path(land), context.fillStyle = color_land, context.fill();\n context.beginPath(), path(countries), context.strokeStyle = color_boundaries, context.stroke();\n context.beginPath(), path(add_lakes), context.fillStyle = color_lakes, context.fill();\n context.beginPath(), path(routes), context.strokeStyle = color_routes, context.point= \"1\", context.stroke();\n\t\n context.canvas.style.display=\"none\"; \n return context.canvas;\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":7,"value":"d3 = require(\"d3@5\", \"d3-geo@1\", \"d3-geo-projection@2\")","pinned":true,"hidden":false,"mode":"ojs"},{"id":29,"value":"graticule = d3.geoGraticule10()","pinned":true,"hidden":false,"mode":"ojs"},{"id":31,"value":"world = FileAttachment(\"world-50m.json\").json()","pinned":true,"hidden":false,"mode":"ojs"},{"id":43,"value":"land = topojson.feature(world, world.objects.land)","pinned":true,"hidden":false,"mode":"ojs"},{"id":249,"value":"countries = topojson.feature(world, world.objects.countries)","pinned":true,"hidden":false,"mode":"ojs"},{"id":46,"value":"lakes = FileAttachment(\"world-110m_withlakes.topo.json\").json()","pinned":true,"hidden":false,"mode":"ojs"},{"id":48,"value":"add_lakes = topojson.feature(lakes, lakes.objects.lakes)","pinned":true,"hidden":false,"mode":"ojs"},{"id":267,"value":"routes = FileAttachment(\"great_circle.topo.json\").json()","pinned":true,"hidden":false,"mode":"ojs"}],"files":"$W32","stdlib":"1","titling":"auto"}