Map with d3.js and TopoJSON, Albers Siberia projection -


i'm trying make choropleth d3.js got stucked @ beginning. found shapefile , generated geojson , topojson files here. map uses albers-siberia projection. found projection:

projection: albers equal-area conic

  • units: meters
  • spheroid: krasovsky
  • central meridian: 105
  • standard parallel 1: 52
  • standard parallel 2: 64
  • reference latitude: 0
  • false easting: 18500000
  • false northing: 0

proj.4: +proj=aea +lat_1=52 +lat_2=64 +lat_0=0 +lon_0=105 +x_0=18500000 +y_0=0 +ellps=krass +units=m +towgs84=28,-130,-95,0,0,0,0 +no_defs

mapinfo: "albers-siberia", 9, 1001, 7, 105, 0, 64, 52, 18500000, 0.

so got code , make nothing (and freez up), what's wrong?

<!doctype html> <html lang="en"> <head>     <meta charset="utf-8">     <title>choropleth</title>     <script type="text/javascript" src="d3/d3.v3.js"></script>     <script type="text/javascript" src="d3/queue.v1.min.js"></script>     <script type="text/javascript" src="d3/topojson.v0.min.js"></script> </head> <body>     <h1>my choropleth</h1>     <script type="text/javascript">          var width = 960,             height = 500;          var svg = d3.select("body").append("svg")                     .attr("width", width)                     .attr("height", height);          var pr = d3.geo.albers()             .center([105,0])             .parallels([52, 64])             .scale(1000);           var path = d3.geo.path().projection(pr);          d3.json("map_rus_topo.json", function(error, map) {          svg.append("path")           .datum(topojson.object(map, map.objects.map_rus))           .attr("d", path);         });      </script> </body>

can find json files here.
, 1 more question: how can reference value of region field in my topojson file.

the first problem geojson file isn’t in degrees [longitude°, latitude°], otherwise known epsg:4326 or wgs 84. convert geojson file wgs 84, first need create projection file, albers.prj can tell ogr source projection is.

+proj=aea +lat_1=52 +lat_2=64 +lat_0=0 +lon_0=105 +x_0=18500000 +y_0=0 +ellps=krass +units=m +towgs84=28,-130,-95,0,0,0,0 +no_defs

then, “unproject” geojson file converting wgs 84:

ogr2ogr -f geojson -s_srs albers.prj -t_srs epsg:4326 map_rus_wgs84_geo.json map_rus_geo.json

now can convert topojson in wgs 84, rather projected coordinates. i’ve taken liberty of doing simplification:

topojson -o map_rus_wgs84_topo.json -s 1e-7 -- russia=map_rus_wgs84_geo.json

the second problem projection definition in d3 incorrect. d3.geo.albers projection has default rotate , center that’s designed u.s.-centered map, in addition defining center you’ll need override default rotation. in fact, +lon_0 (central meridian) projection parameter maps projection’s rotation, not projection’s center. giving:

var projection = d3.geo.albers()     .rotate([-105, 0])     .center([-10, 65])     .parallels([52, 64])     .scale(700)     .translate([width / 2, height / 2]);

(i fudged center parameter put russia @ center of viewport. can compute automatically if prefer.) should see this:

albers siberia

it’s possible work projected (cartesian) coordinates in topojson, , define d3.geo.path null (identity) projection, i’ll leave separate question.


Comments

Post a Comment

Popular posts from this blog

Why does Ruby on Rails generate add a blank line to the end of a file? -

running rails generate controller foo home results in: class foocontroller < application controller def home end end (there's nothing on line in actual file, blank line) is there purpose blank line? it's common use newline indicate end of line, last line. many editors (like vi, use) add in newline silently. consensus text files (especially in unix world) should end in newline, , there have been problems historically if wasn't present. why should text files end newline? the tool used count lines in file "wc" counts newlines in file, without trailing newline show 3 instead of 4. it improves readability of templates used in generator. consider: https://github.com/rails/rails/blob/master/railties/lib/rails/generators/rails/controller/templates/controller.rb to remove trailing newline, template have last line of: end<% end -%> instead of: end <% end -%> that seems less readable me. the discussion below refers
Read more

keyboard - Smiles and long press feature in Android -

i've created android keyboard. how add features inserting smilies, , using long keypresses display symbols? to create long-press behavior allows select several options pop-up menu, follow guide (specifically pop-up menu section): http://developer.android.com/guide/topics/ui/menus.html smileys (also known emoticons) combination of keys, understood programs , parsed same way. have do, when clicks smiley face on keyboard, simulate pressing of key combination matching emoticon. example, when clicks smiley, should simulate key presses ':' , ')' :). here's list of emoticons: http://en.wikipedia.org/wiki/list_of_emoticons
Read more

node.js - Bad Request - node js ajax post -

i'm using express 3.0 , node v0.11.0. have button submits form , i'm using ajax post data json object node server. client code is: $('#contact').submit(function(e) { console.log('submit called'); var formdata = json.stringify($('form').serializeobject()); console.log(formdata); $.ajax({ url: "http://localhost:3000/savedata/", type: "post", datatype: 'json', data: {objectdata: formdata}, contenttype: "application/json", complete: function() { console.log('process complete'); }, success: function(data) { console.log('process sucess'); }, error: function() { console.log('process error'); }, }); return false; }); then on server: var express = require('express'); var app = express(); app.set('views', __dirname + '/views'); app.set('view engine', 'jade'); app.use(express.bodyparser());
Read more