Inverse Projection
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<!DOCTYPE html> | |
<html lang="en"> | |
<head> | |
<meta charset="utf-8"> | |
<meta http-equiv="X-UA-Compatible" content="IE=edge"> | |
<meta name="viewport" content="width=device-width, initial-scale=1"> | |
<title>Inverse Projection</title> | |
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.6/d3.min.js"></script> | |
<script src="https://cdnjs.cloudflare.com/ajax/libs/topojson/1.6.19/topojson.min.js"></script> | |
</head> | |
<body> | |
<style> | |
body { | |
margin: 0; | |
} | |
svg { | |
background-color: #4B4B55; | |
cursor: crosshair; | |
} | |
.sphere { | |
fill: none; | |
stroke: #d6ff9f; | |
} | |
.coords { | |
stroke: none; | |
fill: #8DBD0C; | |
font-family: 'Helvetica Neue', Helvetica, sans-serif; | |
} | |
.land { | |
fill: #8DBD0C; | |
fill-opacity: 0.25; | |
stroke: #8DBD0C; | |
stroke-width: 1; | |
} | |
</style> | |
<div id="map-container"></div> | |
<script> | |
// Set the dimensions of the map | |
var width = 960, | |
height = 480; | |
// Create a selection for the container div and append the svg element | |
var div = d3.select('#map-container'), | |
svg = div.append('svg'); | |
// Set the size of the SVG element | |
svg.attr('width', width).attr('height', height); | |
// Create a text element to write the coordinates | |
var label = svg.append('text') | |
.classed('coords', true) | |
.attr('x', 20) | |
.attr('y', 30); | |
// Create and configure a geographic projection | |
var projection = d3.geo.equirectangular() | |
.translate([width / 2, height / 2]); | |
// Create and configure a path generator | |
var pathGenerator = d3.geo.path() | |
.projection(projection); | |
// Create and configure the graticule generator (one line every 20 degrees) | |
var graticule = d3.geo.graticule() | |
.step([20, 20]); | |
// Retrieve the geographic data asynchronously | |
d3.json('land.topojson', function(err, data) { | |
// Throw errors on getting or parsing the file | |
if (err) { throw err; } | |
// Convert the TopoJSON features to GeoJSON | |
var features = topojson.feature(data, data.objects.land); | |
// Sphere | |
var sphere = svg.selectAll('path.sphere').data([{type: 'Sphere'}]); | |
sphere.enter().append('path').classed('sphere', true); | |
sphere.attr('d', pathGenerator); | |
sphere.exit().remove(); | |
// Land | |
var land = svg.selectAll('path.land').data([features]); | |
land.enter().append('path').classed('land', true); | |
land.attr('d', pathGenerator); | |
land.exit().remove(); | |
}); | |
// Attach a listener for the mousemove event | |
svg.on('mousemove', function(ev) { | |
// Get the (x, y) position of the mouse (relative to the SVG element) | |
var pos = d3.mouse(svg.node()), | |
px = pos[0], | |
py = pos[1]; | |
// Compute the corresponding geographic coordinates using the inverse projection | |
var coords = projection.invert([px, py]); | |
// Format the coordinates to have at most 4 decimal places | |
var lon = coords[0].toFixed(4), | |
lat = coords[1].toFixed(4); | |
// Set the content of the label | |
label.text([lat, lon].join(', ')); | |
}); | |
</script> | |
</body> | |
</html> |
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# Download and Transform the 1:50m Country Shapefiles from Natural Earth | |
# http://www.naturalearthdata.com/downloads/110m-physical-vectors/ | |
URL = http://www.naturalearthdata.com/http//www.naturalearthdata.com/download/110m/physical/ne_110m_land.zip | |
# Download the zip file from the Natural Earth server | |
ne_110m_land.zip: | |
curl -LO $(URL) | |
# Unzip the shapefiles | |
ne_110m_land.shp: ne_110m_land.zip | |
unzip ne_110m_land.zip | |
touch ne_110m_land.shp | |
# Convert the shapefiles to GeoJSON | |
land.geojson: ne_110m_land.shp | |
ogr2ogr -f GeoJSON land.geojson ne_110m_land.shp | |
# Convert the GeoJSON file to TopoJSON | |
land.topojson: land.geojson | |
topojson -p -o land.topojson land.geojson | |
# Remove source and temporary files | |
clean: | |
rm ne_110m_land* |
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