SVG contours

.gitignore

node_modules
gdalwmscache

elevation.xml

<GDAL_WMS>
  <Service name="TMS">
    <ServerUrl>https://s3.amazonaws.com/elevation-tiles-prod/geotiff/${z}/${x}/${y}.tif</ServerUrl>
  </Service>
  <DataWindow>
    <UpperLeftX>-20037508.34</UpperLeftX>
    <UpperLeftY>20037508.34</UpperLeftY>
    <LowerRightX>20037508.34</LowerRightX>
    <LowerRightY>-20037508.34</LowerRightY>
    <TileLevel>14</TileLevel>
    <TileCountX>1</TileCountX>
    <TileCountY>1</TileCountY>
    <YOrigin>top</YOrigin>
  </DataWindow>
  <Projection>EPSG:3857</Projection>
  <BlockSizeX>512</BlockSizeX>
  <BlockSizeY>512</BlockSizeY>
  <BandsCount>1</BandsCount>
  <DataType>Int16</DataType>
  <ZeroBlockHttpCodes>403,404</ZeroBlockHttpCodes>
  <DataValues>
    <NoData>-32768</NoData>
  </DataValues>
  <Cache/>
</GDAL_WMS>

package-lock.json

{
  "name": "svg-contours",
  "version": "1.0.0",
  "lockfileVersion": 1,
  "requires": true,
  "dependencies": {
    "@mapbox/geo-viewport": {
      "version": "0.2.2",
      "resolved": "https://registry.npmjs.org/@mapbox/geo-viewport/-/geo-viewport-0.2.2.tgz",
      "integrity": "sha1-kyBsBEI4whpg/KfpBkyM5j6AJ7Q=",
      "requires": {
        "@mapbox/sphericalmercator": "1.0.5"
      }
    },
    "@mapbox/sphericalmercator": {
      "version": "1.0.5",
      "resolved": "https://registry.npmjs.org/@mapbox/sphericalmercator/-/sphericalmercator-1.0.5.tgz",
      "integrity": "sha1-cCN7l3QJXtHP286nqP0fyCsmkfI="
    },
    "commander": {
      "version": "2.14.1",
      "resolved": "https://registry.npmjs.org/commander/-/commander-2.14.1.tgz",
      "integrity": "sha512-+YR16o3rK53SmWHU3rEM3tPAh2rwb1yPcQX5irVn7mb0gXbwuCCrnkbV5+PBfETdfg1vui07nM6PCG1zndcjQw=="
    },
    "d3-array": {
      "version": "1.2.1",
      "resolved": "https://registry.npmjs.org/d3-array/-/d3-array-1.2.1.tgz",
      "integrity": "sha512-CyINJQ0SOUHojDdFDH4JEM0552vCR1utGyLHegJHyYH0JyCpSeTPxi4OBqHMA2jJZq4NH782LtaJWBImqI/HBw=="
    },
    "d3-geo": {
      "version": "1.9.1",
      "resolved": "https://registry.npmjs.org/d3-geo/-/d3-geo-1.9.1.tgz",
      "integrity": "sha512-l9wL/cEQkyZQYXw3xbmLsH3eQ5ij+icNfo4r0GrLa5rOCZR/e/3am45IQ0FvQ5uMsv+77zBRunLc9ufTWSQYFA==",
      "requires": {
        "d3-array": "1.2.1"
      }
    },
    "d3-geo-projection": {
      "version": "2.3.2",
      "resolved": "https://registry.npmjs.org/d3-geo-projection/-/d3-geo-projection-2.3.2.tgz",
      "integrity": "sha512-fbIDeSs1n0Y3IxqjtljeHUong4YEK2YS7jR/YKQCoWYBRJLEcieSq1lciCB9+HuNIdJtD7xVRyXFiZGIqu3ydA==",
      "requires": {
        "commander": "2.14.1",
        "d3-array": "1.2.1",
        "d3-geo": "1.9.1"
      }
    },
    "topojson-client": {
      "version": "3.0.0",
      "resolved": "https://registry.npmjs.org/topojson-client/-/topojson-client-3.0.0.tgz",
      "integrity": "sha1-H5kpOnfvQqRI0DKoGqmCtz82DS8=",
      "requires": {
        "commander": "2.14.1"
      }
    }
  }
}

package.json

{
  "name": "svg-contours",
  "version": "1.0.0",
  "description": "",
  "main": "bounds.js",
  "dependencies": {
    "@mapbox/geo-viewport": "^0.2.2",
    "d3-geo-projection": "^2.3.2",
    "topojson-client": "^3.0.0"
  },
  "devDependencies": {},
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC"
}

script.rb

require 'json'

def run_command(command)
  puts command
  system(command) or raise Error
end

lat, lng = "53.868377, -2.300712".split(', ')
zoom     = 12 # Controls the area plotted
scale    = 1  # Finer grained control over area plotted

width    = 1000
height   = width * 0.707

js = <<-JS
var geoViewport = require('@mapbox/geo-viewport');

const bounds = geoViewport.
  bounds([#{lng}, #{lat}], #{zoom}, [#{width*scale},#{height*scale}])

console.log(JSON.stringify(bounds));
JS

node_output           = %x[node -e "#{js}"].chomp
p node_output
left,bottom,right,top = JSON.parse(node_output)

run_command  <<-SH
rm -f pendle.tif
docker run  -v $(pwd):/gdal -w /gdal geographica/gdal2 \
  gdal_translate \
    -of GTiff  \
    -projwin #{left} #{top} #{right} #{bottom} \
    -projwin_srs EPSG:4326 \
    -outsize #{width*5} 0 \
    elevation.xml pendle.tif
SH

run_command  <<-SH
rm -f pendle-4326.tif
docker run  -v $(pwd):/gdal -w /gdal geographica/gdal2 \
  gdalwarp \
    -s_srs EPSG:3857 \
    -t_srs EPSG:4326 \
    pendle.tif pendle-4326.tif
SH

run_command  <<-SH
rm -f contour.geojson
docker run  -v $(pwd):/gdal -w /gdal geographica/gdal2 \
  gdal_contour \
    -a elev pendle-4326.tif \
    -f GeoJSON \
    -i 10.0 \
    contour.geojson
SH

run_command  <<-SH
rm -f contours-simplified.geojson
cat contour.geojson | \
  geoproject 'd3.geoMercator().fitSize([#{width}, #{height}], d)' | \
  geo2topo contours=- | \
  toposimplify -p 1 -f | \
  topoquantize 1e5 | \
  topo2geo contours=contours-simplified.geojson
SH

run_command  <<-SH
rm -f pendle.svg
geo2svg -w #{width} -h #{height} < contours-simplified.geojson > pendle.svg
SH