Plots GPX files, see http://suffix.be/blog/rendering-gpx-gps-log-ruby

gpx2image

#!/usr/bin/env ruby
require 'rubygems'
require 'nokogiri'
require 'gnuplot'

if ARGV[0]
  source = ARGV[0]
else
  puts "usage: ./gpx2image source_file"
  exit(0)
end
doc = Nokogiri::XML(open(source))

minlat = (doc.xpath('/xmlns:gpx/xmlns:bounds/@minlat').to_s.to_f * 100).round.to_f / 100
maxlat = (doc.xpath('/xmlns:gpx/xmlns:bounds/@maxlat').to_s.to_f * 100).round.to_f / 100
minlon = (doc.xpath('/xmlns:gpx/xmlns:bounds/@minlon').to_s.to_f * 100).round.to_f / 100
maxlon = (doc.xpath('/xmlns:gpx/xmlns:bounds/@maxlon').to_s.to_f * 100).round.to_f / 100

# TODO Negative coordinates
latdiff = maxlat - minlat
londiff = maxlon - minlon
latmid = (minlat + maxlat) / 2
lonmid = (minlon + maxlon) / 2

if latdiff > londiff # portrait
  minlon = lonmid - (latdiff / 2)
  maxlon = lonmid + (latdiff / 2)
  minlat = latmid - (latdiff / 2)
  maxlat = latmid + (latdiff / 2)
else # landscape
  minlat = latmid - (londiff / 2)
  maxlat = latmid + (londiff / 2)
  minlon = lonmid - (londiff / 2)
  maxlon = lonmid + (londiff / 2)
end

x = doc.xpath('//xmlns:trkpt/@lon').map{|pt| pt.to_s.to_f}
y = doc.xpath('//xmlns:trkpt/@lat').map{|pt| pt.to_s.to_f}

Gnuplot.open do |gp|
  Gnuplot::Plot.new(gp) do |plot|
    # plot.arbitrary_lines << 'set terminal "png"'
    # plot.arbitrary_lines << 'set output "some.png"'
    # plot.arbitrary_lines << "unset border"
    plot.arbitrary_lines << "set grid"
    # plot.arbitrary_lines << "unset tics"
    plot.arbitrary_lines << "set size square"
    plot.arbitrary_lines << "set yrange [#{minlat}:#{maxlat}]"
    plot.arbitrary_lines << "set xrange [#{minlon}:#{maxlon}]"
    # plot.arbitrary_lines << 'set term svg'
    plot.data << Gnuplot::DataSet.new([x, y]) do |ds|
      ds.with = "lines"
      ds.notitle
    end
  end
end

exit(0)