PNG -> GeoTIFF conversion for Blue Marble PNGs

convert.rb

def trans_lat(lat)
  lat =~ /([0-9]+)([NS])/

  num, dir = $1.to_i, $2

  dir == 'S' ? -num : num
end

def trans_long(long)
  long =~ /([0-9]+)([EW])/

  num, dir = $1.to_i, $2

  dir == 'W' ? -num : num
end

data = if ARGV.length > 0
  ARGV.map { |f| File.read(f) }.join("\n")
else
  $stdin.read
end

data.split("\n").each do |row|
  fn, ul_lat, ul_long, lr_lat, lr_long, res = row.split("\t")

  dst = fn.sub(File.extname(fn), '.tiff')

  uly = trans_lat(ul_lat)
  ulx = trans_long(ul_long)
  lry = trans_lat(lr_lat)
  lrx = trans_long(lr_long) 

  cmd = "gdal_translate -a_srs WGS84 -a_ullr #{ulx} #{uly} #{lrx} #{lry} #{fn} /gtiff/output/#{dst}"
  puts cmd
  `#{cmd}`
end

manifest

world.topo.200408.3x21600x21600.A1.png	90N	180W	0N	90W	240
world.topo.200408.3x21600x21600.A2.png	0N	180W	90S	90W	240
world.topo.200408.3x21600x21600.B1.png	90N	90W	0N	0W	240
world.topo.200408.3x21600x21600.B2.png	0N	90W	90S	0W	240
world.topo.200408.3x21600x21600.C1.png	90N	0W	0N	90E	240
world.topo.200408.3x21600x21600.C2.png	0N	0W	90S	90E	240
world.topo.200408.3x21600x21600.D1.png	90N	90E	0N	180E	240
world.topo.200408.3x21600x21600.D2.png	0N	90E	90S	180E	240

More info and source data:

http://visibleearth.nasa.gov/view.php?id=73776
http://eoimages.gsfc.nasa.gov/images/imagerecords/73000/73776/readme.pdf (extent data)