Schuyler Erle > Geo-Dymaxion-0.12 > Geo::Dymaxion

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Module Version: 0.12   Source  

NAME ^

Geo::Dymaxion - Plot latitude/longitude on a Fuller Dymaxion(tm) map

SYNOPSIS ^

  use Geo::Dymaxion;
  
  # Suppose we have a Fuller projection of the Earth's surface that's
  # 800 pixels wide and 600 pixels high.

  my $map = Geo::Dymaxion->new( 800, 600 );

  # Find the x and y coordinates in pixels of Philadelphia, PA, USA.

  my ($x, $y) = $map->plot( 40, -75 );

  # Do the same for Sebastopol, CA, USA.

  ($x, $y) = $map->plot( 38.3993, -122.8259 );

DESCRIPTION ^

Geo::Dymaxion allows you to draw points on Dymaxion(tm) maps using latitude and longitude data, which turns out to be quite difficult and requires some tricky trigonometry. This module strives to hide away all the ugly math and allow you to concentrate on drawing your map.

The Dymaxion(tm), or Fuller, projection was invented by R. Buckminster Fuller in 1954, and is "the only flat map of the entire surface of the Earth which reveals our planet as one island in one ocean, without any visually obvious distortion of the relative shapes and sizes of the land areas, and without splitting any continents." See http://www.bfi.org/map.htm for more details.

METHODS ^

new( [WIDTH [, HEIGHT]] )

new takes two arguments: the length and width of your Dymaxion map in pixels. Be sure when supplying this measure that you have excluded any margins that may exist around the edges of your map image. If no arguments are provided, operations with Geo::Dymaxion will return values expressed in fractions of a unit-sized map.

plot( LATITUDE, LONGITUDE )

plot takes a floating-point (lat, long) pair, and returns a list consisting of floating-point (x, y) coordinates, scaled to the width and height provided to new(). Latitudes south of the equator and longitudes west of the prime meridian should be expressed as negative values. These X and Y values can then be plugged into Imager->setpixel() or any other drawing module you'd care to use.

FUNCTIONS ^

Geo::Dymaxion::dymax( LATITUDE, LONGITUDE )

dymax() provides access to the internal routines used by Geo::Dymaxion. Takes a (lat, long) pair, returns an (x, y) pair, scaled in unit triangle edges, with (0, 0) at the lower left corner of the map. For reference, a Fuller projection of the Earth's surface is 5.5 by sqrt(7.75) unit triangle edges in size.

EXAMPLE ^

  # This script takes a Dymaxion map and (lat, long) point and
  # outputs a JPEG of the map with a large red dot over that point.
  #
  # For a more elaborate example of the same, see:
  #    http://iconocla.st/hacks/dymax/
  
  use Imager;
  use Imager::Fill;
  use Geo::Dymaxion;
  use strict;
  
  my ($lat, $long) = @ARGV;
  my $map_file = "dymaxion.gif"; # make sure the margins are trimmed!

  my $map = Imager->new;
  $map->open( file => $map_file );
  
  my $dymax = Geo::Dymaxion->new( $map->getwidth, $map->getheight );
  my ($x, $y) = $dymax->plot( $lat, $long );
  
  my $dot  = Imager::Color->new( 255, 0, 0 );
  my $fill = Imager::Fill->new( solid => $dot );
  $map->circle( fill => $fill, r => 5, x => $x, y => $y );
  
  $map->write( type => "jpeg", fd => fileno(STDOUT) )
      or die $map->errstr;

BUGS ^

It would be really cool if this module could convert (x, y) points on a Fuller projection back into (lat, long).

DESIDERATA ^

"Think of it. We are blessed with technology that would be indescribable to our forefathers. We have the wherewithal, the know-it-all to feed everybody, clothe everybody, and give every human on Earth a chance. We know now what we could never have known before-that we now have the option for all humanity to "make it" successfully on this planet in this lifetime. Whether it is to be Utopia or Oblivion will b a touch-and-go relay race right up to the final moment." - R. Buckminster Fuller

"When I am working on a problem, I never think about beauty. I only think about how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." - R. Buckminster Fuller

SEE ALSO ^

The word "Dymaxion" and the Fuller projection design are trademarks of the Buckminster Fuller Institute (http://www.bfi.org). The BFI can be reached at <info@bfi.org>.

This module would not exist without the prior work of Robert W. Gray in determining the calculations necessary to plot latitude and longitude on a Fuller map. Gray's notes and original code are available at http://www.rwgrayprojects.com/rbfnotes/maps/graymap1.html, which is well worth the read if you're into such things.

Also, see also Imager, Inline.

AUTHOR ^

Robert W. Gray <rwgray@rwgrayprojects.com> wrote the C code on which this module is based.

Schuyler D. Erle <schuyler@nocat.net> wrote the Perl API, with a little help from Inline.pm.

COPYRIGHT AND LICENSE ^

The C code that performs the actual conversions is copyright Robert W. Gray <rwgray@rwgrayprojects.com>. His code is distributed under the following terms taken from http://www.rwgrayprojects.com/rbfnotes/maps/graymap6.html:

"Usage Note: My work is copyrighted. You may use my work but you may not include my work, or parts of it, in any for-profit project without my consent."

This bears reiteration, in case it wasn't clear the first time: According to Gray's license, you must obtain his consent prior to using his code for commercial or for-profit purposes. Please contact him, not me. (But please contact me if you use this module anyway, I'm curious to know what people might want it for.)

The rest of the module is copyright 2003 by Schuyler D. Erle, and is free software, distributed under the same terms as Perl itself.

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