The file tobler-approximation.txt contains an approximation of the Tobler hyperelliptical world map projection
which can be loaded and edited in Flex Projector.
<http://flexprojector.com/>

The approximation was generated by Tobias Jung for <http://map-projections.net/> and is in the public domain.
It's not perfect, so you're welcome to improve it.

NOTE:
When open the file in Flex Projector, you'll notice that the Distortion Table shows a wighted mean error
of 0.11 in the Areal Distortion column, whereas an equal-area projection should have 0.
To fix this, use the "Projection Size" option in Flex Projector and select "Minimize Area Distortion".
Since it is recommended to adjust the projection size at the end of the design process and you might
want to apply some changes to the approximation, I refrained from using this option before saving the file.

