A short, friendly guide to basic principles of thematic mapping.
https://www.axismaps.com/guide/
This brief overview of basic thematic mapping is adapted from documentation for indiemapper written in 2010 by Axis Maps. It has been edited to remove software-specific content, to add a bit more information here and there, and to update some links. We hope that with further contributions it can expand to include more helpful information and references.