I think that it would be best to combine the use of a descriptive transcriber's note along with a map. Depending on the grade level and surround text/questions, you can decide what must be included. I suggest that you look through the questions on the Planning Sheet that is posted on the NBA website to determine what is necessary.
In the transcriber's note should explain how you are going to present the graphic. You could list the explorations by countries, and beneath each country list the explorer and dates of travel (in the order they occurred), along with a brief description. (I've inserted maps from the internet on which I based the description, only for your information.) Then show at least the map of Magellan's route.
If you are using a graphics program, you can easily add the various routes to several copies of the same world map. However, if you are creating each of these as masters to thermoform, you may want to limit it to just the map of Megellan's route and a description of the others.
Please see attachment for description based on internet research and what I can identify on your attached map (somewhat fuzzy). I hope this, along with the advice from Katrina, will be useful. Definitely simplify and show only what is essential to the understanding of the text.
I'll send you the attachment in an e-mail as it is too large to post! Sorry.
edited by betty.marshall on 4/1/2010