Icon Meaning Topic objectives. The objectives are highlighted to help keep the goals of the topic in focus. Basic introduction to a topic. In depth information on how to apply basic knowledge in a modeling context. Advanced information that provides improved approaches and understanding, but may have limited application to field problems because of lack of data or other resources.
Advanced topics are optional and provided mostly for enrichment.
Major ideas are indicated by the light bulb icon. The calculator indicates upcoming usage of an OnSite calculator. The envelope indicates a back of the envelope calculation. Sometimes what's produced on the back of an envelope is brilliant. Lincoln's Gettysburg Address is reported to be an example.