What is the function of icons at the top of maps?
Most of the icons enable the user to zoom in or out. As the zoom level changes, so do labels and geophysical or historical background. At the far left are pointers to the left and right. Once one begins to move back and forth between zoom levels by icons to the right, these pointers provide an alternative means of changing zoom level. Next, from left to right, are icons of a hand and an empty magnifying glass. As explained on p. 20 of the Guide, these icons allow you to zoom in a map by defining an area to enlarge: (1) click on the empty magnifying glass icon; (2) using the cross-hair cursor, click and hold the mouse button and then drag the mouse diagonally over the area you wish to enlarge; and (3) release the mouse button. The middle icons also allow you to zoom in (+) or zoom out (-) between 4 levels or scales: 20, 6, 3, and 1, as shown at the bottom left of the map. Scale 20 shows the largest area, but the least detail. Only broad regions are labeled at this zoom level. Scales 6 a
