Map Scale

Scale is the relationship that the depicted feature on map has to its actual size in the real world. A map scale usually is given as a fraction or a ratio (e.g. 1/10,000 or 1:10,000). This means that 1 centimeter on the map is equal to 10,000 centimeters on the ground. The unit is interchangeable – 1 meter to 10,000 meters, 1 foot to 10,000 feet, and so on. The larger the second number is (10,000 in this case), the smaller the scale of the map. “The larger the number, the smaller the scale.” (Map Scales, USGS Earth Science Information Center)

As thoughtful map consumers and potential map makers, scale is important to understand as it affects feature representation.

The larger the scale of the map, the better the features that can be detailed. A map that shows the water network of a small area may show the river as a polygon layer and will show the tributaries of that river. A small scale map covering the area would show that same river as a line feature and the tributaries would be removed (a process known as generalization). The smaller the scale of the map, the less the actual detail of a feature is preserved. Smaller scale maps have river features that have the lines smoothed out whereas a large scale map would show more detail about the twists and turns of that same river.

Caitlin Dempsy, September 1, 2011, understanding map scale

To explore an example of small scale versus large scale representation see the GIS Lounge article, Understanding Map Scale, quoted above. Web maps you explore in this lesson and on your own will often provide higher scale maps with more detailed information when zoomed in, and lower scale maps with generalized features as you zoom out.

>> 3) Thematic Maps