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Quick Guide To Map Scales
When looking for a map, one of the first questions is "what scale do you need?" The chart below will help you in the decision. Simply defined, scale is the relationship between distance on the map and distance in reality on the ground. The minute series means that the map covers that many degrees in the global system. For example, a 7.5 minute series covers 7.5 minutes of latitude and 7.5 minutes of longitude per sheet.
| Scale | 1 inch equals | 1 centimeter equals |
| 1:20,000 | 1,667 feet | 200 meters |
| 1:24,000 (7.5 minute series) | 2,000 feet | 240 meters |
| 1:25,000 | 2,083 feet | 250 meters |
| 1:50,000 | .8 mile | 500 meters |
| 1:62,500 (15 minute series) | .9 mile | 625 meters |
| 1:63,360 | 1 mile | 634 meters |
| 1:100,000 | 1.6 miles | 1 km |
| 1:250,000 | 4 miles | 2.5 km |
| 1:500,000 (most state maps) | 8 miles | 5 km |
| 1:1,000,000 (~national maps) | 16 miles | 10 km |
Quick Guide To Map Projections
Map projections are attempts to portray the surface of the earth or a portion of the earth on a flat surface. Some distortions of conformality, distance, direction, scale, and area always result
from this process. Some projections minimize distortions in some of these properties at the expense
of maximizing errors in others. Some projection are attempts
to only moderately distort all of these properties. This site describes and
gives visual examples of most forms of projection used:
http://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj_f.html.
