GTM come at a variety of scales. The GTM 15 Series is a consistent scale of 1:69500 producing uniform 100% coverage of the Washington Cascades and Olympics as well as Oregons Northern Cascades. GTM S (Special) Maps vary in scale, typically a larger scale (more detail) than the 15 series.

The scale of the map is determined by the amount of real-world area covered. For example, a 15 GTM topographic map has a scale of 1:69500. This type of scale is known as a Ratio Scale meaning one inch(one of anything- km, cm, foot etc) on the map is equal to 69,500 inches(km, cm, foot etc)in the real world. The smaller the ratio is between distances on the map and distances in the real world, the smaller the scale of the map is said to be.

A map with a scale of 1:69,500 is a smaller scale map than a 1:24,000 scale S map, but it covers a larger real-world area. In addition to the ratio scale, a bar scale is also shown to allow measurement of distances on the map and conversion to real-world distances.

Perhaps one of the most important sources of information on a Green Trails Map is the date of revision, typically printed in the legend box. Although large scale topographic features, such as mountains, take millions of years to be formed and eroded, smaller scale features change on a much more rapid scale. For example, the path of a trail may change fairly rapidly as a result of flooding, landslides that may alter topography significantly, roads and trails are added or go out of use, etc.  Because of these changes, it is important to have a the most recently updated GTM to ensure accurate and current recreation content.


Updating Your Backpack