Topographic Map Basics
First of all, Topo is short for topographic if you didn’t already know that. Topography is the detailed mapping of surface features such as mountains, depressions, rivers, lakes, as well as constructed features be it a dam, railroad, forest service road, or trail. Contour lines are a prominent feature on this type of map that enables a person to accurately identify their surroundings and orientation by identifying terrain features. Contour lines connect points on a map that are at the same elevation.
So the contour lines of something like a steep mountain ridge would be close together. Although they are stacked together on the GPS map two dimensionally it helps to look at them as if they were three dimensional and grew up from the map as the elevation of the land it represents grew to its pinnacle. I’m sure that kind of technology will be here before we know it anyway. The distance between vertically spaced contour lines is different on some maps therefore you must check the legend to see if they’re 20 or 80 feet, for example. The contour spacing for an individual maps, however, is always constant. The hillier, mountainous terrain will have a greater distance between lines to prevent the map from being overcrowded with lines.
In the United States, a government agency known as the U.S. Geological Survey began a comprehensive mapping of the U.S. in 1979. The preeminent USGS maps are 1:24,000-scale topographic maps, also known as 7.5-minute quadrangles. They finished their work in 1992 and many of the digitized maps found on GPS screens are related to their efforts. Garmin GPS maps are typically on a 1:100,000 scale.
Incidentally, if you’re in the market and searching for the best Garmin for a given outdoor activity, click on the link for each of the following; Geocaching, backpacking, fishing, and hunting.