A topographic map is a two-dimensional illustration of the three-dimensional floor of the land. A topographic map allows you to visualize the hills and valleys of the land itself. It additionally gives particular particulars as to the elevation of the floor. Topography is the form of the land floor. Topographic map contour strains signify the land floor.
Contour Strains
Strains snake their manner round a topographic map. They’re known as contour strains.
All factors alongside the identical contour line are on the similar elevation above sea degree.
Consider a contour line as a closed loop. By following one, you’d journey flat, not uphill or downhill, and would finally find yourself again round at your place to begin when you went all the best way round it. They’re used to find out elevations (referred to in toes or meters, above sea degree).
Topographic contour strains assist you to work out basic terrain traits from their patterns. For instance, strains which can be crowded shut collectively – signifies that the terrain is steep. Strains spaced extensively aside point out extra mild slopes.
Additionally they development up valleys and type a “V” or a “U” the place they cross a stream.
Thick and Skinny
You’ll discover each skinny and thick contour strains on a topographic map. “Index strains” are thick. “Interval strains” are skinny. They each signify contour elevation.
Index Strains
Nevertheless, index strains (the daring / thick strains) are usually labeled with a quantity indicating the elevation for that individual line.
Interval Strains and Contour Interval
The skinny interval strains are unmarked.
The space represented between every of the interval strains is named the contour interval. The contour interval is said on each topographic map and is often positioned close to the size.
For instance, if a topographic map scale signifies a contour interval of 6 meters (practically 20 toes), and a selected thick ‘index’ contour line on the map is labeled ‘1040’, which means all the pieces alongside that contour line is at 1040 meters elevation above sea degree (the newer USGS topo maps are in meters), and every skinny line above or under that index line is a distinction of 6 meters.
Word: A thought to keep in mind when you’re utilizing a map out on the bottom… The hole between the interval strains – 6m – if a function on the land is smaller than that top, and located between two elevation intervals, it could not seem on the map in any respect. So, concentrate on that distance, relying on the map you’re studying.
Topographical Map Contour Strains Visualize The Land
The fantastic thing about a topographic map is its skill to deduce an image in your thoughts of the lay of the land. When you enable your eyes to watch the general sample of the thick and skinny contour strains, it turns into pretty straightforward to think about the hills and valleys.
The topo map might assist you to find the place you might be. For instance, if you realize that you’re inside the confines of a given map, you might doubtlessly go searching and determine a number of (3 is sweet) factors akin to hilltops, valleys, and so forth. after which take a look at your map with that body of reference in your thoughts whereas looking for a similar identifiers on the contour of the map itself. By utilizing triangulation you might uncover your present place on the map.
The distinctive “V” or “U” shapes alongside strains of contour will point out the place rivers and streams will probably be (which themselves are usually drawn on the map in blue).
In fact it might assist to have a superb compass!
Right here’s a high quality basic, Made within the USA. I’ve had this one for a lot of, a few years. The tritium nonetheless places out gentle…
Tritium Lensatic Compass
(view on amzn)
There are numerous makes use of for topographic maps. It might be a good suggestion to have a number of which cowl the geography of the land close to the place you reside, or different areas of curiosity the place it’s possible you’ll journey.
The USGS website, store.usgs.gov is a pleasant useful resource the place you possibly can choose a location for accessible map choices. You may obtain them as a PDF without spending a dime. You can too buy onerous copies too.
[ Read: Compass For Map Reading And Navigation ]