What Is Contour Interval?
A contour interval may be a perpendicular distance or dissimilarity in altitude between two adjacent contour lines in a topographic map.
Contour Interval on Topographic Map
Index contours are prominent or dense lines that bob up at every 5th isometric line. Generally, there are totally distinct contour intervals for various maps.
For a relief map the contour interval is frequently persistent. For the plotting of region, the contour intervals are presumed. In each plot, the contour intervals are designated on the right-hand side.
If the numbers correlated with definite contour lines are surging, the altitude of the terrain is additionally surging.
A contour is a fictitious line on the bottom attaching the dots having equivalent altitude or a line joining the points of the identical altitude is recognized as an isometric line.
A map or plan representing a 3-dimensional picture of the bottom with the assistance of the contour is termed a map or plan. If you physically followed an isometric line, altitude would persist incessantly.
Contour lines display altitude & additionally the structure of the terrain. Sharp contour points indicate tapered ridges.
How to Find the Contour Interval?
A relief map consists of contour lines of a given geographical area. To sustain the map effortlessly, every isometric line isn’t blotted by its altitude studying. These marked lines are designated as index contour lines.
The evaluation of the contour intervals is as given beneath:
- First, find the 2 index contour lines which might be labeled with a specific loftiness.
- Evaluate the dissimilarity between the 2 selected index contour lines from a map. To take the difference, deduct the upper altitude line with the lower altitude line.
- Now compute the amount of non-index lines contour lines between the 2 indexed contour lines selected for the contour interval computed within the 1st step.
- The range of lines achieved within the above procedure is taken & added with unity.
For instance: if the range of rows between 2 index lines is 5, then add 1 to 5 which turns into 6.
- The ultimate step is that the quotient of the difference between the index lines (step 2) & therefore the type of lines between the 2 index lines added with unity 1 (step 5).
- The ultimate solution is attained by dividing the contour intervals of the actual topographic map.
An Instance of Contour Interval Calculation
Consider, 7000 & 7100; calculate the interval between them.
Difference between 7100 & 7000 is 7100 – 7000 = 100
Variety of contour lines is 4 between 7000 & 7100.
Add 1 to 4, 4 + 1 = 5
Now divide 100 by 5,
100/5 = 20 units
Uses of Contour Intervals in Surveying
- It is employed when an enormous space is to be mapped to a bijou piece of paper.
- A loftier contour interval is employed for an even colossal area & miniature contour intervals for a bijou area.
- In a much sizeable map, index contour lines are much less to keep up the map effortless to learn; during this case, to search out the loftiness of the intermediate point, the contour interval is employed.
- Earthquake approximation for bridge, dam or road will be found with the assistance of contour intervals within the map.
Reading Contour Lines
- The contour lines show a form of the world.
- One contour blotches an identical altitude line, which implies that if the isometric line measures an altitude of 1,000 feet above average water level, all points along that line are 1,000 feet above average water level.
- The contour lines never intersect, as one point on the map cannot have two distinct altitudes at an identical time.
- The remoter the contour lines pop up on the map, the polished the slant of the world is.
- The nearer the contour lines pop up, the further inclined the terrain are going to be.
Where the contour lines get very nearer & almost precipice occurs, the relief may be a perpendicular cliff, the contour lines almost move & may look as if they have coalesced.
- Pending cliffs can have one line crossing over another with one line appearing as dotted. There are 3 varieties of contour lines you’ll see on a map: intermediate, index, and supplementary.
- Index lines are the chunkiest contour lines & are generally blotted with numbers at one point along the line. This signifies the elevation above water level.
- Intermediate lines are the slender, more ordinary, lines between the index lines. They conventionally haven’t got a variety of labels. Generally 1 index line arises for each 5 intermediate lines.
- Supplementary lines pop up as dotted lines, designating leveled terrain.
What Is Importance of Topographic Maps?
Topographic maps are an immensely vital tool because they’ll represent the 3-dimensional landscape in 2 dimensions.
Anyone who can interpret a map from above can discover the position of peaks, valleys, mountain intervals, & saddles, among other land features.
Topographic maps may additionally express whether you’re traveling up or down a particular road or trail.
A topographic map series utilizes a conventional identification that features the range of cartographic symbols employed, in addition as a customary geodetic framework that defines the projection, organization, ellipsoid & geodetic datum.
Official topographic maps additionally embrace a national grid referencing system.
- Land Features: The structure of the contour lines can denote the form of the landforms in a specific region. For instance, concentric circles denote a zenith, with the tiniest circle blotting the summit.
- USGS Maps: Today, the USGS has generated quite 54,000 maps, which form the premise of most commercially attainable topographic maps today.
The maps also show power lines, rivers, glaciers, & mines.
- Orienting the Map: To combine a topographic map with the encompassing landscape, which can allow you to spot features like mountains and rivers, it’s vital to make sure that the map is aligned flawlessly.
What Is Contour Interval on this Map?
Contour lines are critical to realizing the elevation profile of your terrain or a specific land formation. This information is frequently obliging when selecting a hiking route… or lifesaving in an extraordinarily desperate survival condition.
Beyond backpacking & hiking, innumerable other livelihoods utilize them – land surveyors, foresters, engineers, miners, geologists, hunters, to call some.
Topography is that the study of geographical characteristic features on a landscape. A map with contour lines thereon is named a topographic map.
Topographic maps utilize a blend of tints, shading & contour lines to represent changes in elevation & terrain shape. Essentially, topographic maps represent the 3-dimensional panorama of Earth within the 2-dimensional gap of a map.
Understanding Line Formations
- Peak Ring: The innermost disc at the middle of diverse contour loops nearly always represents a loft.
- Depression Ring: Occasionally, however, an intramural ring denotes a depression (lowest elevation), in which the map will pop up with a sequence of bijou tick marks pointing towards the middle (called hachures).
- Cliff: If you see two or more lines coincide until they appear as one line, this represents a cliff. Beware, however – some cliffs might not pop up on the map.
- Valley: When contour lines intersect a valley or a stream, they generate a tapered V or U-shape. Rivers, of course, are denoted by blue lines which will run through the middle of the V-shape.
- Ridgeline: Consider a ridgeline like a lengthened loft, not coming to a fine point. Rather than a closed camp, a ridgeline can pop up as if a brobdingnagian ellipse.
- Saddle: A saddle may be a shallow area between two loftier points of elevation. They seem as hourglass shapes between 2 concentric circles.
- Ledge: Ledges or flat areas on the side of a mountain pop up as bulging U-shapes that time far from the loft.
What Is the Contour Interval on This Map?
- A 25 feet
- B 10 feet
- C 50 feet
- D 100 feet
Contour interval is that the vertical distance between the 2 contour lines which are next to every other.In the given figure contour interval is 50 feet.
It’s determined as follows:
- Let’s take an instance of 2 contour lines which are labeled.
- Point D is blotted at 10,000 lofts & additionally the next label is blotched as 10500 lofts.
- 10500-10000 = 500 feet
- Between these 2 contour lines, if we count, there are 10 counter lines.
- 500/10 = 50
- i.e. each counter line has 50 feet distinction.
- We can cross-examine it as follows.
50 x 10 ( as there are 10 contour lines between 10.500 labelled & 10000 labelled points ) = 500 feet.