Contour lines are the biggest distinguishing function of a topographic map. Contour traces are traces drawn on a map connecting factors of equal elevation, that means if you bodily accompanied a contour line, elevation would continue to be constant. Contour strains exhibit elevation and the structure of the terrain. They’re beneficial due to the fact they illustrate the form of the land floor — its topography — on the map. Here’s a cool way to recognize how to interpret contour lines: Take an object like a ball or a pile of laundry, and shine a pink laser pointer alongside the object’s side. The line you see will appear like a contour line on a topographic map.
In order to hold matters simple, topographic maps exhibit traces for positive elevations only. These strains are evenly spaced apart. We name this spacing the contour interval. For example, if your map makes use of a 10-foot contour interval, you will see contour traces for each 10 toes (3 meters) of elevation — strains at 0, 10, 20, 30, forty and so on. Different maps use specific intervals, relying on the topography. If, for example, the ordinary terrain is pretty elevated, the map may run at 80- to even 100-foot (24- to 30-meter) intervals. This makes it less difficult to examine the map — too many contour traces would be challenging to work with. Look in the margin of your map to discover out its contour interval.
Example Calculation of Contour Intervals
Taking the given maps, the steps wanted in contour interval calculation are,
Let us take, 7100 and 7200 and locate the interval between them. Now the difference between 7200 and 7100 is 7200 – 7100 = a hundred The variety of contour strains in-between 7200 and 7100 is four Adding 1 we get, four + 1 = 5. Now we want to divide a hundred by way of 5, 100/5 = 20 units.
The Contour Interval of the given map is 20 Units.
Also Read: What Is Dry Pack Mortar
What Is a Contour Interval?
The first-class way to familiarize your self with the thinking of contour strains and contour intervals is to learn about the legend of the map, which tells you how some distance aside in vertical toes or meters adjoining contour strains are. This would possibly be a wide variety handy to each math (such as 10 meters, or 20 or forty feet) and the truth of the neighborhood terrain.
How to Calculate Contour Interval from Maps?
A contour map consists of contour traces of a given geographical region. To maintain the contour map easy and convenient to read, no longer each and every contour line is marked with its elevation reading. These marked or labeled strains are acknowledged or termed as Index Contour Lines.
Firstly discover two index contour strains that are labeled with a unique elevation.
Now calculate the distinction between the two-selected index contour line chosen from a map. To take the difference, subtract the greater multiplied line with the decrease increased line reading.
Now depend the wide variety of non-index strains contour strains between the two index contour strains chosen for the contour interval calculating in the 1st step.
The wide variety of strains acquired in the above step is taken and delivered with 1. For Ex: If the quantity of traces between two index traces are 5. Then add 1 to 5 that turns into 6.
the ultimate step is the quotient of the distinction between two index strains (step 2) and the wide variety of strains in between two index strains plus 1.
Also Read: Traffic Rotary
Types of Contour Lines
There are three kinds of contour strains detected on a map,
- Index Contour Line
- Intermediate Contour Line
- Supplementary Contour Line
Uses Of Contour Interval In Surveying
The makes use of of contour interval in surveying are as follows,
- Interval is utilized when a giant area is to be mapped to a small piece of paper.
- A greater interval is utilized for a large vicinity and smaller intervals for a smaller area.
- In a large map, index contour strains are lots much less to keep the map and are easy to learn.
- To locate the top of the intermediate point, the interval is utilized.
- Earthquake estimation for the dam, bridge, or street can be observed with the assist of contour intervals inside the map.
- As intervals are for the computation of the vertical elevation of an area, a similar way to compute the horizontal distance is termed Horizontal Equivalent.
- The horizontal distance between two factors on two consecutive contour strains for a supplied slope is recognized as the horizontal equivalent.
Also Read: Types of Formwork