How to Determine Contour Interval?

Before getting ready a contour map, the required contour interval is decided. Taking into account the following elements on which the contour interval depends

Surface: The Nature Of The Floor Surface
Map Scale
Purpose And Extent Of The Survey
Time And Expense Are Required

What is Contour Interval?

A contour interval in surveying is the vertical distance or the distinction in the elevation between the two contour strains in a topographical map. Usually there are exceptional contour intervals for the distinctive maps. Considering the dimension of the vicinity to be mapped, contour intervals are assumed. In each and every map, on the right-hand backside side, the contour interval is specified. When the contour interval is now not distinctive in the map, it can be calculated as defined in the following sections. The often used contour interval is 20 ft for a 1:24,000 map scale.

Steps of Calculating Contour Intervals

Step 1:

At first, we want to detect two index contour traces that are given with a particular elevation.

Step 2:

Now locate the distinction between the two chosen index contour traces from a map. To observe the difference, now minus the greater expanded line with the decrease extended line reading.

Step 3:

We want to calculate the variety of non-index strains contour strains between the two index contour strains chosen for the contour interval calculated in step 1.

Step 4:

The range of traces calculated in the above step is cited and delivered with 1. Let take a easy example: If the variety of traces between two index traces is 5. Then add 1 to 5 that will be 6.

Step 5:

The closing and last step is the quotient of the distinction between two index traces (step 2) and the range of strains in between two index strains provides 1 (step 5).

Step 6:

The end result we calculate after dividing is the contour interval of the given topographical map.

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Characteristics of Contour in Surveying

The most important attribute of the contour can be listed as follows:

The horizontal distance between any two contour strains shows the quantity of slope and varies inversely on the quantity of slope.
Two contours of one of a kind elevations in no way pass every different without in the case of an overhanging cliff.
Contours of various elevations in no way unite to structure a single contour barring in the case of a vertical cliff.
Contours that are shut to every different depict a steep slope whereas the contours drawn aside depict a mild slope.
The equally spaced contours depict a uniform slope. When the contours are drawn parallel, equidistant, and straight, such contours point out inclined aircraft surfaces.
A contour line ought to shut itself however may additionally no longer always be inside the limits of the map itself.

Rules of Contour Lines

Every factor on a contour line is of the specific identical elevation. In different words, contour strains join factors of equal elevation.
By definition, contour traces separate factors of greater elevation from factors of decrease elevation. This capacity it is usually feasible to outline an “uphill” path on one facet of a contour and a “downhill” path on the different side.
Contour traces in no way cross. They may additionally come very close to every different (e.g. alongside a cliff), however by way of definition they can also in no way go every other.* This is because one vicinity on the floor of Earth can't be at two distinct elevations!
Contour traces in no way split. Instead, contours shape closed loops. These loops observe the form of the land, and may additionally lengthen previous the side of the map.
Closely spaced contours point out a steep slope, whereas contours that are spaced a long way aside point out a gentle slope or nearly flat surface.

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Advantages of Contour Interval

It suggests the slope and dimension of exclusive landforms on the map.
By searching at the contour intervals it is handy to calculate the a number elevations of the landscape.
It can be utilized in drawing cross-sections of the particular points on the mapped area.

Disadvantages of Contour Interval

Contour fail to symbolize a few of the heights due to the trouble of the vertical interval.
Some of the landforms can't be represented by using utilising contours. For instance coral reef, outcrop rock, and craters.
The contour technique is no longer utilized to characterize comfort on a small-scale map as it may also uncertain a few details.