How to Find the Contour Interval of a Map?

To discover contour interval divide the distinction in elevation between the index strains via the range of contour traces from one index line to the next.

For example, if the distance 200 is divided by means of the quantity of lines, the place the range of strains is 5. The contour interval is equal to 200 / 5 = 40, or 40-unit contour intervals.

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 distinct contour intervals for the distinct maps. Considering the measurement 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 no longer designated in the map, it can be calculated as defined in the following sections. The oftentimes used contour interval is 20 ft for a 1:24,000 map scale.

Computation Of Intervals

The computation of the contour intervals is as below,

• Step 1:-First of all, discover two index contour strains that are named with a unique elevation.
• Step 2:-Now compute the distinction between the two chosen index contour strains hooked up from a map. To achieve the difference, subtract the greater increased line from the decrease accelerated line reading.
• Step 3:-Directly matter the variety of non-index line contour strains between the two index contour strains targeted for the contour interval computing in the 1st step.
• Step 4:-The variety of traces obtained in the above step is acquired and delivered with 1. For Example: If the range of strains between two index strains is 5. Then add 1 to 5 which will become 6.
• Step 5:-The closing step is the quotient of the distinction between two index traces (step 2) and the wide variety of traces between two index traces plus 1 (step 5).
• Step 6:-The closing reply we get after dividing is the contour interval of the precise topographical map.

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Uses Of Contour Maps

• You can select a appropriate web site for your building activity.
• You can decide the reservoir capacity.
• Alignment of roads, canals and transmission strains is carried out correctly thru contour lines.
• The traits of the floor can be determined.
• Earthwork quantity estimation.
• Ground traits (e.g. flatness, uniformity, sloping, undulations or hills, etc.)
• Using the contour map, you can pick out the most suitable and cost-efficient web page for your work, such as roads, railroads, canals, pipelines, dams, and reservoirs.
• The quantity of reservoir storage water, cuts and embankments can be estimated the usage of contour lines.
• You can use contour traces to sketch navy operations.
• They are used to reap statistics used in the sketch and development of irrigation constructions such as dams.

Purpose of Contour Maps of Existing Ground

• In order to sketch a new bodily infrastructure, it is very necessary to be aware of the place are the low factors or excessive factors throughout the undertaking area. This will assist designers to graph the tiers of the proposed street or railway traces in a comparable manner to minimise large cuttings or embankments.
• In an city or rural setting, low-lying areas are many times used for drainage outfalls and join to current rivers or ponds or canals. So producing a contour map of current floor helps designers to graph the proposed drainage community accordingly.
• Low-lying areas (close to rivers or canals) are susceptible to flooding. Meteorological Departments use Contour Maps to inform the public about flood-prone locations. Design organizations use this information’s graph new infrastructure initiatives in such a way that similarly harm or in addition flooding can be avoided.

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How to Read Contour Lines and Calculate Contour Interval?

Contour traces very shut to every different signify steep slopes, whereas contour traces with comparatively large distances signify mild slopes. If there is a big area between two contour lines, then it represents a flat spot location.

Increasing order of contour interval represents a hilly terrain floor and reducing order of contour interval represents a valley or ridge kind surface.

Contour strains by no means move every other. If you locate a place the place a contour line crosses any other contour line, it capacity there is an error whilst producing the contour map. However, contour strains can merge to one point. For example, if there is a vertical cliff at one point, the contour strains will be proven as merging at one point.

Concentric circles form of contour line with growing order of contour interval represents a cone-shaped hilly terrain.

Concentric circles form of contour line with lowering order of contour interval represents a cone-shaped deep valley.

Equally spaced contour represents a uniform slope and these kinds of contour maps are typically considered in a criticism avenue diagram proposal. Irregular contour traces signify an uneven floor floor and are in many instances viewed when maps are created from a topographic survey of greenfield land.

What are the elements that have an effect on the choice of contour intervals?

The contour interval relies upon upon the following factors.

1. Nature of floor surface:

Plain ground: The contour intervals are normally small & are parallel.

Steep slope: The contour intervals are normally huge & are unequal

2. Scale of the map:

The contour spacing will be massive for a map having a small scale. For the large scale map, the contour intervals are made of much less spacing.

3. Purpose:

For the unique & unique survey work, the contour interval ought to be smaller. For the difficult survey work such as vicinity survey, discovering catchment area, discovering the ability of water bodies, etc. we want large contour intervals.

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