What Is an Interval on a Contour Map?


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What Is an Interval on a Contour Map?

A contour interval in surveying is the vertical distance or the distinction in the elevation between the two contour traces in a topographical map. Usually there are special contour intervals for the distinct maps. Considering the measurement of the place to be mapped, contour intervals are assumed. In each map, on the right-hand backside side, the contour interval is specified. When the contour interval is no longer distinctive in the map, it can be calculated as defined in the following sections. The normally used contour interval is 20 ft for a 1:24,000 map scale.

Calculation Of Contour Interval

These index traces will be mentioned with their elevation. Discover the elevations of two adjoining index lines. The largest quantity shows the uphill rise. Locate the distinction between the two elevations.

A contour map incorporates contour traces of a given geographical region. To hold the contour map convenient and comprehensible to read, no longer each contour line is marked with its elevation reading.

These marked or tagged strains are remembered or termed index contour Lines. In the above picture, the darkish traces with studying are index contour lines.

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Characteristics of Contour in Surveying

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

  1. The horizontal distance between any two contour traces suggests the quantity of slope and varies inversely on the quantity of slope.
  2. Two contours of exceptional elevations by no means move every different barring in the case of an overhanging cliff.Contours of various elevations by no means unite to
  3. structure a single contour without in the case of a vertical cliff.
  4. Contours that are shut to every different depict a steep slope whereas the contours drawn aside depict a mild slope.
  5. The equally spaced contours depict a uniform slope. When the contours are drawn parallel, equidistant, and straight, such contours point out inclined aircraft surfaces.
  6. A contour line need to shut itself however may also no longer always be inside the limits of the map itself.
  7. Contour at any factor is perpendicular to the line of the steepest slope at that point.
  8. Irregular contours point out uneven surfaces.
  9. The equal contours should show up on each the aspects of a ridge or a valley.

Uses of Contour Intervals in Surveying

  • When a massive location is to be mapped in small piece of paper contour intervals are used. A greater contour interval is used for a giant region and small contour interval for small area.
  • In a giant map, index contour strains are much less to preserve it easy to examine the map easily. In this case, to discover out the intermediate factors elevation, contour intervals are used.
  • Earthwork estimations for any kind of shape like bridges, dams or roads can be discovered out with the assist of contour intervals in a map.
  • As contour intervals are for the calculation of vertical elevation of an area, identical way to calculate the horizontal distance it is termed as Horizontal Equivalent. The horizontal distance between two factors on two consecutive contour strains for a given slope is recognised as horizontal equivalent. The distinction between Contour intervals and

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Advantages of Contour Interval

  • It indicates the slope and dimension of extraordinary landforms on the map.
  • By searching at the contour intervals it is convenient to calculate the quite a number elevations of the landscape.
  • It can be utilized in drawing cross-sections of the particular facets on the mapped area.

Disadvantages of Contour Interval

  • Contour fail to symbolize a few of the heights due to the problem of the vertical interval.
  • Some of the landforms can't be represented by using making use of contours. For instance coral reef, outcrop rock, and craters.
  • The contour approach is now not utilized to signify remedy on a small-scale map as it may also doubtful a few details.

Contour Lines in Detail

Contour traces have a variety of points in frequent regardless of the land proven on a given map. Some of these are evident at a glance, however you can also now not admire them or their importance besides a formal explanation.

Contour traces have the following prevalent characteristics:

  • They by no means pass every other, divide or split.
  • Closely spaced contour traces symbolize steeper slopes, whilst traces that are spaced some distance aside depict gentler inclines and declines.
  • They create upward traits on the facets of valleys and shape a V- or a U-shape at circulation crossings.

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How to Find Contour Interval?

The calculation of the contour interval,

  • Considering the above map for the calculation of intervals, the steps worried in contour interval computation.
  • Let’s expect two index contour lines, 7000 and 7100, and compute the interval between them.
  • The distinction between the two chosen index contour strains 7100 and 7000 is 7100 – 7000 = 100
  • Now depend the quantity of non-index traces contour traces between 7000 and 7100 as 4.
  • The wide variety of strains received in the above step is four and introduced with 1.
  • Adding, four + 1 = 5
  • Now divide a hundred with the aid of 5, 100/5 = 20 gadgets
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