#CONTOUR MEANING IN SURVEYING HOW TO#
#CONTOUR MEANING IN SURVEYING PLUS#

A higher contour interval is used for a bigger area and shorter contour intervals for a smaller area.Contour interval is used when a big space is to be mapped to a small piece of paper.The horizontal level varies with the slope, nearer distances indicate a steep slope and a wider distance signifies a mild slope. The contour interval in a given map is constant. The distance needs to be measured on the map and multiplied with the dimensions of the map to be transformed to actual distance. Measurement or scaling is not required because contour levels are indicated on contour lines. The horizontal distance between two factors on two contour lines for a given slope is known as the horizontal equivalent. Difference between Contour interval & Horizontal equivalent: Contour interval Horizontal equivalent The contour interval is used to calculate the vertical elevation of a location. The contour interval of the above map gave us 20 units. The variety of contour lines is 4 between 70. Now the difference between 71 is 7100 – 7000 = 100. Let’s say, 70 and calculate the interval between them. Example contour interval calculation:Ĭonsidering the map, the following steps are used to calculate the contour intervals calculation as follows: The final answer is obtained by dividing the contour intervals of the particular topographic map.

#CONTOUR MEANING IN SURVEYING PLUS#

The ultimate step is the quotient of the difference between the index lines (step 2) and the variety of lines between the 2 index lines plus 1 (step 5). The variety of lines obtained within the above step is taken and added with 1.įor example: if the variety of rows between 2 index lines is 5, then add 1 to 5 which turns into 6. Now calculate the number of non-index lines contour lines between the two indexed contour lines chosen for the contour interval calculated in the 1st step. To take the difference, subtract the upper elevation line with lower elevation line. The calculation of the contour intervals is as follows:įirst, find the two index contour lines which can be labelled with a particular height.Ĭalculate the difference between the 2 selected index contour lines from a map. To maintain the contour map easy and simple to learn, every contour line is not marked by its elevation studying, these marked or labelled lines are identified or known as index contour lines.

#CONTOUR MEANING IN SURVEYING HOW TO#

How to Calculate Contour Interval from Maps?Ī contour map consists of contour lines of a given geographic area. Time and resources available: If much less time and resources can be found. Nature of ground: If there’s a massive change in ground levels, for example, hills and ponds. If a detailed map is to be prepared for the execution work. Extent of the survey: For rough topographic map means for preliminary assessment only. For large maps showing details of a small area. Scale of the map: For small scale maps covering a large area of different areas. Select Low CI like 0.5m, 0.25m, 0.1m or less. Factors: Select High CI like 1m, 2m, 5m or more. The choice of the contour interval is determined by the survey leader before the beginning of the mapping process based on ground factors as follows. Factors Affecting the Selection of Contour Interval: When the contour interval is not specified within the map, it may be calculated within the following sections, the generally used contour interval is 20 feet for a 1: 24,000 map scale. Discuss the Various Height Concepts Found In Surveyingįor the plotting of region, the contour intervals are assumed, the contour intervals is specified on the right-hand side.

Contour meaning in surveying