2/14/2024 0 Comments Contour definition in inspectionThe final step is the quotient of the difference between 2 index lines (step 2) and the number of lines in between two index lines plus 1 (step 5). The number of lines obtained in the above step is taken and added with 1.įor Ex: If the number of lines between 2 index lines are 5. Now count the number of non-index lines contour lines between the 2 index contour lines selected for the contour interval calculating in the 1 st step. To take the difference, subtract the higher elevated line with the lower elevated line reading. Now calculate the difference between the two-selected index contour line selected from a map. The calculation of the contour intervals is as below:įirstly locate 2 index contour lines that are labeled with a specific elevation. In the above figure, the dark lines with reading are index contour lines. These marked or labeled lines are known or termed as Index Contour Lines. To keep the contour map simple and easy to read, not every contour line is marked with its elevation reading. How to Calculate Contour Interval from Maps?Ī contour map consists of contour lines of a given geographical region. If the ground has large variation in levels, for instance, hills and ponds If a detailed map is to be prepared for execution work Select Low CI like 0.5m, 0.25m, 0.1m or lessįor small scale maps covering a wide area of varying terrainįor rough topographical map meant for initial assessment only The selection of the contour interval is decided by the survey leader before the start of the mapping process depending upon the ground factors. The commonly used contour interval is 20 feet for a 1:24,000 map scale.įactors Affecting the Selection of Contour Interval When the contour interval is not specified in the map, it can be calculated as explained in the following sections. In every map, on the right-hand bottom side, the contour interval is specified. Considering the size of the area to be mapped, contour intervals are assumed. Usually there are different contour intervals for the different maps. □ Reading time: 1 minute What is Contour Interval?Ī contour interval in surveying is the vertical distance or the difference in the elevation between the two contour lines in a topographical map.
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