Quick Answer: What Is A Index Line?

What 2 types of lines show elevation differences?

Contour lines are used to show elevation on a topographic map.

Lines or isolines on a map that connect points with the same elevation.

What does each contour line on a map show.

Each contour line shows a different elevation..

What is the distance between two contour lines called?

contour intervalThe elevation difference between two adjacent contour lines is called the contour interval (CI). Usually the contour interval is noted on the map legend. In most topographic maps every 5th contour line is drawn in bold print or wider than other contours. Such lines are called index contour lines.

How many types of contour lines are there?

3 kindsThere are 3 kinds of contour lines you’ll see on a map: intermediate, index, and supplementary. 1. Index lines are the thickest contour lines and are usually labeled with a number at one point along the line. This tells you the elevation above sea level.

What information does the slope tell you?

The slope of a line is the change in y, y (read “delta y”), divided by the change in x, x (read “delta x”). That is, slope is , which is a rate of change. Stating the units for y and x will help clarify what the slope tells you about how the y-value changes from one x-value to the next.

How do you read contour lines on a site plan?

Closely spaced contour lines indicate steep slope. Widely spaced contour lines indicate gentle slope. Equally spaced contour lines indicate uniform slope. Closed contour lines with higher elevation towards the centre indicate hills.

How do you find the slope of a contour line?

Measuring slopes on a contour map: – Slope = “rise over run”, or vertical height increase over horizontal distance. – Example: if two contour lines are 300 m apart (use map scale to find the distance between them!) and they represent elevations 50 m apart, then rise = 50 m, run = 300 m. Slope = 50/300.

What is the index contour line?

Index contours are bold or thicker lines that appear at every fifth contour line. If the numbers associated with specific contour lines are increasing, the elevation of the terrain is also increasing. If the numbers associated with the contour lines are decreasing, there is a decrease in elevation.

What are the 5 Rules of contour lines?

Rule 1 – every point of a contour line has the same elevation. Rule 2 – contour lines separate uphill from downhill. Rule 3 – contour lines do not touch or cross each other except at a cliff. Rule 4 – every 5th contour line is darker in color.

How do you read a lot plan?

Tips on How to Read a Site PlanFind The Title Block. In the bottom right corner of most plans, you’ll find what’s called a title block. … Learn the Plan’s Scale. … Determine the Orientation of the Plan. … Know the Datum Point. … Note the Site’s Contours. … Locate Existing Structures.

Why can’t contour lines cross?

Contour lines can never cross one another. Each line represents a separate elevation, and you can’t have two different elevations at the same point. … Moving from one contour line to another always indicates a change in elevation.

How do contour lines work?

Contour lines are lines drawn on a map connecting points of equal elevation, meaning if you physically followed a contour line, elevation would remain constant. Contour lines show elevation and the shape of the terrain. … In order to keep things simple, topographic maps show lines for certain elevations only.

How do you find the index contour?

To make topographic maps easier to read, every fifth contour line is an index contour. Because it’s impractical to mark the elevation of every contour line on the map, the index contour lines are the only ones labeled. The index contours are a darker or wider brown line in comparison to the regular contour lines.

What do contour lines mean?

Contour line, a line on a map representing an imaginary line on the land surface, all points of which are at the same elevation above a datum plane, usually mean sea level. map: contour lines. The diagram illustrates how contour lines show relief by joining points of equal elevation.

How do you contour a survey?

In this method, the contours to be located are directly traced out in the ground by locating and making a number of points on each contour. These points are then surveyed and plotted on plan and the contours drawn through them.