 In maps and relief the representation of the feature are very important. Now these features are actually related with the nature phenomena as well as human phenomena. So both phenomena are actually over the surface of the earth and we call them the nature environment and human environment. So before going to discuss the techniques of representation of the relief features we must know what is elevation. So the term elevation means the height of the land surface above a fixed plane. So this fixed plane may be the sea level. The height is measured in feet or any other unit. Then the term relief is very important. So before going to discuss the representation of relief features we must know what is relief. The term relief is used in a systematic sense. It indicates the variation in the nature of the land surface. It shows the heights of the highlands and as well as the lowland like the mountains of Pakistan are to the north of the country. So most of the north of the country is covered with highlands. It may be from 20,000 to 25,000 feet above sea level but the lower city is at 700 feet above sea level. So gradually the heights are decreases when you are moving from north to the south of the country. Now this slide shows not only the lowland areas of the region which is closer to the sea level but it also shows the highlands of the area. So all the heights are from sea level. So this is actually the area which is called the sea level. Every country has its own sea level is called the datum of the country. Now this map is actually the relief map of the world. It covers not only the places of the highlands of the earth but also the lowlands. It also shows the shallow area of the water which is closer to the continent and the deep land of the oceans which is to the center of the ocean. Now the countries which are actually under the highland areas are in brown color. So like this is actually the south of the China and north of the India, north of Pakistan is covered with highland. But the green color shows the most of the land which is under lowland areas. So all the heights are actually in different colors but the darker shade show when you are dealing with the water it shows the deep water. The light shade of the water shows the shallow water. But in land the darker color shows the highlands and the green color shows the lowland areas. Now when we are representing the relief feature over the map there are two methods. The first method is called the mathematical method and the second method is called the pictorial method. Then it is actually we are giving the more or less true visual picture of the elevation and relief we are using these two methods. In mathematical method the contours are very important. Contouring is the standard method of representing relief or actually the imaginary lines of the ground joining places of same height above sea level. These lines are fixed by accurate surveys. Now all the lines which are actually in circle are called the contours. These are in circle and joining places of same height but it start every contours start from mean sea level. The second circle is higher than the previous one is it has a height of 10 feet then 20 feet above sea level 30 feet above sea level 40 50 and 58 is the highest point of the area. So you can see the true representation of the contours which are actually depicting the mod of a place. Every contour has a surveyed point so that is why is true representation of the relief feature. The contour interval of a contour map is the difference in elevation between successive contour lines between two contour line is actually called the contour interval. So if we have a difference of 10 feet above sea level so the contour interval is 10 feet. If it has 100 feet so contour interval is 100. Now this is the slide of a given place where we have two places regarding the contour interval. This area has the steep slope it means the contour interval or the distance between two contour is low but this shows the gradual slope it means the contour interval between the two contour line is high so it means the space between the two contour is actually dealing with the slope of the area. The next method of representation of the relief feature is the spot height it gives the actual height of the place above sea level fixed by a surveys they show a height values. So as shown here the contour lines have more space and less space but the important spots whose height can be like city or a peak or a mountain top or a place which has an administrative point of view is very important so its height when we write it that is called the spot height of the area but all are controlled by the contouring so those are actually the true heights of the area which are surveyed by certain techniques. The central part of this area is under gradual slope so it may be covered with agriculture land but sides are actually under high steep slopes or which are under drainage system so the valleys are there or streams are going towards the from top to the bottom of the area. So we can write all these heights in words so in this slide we can see a spot or a place where the building is located and its height is mentioned there.