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In today’s class, we will be talking about the representation of relief landforms. Enjoy the class!
Representation of Relief Landforms
Conventional signs are symbols used to represent both natural and human features found in an area that is represented on a map. The conventional signs represent the language of the map. The map reader cannot read any map without the use of the signs. They are usually shown at the bottom of all topographical maps where the symbols are found. From these signs, information on the map can easily be interpreted e.g
+ This sign represents hospital or dispensary.
+++++++++ This represents a railway line.
========== This sign represents a main road.
METHODS OF REPRESENTING RELIEF
The relief of an area refers to the position and character of the highlands and lowlands in that area.
METHODS OF SHOWING RELIEF ON MAPS
- Spot Height: These are spot or points on the maps whose height above the sea level has been accurately measured.
- Hill Shading: In this method, only one colour is used but the intensity or thickness of the colour depends on the steepness of the hill. The higher the hill, the deeper the shade representing it.
- Trigonometrical Stations: These are simple points on the ground marking the angle of triangulation when mapping an area. They are usually represented by a triangle and a dot in the middle, with the height written by the side.
- Form Lines: These are lines drawn on a map like contours but are based on estimations. They are not as accurate as contours and they are represented by broken lines.
- Contours: These are lines drawn to join places of equal height level or altitude. The sea level is taken as the starting point in all measurements in metres or feet. The height of a particular point is written on the line.
- Hatchures: These are short lines drawn down the slope in the direction of the steepest gradient. The steeper the slope the heavier the lines which are used.
- Contour Layering: As an aid to visual impression, the space between contours are often coloured or tinted. Different shades of colours are used to denote differences in height e.g green represents a low land, yellow and brown represent highlands and white represents snow-capped peaks. Blue represents water bodies and the darker the blue, the deeper the sea.
- Benchmark: This is a permanent mark made on objects like walls, building and bridges. It indicates the actual height which is usually written on the object. In most cases, it is written along the road.
DRAWING OF RELIEF PROFILE AND DETERMINING INTERVISIBILITY
Relief profile or cross-section is the practice whereby relief shown by contour on the map is drawn to bring out the real appearance of such relief as it is on the ground. It shows the nature of the relief that is represented by contour lines on a map.
STEPS/PROCEDURE FOR CROSS-SECTION DRAWING
- Draw a straight line to join the two points to be drawn.
- Place a strip of paper on the section line and mark all the points at which contours cross the line. Number the marked contours down vertically. The rise and fall in the lines should be indicated respectively.
- Transfer the strip of paper to the point of the scale of height and at each point draw a vertical line to the corresponding height on the scale.
- A smooth line should be drawn to join up the points.
Intervisibility is defined as a way of knowing whether one point or place on the map can be seen from another point or place on the same map.
- A point at the peak of a conical hill is visible to another point at the base of the hill.
- A concave slope gives room for intervisibility between two points while a convex slope does not.
- Two points on the same contour lines are intervisible when all the contour lines between them are at the same point or lower than the two points.
INTERPRETATION OF TOPOGRAPHICAL MAPS
Topographical maps are maps that show the relief and important features of a place. Geography students need to be able to interpret topographical maps either with or without the use of conventional signs. Important features that need interpretation are relief, drainage, settlement communication and land use.
Interpretation of relief
- Use contour lines, spot height, trigonometrical station to note the highest point and the lowest point on the land. The highest point is found on the highest contour lines.
- Note the proportion of the land occupied by highlands and lowland.
- Note the specific landform or relief whether a ridge, hill, knoll or plateau.
- Note the location or direction of the relief features on the map.
- Note the height of the lowlands above the sea level and whether they are flat plains or undulating.
- Note if the hills and plateau are dissected or not.
Interpretation of drainage
- Find out the important rivers on the map.
- Note the direction of flow of the rivers.
- Find out the pattern of drainage on the map whether radial, trellis or dendritic.
- Look out for watersheds which separate drainage system.
- Note if there are marshy areas which are usually poorly drained and are liable to flooding.
- Note if there are water bodies like river, sea, ocean or ake. Identify their location on the map.
- Determine whether the river has a delta or an estuarine.
Interpretation of settlement
- Find out the type of settlement, either rural or urban.
- Note the pattern of settlement whether linear, nucleated or disperse.
- Relate the settlement to relief i.e. is the settlements located on highlands, plateaux, ridges or lowland?
- Relate settlement to drainage i.e. are settlements along the river course, far from rivers, near a lake, ocean or far from marshy areas? And give reasons for such settlement.
- Relate settlement to communication i.e. is the settlement linear i.e. along the road, railway, far from the airport, or along a navigable river or lake?
- Describe also areas which are not settled and give reasons why they are uninhabited.
Procedures for interpreting communication
- Find out the means of communication i.e by road, railway, footpath, air (if there are airports) and rivers (if there are navigable rivers).
- Note from conventional signs: If the roads are primary, secondary or minor.
- Relate communication to relief: Do the roads, railways or footpath avoid steep slopes, passes through highlands, ridges or are they located on the lowlands? Are there passes? Etc.
- Relate communication with the settlement: the presence of major roads is an indication of commercial or industrial towns while minor roads and footpath are common features of rural settlement.
- Note important natural and man-made features like mountains, boreholes, ridges which one may come across when travelling from one area to another.
Land use refers to the various ways in which man uses the land i.e. the use of land by man is a reflection of the function of that settlement. The use of land or the function of a particular settlement can best be determined from the conventional symbols usually found below all topographical maps.
FEATURES FROM CONVENTIONAL USES OF LANDS OR FUNCTIONS
SIGNS ON A MAP OF A SETTLEMENT
|1. Presence of banks & markets||Commercial|
|2. Presence of mineral resources||Mining|
|3. Presence of rivers||Fishing and canoe building|
|4. Presence of hotels and stadium||Social function|
|5. Presence of schools||Educational function|
|6. Presence of marshy area||Swamp rice cultivation|
|7. Presence of industries||Industrial functions|
|8. Presence of forest||Farming and lumbering|
|9. Presence of grasses||Livestock|
|10. presence of prison, court, police station.||Administration|
|11. Presence of buildings||Residential|
|12. Presence of hospital, dispensary||Health function|
- State three procedures in interpreting communication on topographical maps.
- What do you understand by “land use”?
- Explain map reduction.
In our next class, we will be talking about World Population. We hope you enjoyed the class.
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