Usefulness and setback of using maps
Map is scaled representation of part or whole of the earth's surface on two dimension surface such as paper wood or wall.
- Maps are used for recreational purpose such as traveling, hiking and orienteering
- Maps are used by government and industry to assist with urban planning, mining, emergence management and establishment of legal boundaries and land ownership
- Maps are very important in field studies
- Maps are used as storage of geographical facts of represented.this makes map capable of giving insight to the previous appearance of the area
- Map are used in conducting wide range of of project like; building design, construction of roads and others of the same reflection
- Maps can be used to show relationship of various geographic phenomena like relationship between population and landscape.
- Maps uses symbols and signs to represent various features on the earth's surface
- Maps are selective since they show only selected information to appear on the maps
- Maps are more expensive to make compared to other geographic tools like photograph
- Maps takes long time to make to compared to other geographic tool like photograph
- The reading and interpretation of map need high skills
- Map are not capable of recording and keeping instant data
Maps come in an infinite variety of sizes and styles and serve a limitless diversity of purposes. Regardless of type, however, every map should contain a few basic components to facilitate its use Omission of any of these essential components decreases the clarity of the map and may make it more difficult to interpret.
Title: This should be a brief summary of the map’s content or purpose. It should identify the area covered and provide some indication of content, such as “Road Map of Kenya,” or “River Discharge in Northern Europe.”
Date: This should indicate the time span over which the information was collected. In addition, some maps also give the date of publication of the map. Most maps depict conditions or patterns that are temporary or even momentary. For a map to be meaningful, therefore, the reader must be informed when the data were gathered, as this information indicates how timely or out of date the map is.
Location: Although the grid system of latitude and longitude is the most common system of location seen on maps, other types of reference grids may also be used on maps. For example, some large-scale maps (such as road maps) use a simple x- and y-coordinate grid to locating features (similar to that shown in Figure 1-11), and some maps display more than one coordinate system.
Legend: Most maps use symbols, colors, shadings, or other devices to represent features or the amount, degree, or proportion of some quantity. Some symbols are self-explanatory, but it is usually necessary to include a legend box in a corner of the map to explain the symbolization.
Scale: Any map that serves as more than a pictogram must be drawn to scale, at least approximately. A graphic, verbal, or fractional scale is, therefore, necessary.
ORIENTATION:a map should indicate which way is north (and/or south, east and west). Commonly this is done by a north arrow or compass rose. Orientation may also be shown by graticule or grid marks (e.g. lines of latitude and longitude). By convention north is towards the top of the page (thus some maps do not have north arrows), but the orientation must still be given for a 'proper' map. North does not have to be at the top of the page and a north arrow is essential in maps where it is not.
Data Source: For most thematic maps, it is useful to indicate the source of the data.
Projection Type: On many maps, particularly small-scale ones, the type of map projection is indicated to help the user assess the kinds of distortions on the map.
BORDER(s): a border identifies exactly where the mapped area stops. The border is often the thickest line on the map and should be close to the edges of the mapped area. The distance between the map and the border should be the same on all sides (balanced).
There can also be a border around the entire map layout (enclosing and grouping the title, legend, text boxes, etc.). Both of these borders are sometimes referred to as a 'neatline.' In addition, there is sometimes a thin additional line just outside of a border (accentuating it and ideally making it more visually appealing) that may also be referred to as a neatline.
PURPOSE: All maps have a purpose which should influence every element of the map and the map layout. A cartographer should be able to clearly articulate the purpose of their map and should keep the audience and the client in mind.
Climate is the average weather condition of a given area recorded over a very long period of time.
The topographic maps show little direct evidence of the climatic conditions. yet by looking at certain evidence one is able to describe the climate of the given mapped area.
The description of climate in the topographic map is based on two-element of climate namely temperature and rainfall since their variation can easily be explained by various evidence from the map.
Some hints in interpreting climate from topographic map:
Latitude of the area
latitude is the angular distance of a place north or south of the earth's equator, or of a celestial object north or south of the celestial equator, usually expressed in degrees and minutes.
Through studying latitude one is able to deduce the climatic condition of a given mapped area.
For example, in the area with a latitude 5 degrees north or south of the equator the area is considered to be in equatorial climatic condition while the area between 5 to 15 degrees north or south of the equator is in tropical climatic condition.
Presence of water bodies and drainage pattern
A general high density of streams indicates that the area receives high rainfall. in another case the presence of low density, intermittent or seasonal streams, salt lakes, and boreholes indicate aridity.
Vegetation
The presence of forest in the map indicates heavy rainfall while woodland vegetation indicates moderate rainfall. shrubs, thickets, and grassland indicate a dry condition or light rainfall
Crops
crops grow in those areas where water and temperature conditions are favorable for their growth.
For example, area with tea, coffee, and sugar cane indicate that area receives heavy rainfall. Crops such as cotton, sisal, and sorghum indicate medium rainfall
Relief/altitude
the altitude of features such as high mountain or mountain ranges and plateaus tend to have orographic rainfall and forest making them make their own mountainous climate.
Mountains do also create their own climate due to the effect of aspect which creates a rain shadow
HOW TO DESCRIBE DRAINAGE IN TOPOGRAPHICAL MAP
what is drainage
Drainage is the outflow of water through the system of natural rivers
what is drainage pattern?
A drainage pattern is a layout that a river and its tributaries, or set of rivers, make on the earth's surface. Some of the common river drainage patterns include dendritic river pattern, trellised river pattern, radial river pattern and centripetal river pattern
The following are hints to follow when you describe drainage in topographical map
Divide the map into drainage basins using compass directions. Note that the drainage basin is an area drained by single river system.
In each drainage basin explain the drainage pattern which the river system in the basin take. The common river drainage pattern are
For each drainage basin explain how the rivers drain the relief region i.e highlands, lowlands and plateaus. at this part state the direction of the flow of the river, where the river is pouring its water and whether the area is well drained or not. The area is well drained when there is no swamps or marshlands and is not well drained when is waterlogged areas.
HOW TO DESCRIBE VEGETATION DISTRIBUTION IN TOPOGRAPHICAL MAP
Vegetation is the collective name for plants in particular area. it can be natural (man have not planted them) or artificial(planted by man)
The natural vegetation can be categorized into
Forest
In the topographic map, the distribution of natural vegetation is shown by conventional symbols. This means they are all listed on the map key.
The following are hints on how to describe vegetation in topographic map
first, categorize or group the type of vegetation as shown in the map. So this means that you have to look in map key to see symbols representing vegetation after that yo will look into the map and state what type of vegetation you have found. For example if you see forest and woodland in your map then state that in the map provided vegetation consist of forest and woodland
Secondly, give brief explanation to vegetation distribution. This means you have to state using direction, place names or any other methods of locating place on map the location of each type of vegetation you identified earlier.
This is how to do map enlargement and map reduction
IN REDUCING ANY MAP TO GIVEN SIZE, THE FOLLOWING STEPS SHOULD BE FOLLOWED:
- Measure the length and width of the map.
- Divide the length and width by 2 or 4 if you are asked to reduced the map to half or a fourth of its original size. For example, if the length and width of a map are 24cm and 20cm respectively, such a map should measure 12cm by 10cm if seduced to half its size and 6cm by 5cm if reduced to a fourth of its size and so on.
- Having reduced the original map, it is obvious that the scale would equally change. Therefore, if a map has a scale of 1:50,000, the scale of the map changes to 1:100,000 if the size has been reduced to half, and 1:200,000 if the size of the map has been reduced to a fourth of its original size.
- The features to be shown on the reduced map should also be proportional to the required size of the map.
- When you have finished drawing the reduced map, remember to write its title and the new horizontal scale.
IN ENLARGING ANY MAP THE FOLLOWING STEPS SHOULD BE TAKEN
- Measure the length and width of the original map.
- Multiply the length and width by 2 or 4 respectively if you intend to enlarge the map to twice or thrice its original size.For example, if the length and width of a map are 5cm and 3cm respectively, such a map would measure 10cm by 6cm if enlarged to twice its size and 20cm by 12cm if enlarged four times its size and so on.
- Having enlarged the original map, it is equally obvious that the scale would change. Therefore, if a map has a scale of 1:60,000, the scale of the map changes to 1:30,000 if the size has been enlarged twice and 1:15,000 if the size of the map has been enlarged to four times its original size.
- The features to be shown on the enlarged map should also be proportional to the required size of the map.
- When you have finished drawing the enlarged map, write its title and the new horizontal scale.
HOW TO DRAW CROSS SECTION FROM TOPOGRAPHICAL MAP
A cross-section is a profile of the area under discussion. It is a diagram showing change in height along a line drawn between 2 points on a map.
In an exam, the vertical scale will always be indicated – you must not change it. e.g. 1 cm represent 50 metres on the Y axis (vertical axis) Remember: the Horizontal Scale remains 1:50 000 (this will be map scale)
Procedure for drawing cross-sections BEFORE starting, study the area of the cross-section to the general shape or lie of the land, that is always have an idea of the shape BEFORE you begin plotting heights or drawing the section.
Join the 2 points, making sure the FROM point is on the left.
On a “magic” piece of paper, delimit the cross-section on the map and match it to the “given” graph. Mark off the right hand extreme on the graph and draw a vertical line to delimit it.
On the map, place the piece of paper, and (holding it steady) mark off EVERY contour that cuts it, ACCURATELY numbering each mark vertically. Eg. 2 2 2 2 0 2 4 6 0 0 0 0
Now place the “magic” piece of paper along the base line of the graph – ensure that the 2 extremes are accurately lined up. Matching the vertical scale to the marked contour height, mark a small “x” to show the position of each contour on the graph.
YOUR EDGES OF THE GRAPH MUST COINCIDE WITH THE LIMITS OF THE GRAPH – nowhere on earth does a piece of land end in mid air!!!
Join these points free hand, taking care to show valleys or hills where 2 or 3 adjacent points are at the same height.
Write a FULL heading on your cross-section eg. Cross section from • 96 to r 281 on 3326 BC Grahams town map extract 1 : 50 000 Topographical Series
Mark in the horizontal scale ,Mark in the vertical scale showing the units of measurement Label the edges of the cross-section using the designated points (NOT just A and B
Vertical Exaggeration This is used as the vertical scale must be exaggerated because, if the horizontal scale were used for the vertical, the relief would show as an almost flat line on a cross-section. Formula:
Vertical Exaggeration = Vertical Scale (Given on the cross-section)/Horizontal Scale (1cm represent 50000cm)
Eg Vertical Scale = 1 cm represent 20 metres Convert to cms (an RF) by multiplying by 100 i.e. 1 : 2 000 VE = 1:2000/1:50000 VE=50000/2000/ VE = 25 times
Inter visibility This is the concept of whether one place on a map can be seen from another. It is decided upon by studying the heights between the 2 places. Any ground which cannot be seen behind a higher height is known as DEAD GROUND.
If a convex slope is between the 2 places, the second cannot be seen. A rough cross-section sketch shows this more easily. Intervisibility can also be affected by presence of buildings or vegetation.
The following are procedures to be followed when drawing a sketch map from a given photograph:
Draw a rectangle or square of the same size as the photograph on the piece of paper. This forms a margin of the map
Subdivide the photograph to be sketched into three equal section using faint pencil line to get foreground, middle-ground and background
Draw faint vertical lines on the photograph with the same distance apart as the horizontal lines to form squares. this forms left, center and right section
Starting with the background draw the skyline on your frame work as it appear in the photograph.
Fill in just the main features in the background using clear single line
Sketch all important details on the middle and foreground in your framework.
Complete by lebelling all important features such as vegetation, prominent building, transport and communication as well as land use.
Give the sketch a suitable title.
Draw the sketch in pencil so you can easily erase or alter any mistakes. Only color the sketch map if you have spare time remaining following the completion of all other sections
3 CONCEPTS OF NORTH IN MAP READING
North is geographically defined as a zero degree bearing. In geography there are three types of north
True north
This is the position of the geographical north pole. all longitudes meets at true north. It is usually represented by a star on the sign of the topographical map
Magnetic north
This is the direction to the magnetic north pole, as shown by the north-seeking needle of a compass.
When a needle of a compass is left to swing freely, it comes to rest in a north-south position.
Its north point shows the earth's magnetic north. This type of north varies from place to place and from time to time.
It is usually represented by a line ending with half of the arrowhead
Grid north
On most topographical maps, there are lines that are drawn north to south. These lines are called grid lines (eastings). they meet at point in the north pole called grid north. It is symbolized by the latter GN.
Comments
Post a Comment