MAP WORK
What is map?
A map: is the representation of the parts of the earth’s surface on a flat material such as a piece of paper, wall, clothes and a piece of wood.
Map interpretation is the ability to translate the symbols and signs on the map and the real features that they represent on the earth surface.
MAIN TYPES OF MAPS
1. Topographical maps: Are maps which shows both natural and man made features. Example: which are natural features e.g. mountains, valleys, hills etc. and manmade features. Example: bridges, ponds, roads, settlements etc.
2. Statistical maps: Are maps which show the distribution of things in quantitative manner e.g. distribution of rainfall, temperature, crops etc. Examples of statistical maps are dot maps, Isopleths maps, isoline maps etc.
OTHER TYPES OF MAPS
1. Large scale maps: Are those maps drawn to large scale size e.g. 1:10000. These maps gives a larger representation of small area, they are also more detailed (shows a lot of information). They represent areas like cities, towns and villages.
2. Medium scale maps: Are those maps drawn to medium scale size e.g. 1:100000. They show a moderate amount of details. They represent areas like districts, regions and countries.
3. Small scale maps: Are those maps drawn to small scale size e.g. 1:50000. They give a small presentation of a large area; they show little content (little information). They represent areas like continents and the world.
CONTENTS OF THE MAP
Contents of the map: Are the information which are shown on the map which can either natural, artificial or supportive contents.
TYPES OF MAP CONTENTS
i. Natural contents.
ii. Artificial/man-made contents.
iii. Supportive contents.
A. NATURAL CONTENTS/INFORMATIONS/FEATURES
Contents/features: Are those natural informations found on the natural environment which are not influnced by man.
Example natural contents/informations
i. Relief features or landforms (mountain, hills, vallyes, saddles, basin, slopes, depressions).
ii. Vegetation (forests, bamboos, thickets, scrubs).
iii. Water bodies (lakes, rivers, seasonal swamps, ocean dams, etc).
iv. land surface.
A. RTIFICIAL FETURES/CONTENTS
Artificial or man-made features: Are those features or informations which are found on the map as result of manade.
Example of artificial features
i. Roads.
ii. Railways.
iii. Settlements.
iv. Crops like tea, coffee, cotton, sisal, etc.
v. Bridge
C. SUPPORTIVE CONTENTS/BASIC ELEMENTS OF A GOOD TOPOGRAPHIC
MAP/ESSENTALS OF THE MAP/MARGINAL INFORMATION OF THE MAP
Map supportive contents: Are essentials of the map which guide the map users to use the map in a proper way.
The basic skills required in understanding how to read a map include;
1. Tittle: it helps to identify the place where the map was produced. E. Arusha sheet, Korogwe sheet.
2. Scale: is the ratio between the map distance and the actual ground distance e.g. 1:50000
3. Key/ legend: it used to identify the various signs and symbols used on the map.
4. North direction: It used to locate the direction of place on the map.
5. Margin/Frame:This is the frame which used to show the boundary of the map.
6. Date of compilation: This used to indicate the time when the map was produced. Example 1986.
7. Publisher name: It used to show the name of institution or organization published the given map. Example: The ministry of land in Tanzania.
FACTORS THAT AFFECT/ DETERMINE THE CONTENTS OF THE TOPOGRAPHICAL MAP
1. Purpose of a map/cartographer: Normally the appearence of difference features on the map is largely depends on the purpose of the cartographer. Aim of the cartographer determines what to be shown on a map since map is selective.
2. Scale size of the map: Maps are drawn to different scale sizes depending on the size of the land to be represented. it has to be noted that scale size of a map is about contents to be shown on a map. thus if there are two maps of the same area of land but drawn by the different scales sizes they are likely to differ in contents.
3. Date/time of compilation/production: Normally map is likely to show information which was represent by the time when it was prepared. Therefore two maps produced at different time at the same place are likely to be differ in terms of their contents because the landforms and other features are dynamic in nature.
4. Different in environment: A map shows what is found at a given place and not otherwise therefore maps of different places are likely to be differ in terms of their contents.
5. The nationality of the cartographer: The map produce by the foreigner or indigenous cartographer are likely to differ in contents. The foreigner cartographer might not include same contents because of being not familiar with the area.
THE MAP SCALE
Scale: is a ratio between the map distance and the ground distance. E.g 1:50000. TYPES OF SCALES
Scales are classified according to their size.
i. Small scales
ii. Medium scales
iii. Large scales
1. SMALL SCALE
Are those scales that cover large area.
i. It represented by small measurement on ground.
ii. It. It show small size features.
iii. They consist many contents.
Iv. The map scale range from 1:250,000 to 1:1000, 000.
2. MEDIUM SCALE MAP
These are scales which rage between the large and small scale.
i. It represent relative large area. example villages, districts or town.
ii. They shows moderates contents.
iii. The map scale range from 1:50,000 to 1:250,000.
3. LARGE SCALE MAP
These are scales that cover a small area such as village, school, streets etc.
i. They represents very few features.
ii. They are used to represents small ground areas.
iii. The map content is enlarged and they are clearly seen.
iv. The map scale range from 1:5000 to 1:25000.
METHODS USED TO EXPRESS SCALE
There are three types of methods used to express of scales
i. Statements scale
ii. Representative Fraction (RF) scale.
iii. Linear (graphic) scale.
1. STATEMENT SCALE
Statement: is the method of expressing scale by usin words or verbs. E.g. one centimeter on the map represents ten kilometer on the ground. This can also be expressed in short as 1cm represents 4km or 1cm to 4km.
2. REPRESENTATIVES FRACTION (RF) SCALES
Representative fraction scale: is the method of expressing scale by using ratio and fraction (e.g. 1/50,000 fraction) or ratio (e.g. 1: 50, 000 ratio).
Therefore,
3. LINEAR (GRAPHIC) SCALES
linear or graphic scale: is the method of expressing scale by using which is subdivided into smaller equal units. There are two kinds of linear scales: the short line scale and the long line scale.
i. A short line scale: it consist a single short line that represents the actual ground distance. To get the unit of measurement on the map, one has to measure the length of
the line in centimeter. E.g
ii. A long line scale: it consists of a long line that is divided into several equal parts. It has two sections. The linear scale is divided in to two parts which are
a). Primary scale: it located to the right hand side of the graph which is expressed in Kilometers (KM).
b). Secondary scale: it located to the left hand side of the graph which is expressed in Meters (M).
Secondary section primary section
SCALE CONVERSION
Scale conversion: is the technique of changing map scale from one form of expression scale into another. Normally the cases include the following:-
1. Conversion of Representatives scales (R.F) into statement scale.
Example: Given a Representatives fraction scale of 1:50,000 convert it into a statement scale.
Solution
Therefore 1cm on the map represents 0.5km on the ground.
2. Conversion of statement scale into representative’s scale.
Example: Given that a statement scale of 1cm represents 0.5km, convert it into representative’s fraction (RF) scale
Solution
3. Conversion of statement scale into linear (graphic) scale.
Example: Given that a statement scale of 1cm represents 0.5km, convert it into linear (graphic) scale.
Solution
IMPORTANCE OF MAP SCALES
1. It help to determine the relationship between the map distance and the actual ground distance.
2. It used to calculate distance.
3. It used in measurement of area.
4. It used in land use planning.
5. Scale is used to calculate gradient and vertical exaggeration.
METHODS USED TO LOCATE THE POSITION OF THE PLACE ON THE MAP
1. The place name: This is method use the specific names of physical features on the map to indicate their direction. E.g, Arusha, Tanga.
2. Latitude and longitudes: these are lines drawn on the map which ecpressed by degree, minutes and seconds to measure the durevtion of the place. However latitude are horizontal line running from west to south on the map while longitudes are vertical lines. E.g 0-5N/S, 5-15N/S, 15-30N/S.
3. Grid system numbers: Are numbers which show the position of physical features, most large scale topographical maps having vertical and horizontal lines drawn on them. Grid lines are drawn for the specific purpose of facilitating map reading especially fixing positions on the map. Vertical lines are called Eastings; they are numbered towards the east. Horizontal lines are called Northings. They are numbered towards the north.
5. North direction
Direction: is method of locating the position of the place by using cardenal points.
Direction on the map can be given in four, eight or sixteen cardinal points of compass and their corresponding bearings.
6. The compass bearing
Bearing: is the degree angle of an observation the line connecting two points on the map with reflection to an area on the earth’s surface measured clockwise from north direction. The method is mostly used to establish the location of a place from another place by giving the degree angle measured clockwise from north.
PROCEDURES FOR DETERMINING BEARING
i. Identify the two recommended points on the map by considering the grid reference or place names given. Sometimes both grid reference and place names can be provided together.
ii. A straight line has to be drawn to join the end points on the map. The line represents an observation sight between the two places in a mapped area on the earth’s surface represented.
iii. Establish the four cardinal points at the point of observer. The establishment of the cardinal points should take into consideration of the north direction indicated on the map.
iv. Take the protector and measure the angle of an observation line that connects the two points clockwise from north direction.
v. Read the angle in three numbers. Example 0900
EXAMPLE
Determine the bearing of point B from point A
Types of bearing
i. Back bearing: is the bearing which measured from the object to the observer.
ii. Foward bearing: is the bearing which measured from the observer to the object.
Rules/ procedures of calculating back bearing BB = FB + 1800 if less than 1800
BB = FB – 1800 if the FB is greater than 1800
NB: The procedures of finding the direction are the same to those procedures of finding the bearing, instead of write the number of angle (bearing), here we write only direction such as North, South, West etc. of a given point.
TREND AND ALIGNMENT OF ELONGATED OBJECT
Alignment: is defined as a general direction of elongeted on the map and the earth’s surface. while trend: refers to the bearing of an object.
The elongated object can be like that of a road, railway, ridge and others of the same nature.
Alignment is best described by starting both direction and bearing. Example: the road align from 450(NE) to 2250(SW).
PROCEDURES INVOLVED IN FINDING THE ALIGNMENT
i. Identification of the two end points on the topographical map given. The end points can be identified by taking into consideration of the grid reference or place names given.
ii. Drawing the straight line using a ruler and pencil to join the two end points.
iii. At the central point of the drawn like mark the four cardinal points.
iii. Take a protector and measure both degree angles in which the drawn straight line trends.
iv. Write the alignment starting with bearing followed with direction.
Consider the following case N
That is- the top number (numerator) represents the map distance on the ground and is SYMBOLS AND SIGNS
2). QUANTITATIVE INFORMATION ON MAPS
A) MEASURING DISTANCE ON THE MAP
Distance: is the length between two points on the earth’s surface. How to measure distance.
In order to obtain distance of any feature on the map, consideration should be made on whether the distance to be measured is straight or curved.
1. Straight distance: For all straight distances a ruler is used to obtain the distance directly from the topographical map given.
2. Curved distance: It becomes difficult to obtain curved distance of the features by the use of a ruler directly from the topographical map when the area is inclined. In this case the following devices can be used:-
1. A pair of divider: A pair of divider is commonly used to measure the distance. You should start by breaking the length by using a pair of dividers then transfer some of the already drawn straight lines. Then transfer the measured line to the linear scale or ruler for calculation to get the actual distance.
2. A piece of a string: Slowly measure the distance by a piece of string along a given length then transfer it to a linear scale or ruler for actual calculation of the distance.
Actual distance
½ km ½ x 2 = 240km
1:50000
1/50000 =20cm
100000 = 20cm
50000 x
=10km.
A piece of strip paper
Slowly lay a piece of paper along a given length then break your lengths into short segments then transfer to the linear scale for measuring and calculation.
MEASURING AREAS ON A MAP/CALCULATE AREA OF REGULAR IRREGULAR
Area: refers to the bigness or smallness of an area on the earth’s surface. Normally the area to be measured include,
i. Area of regular shape
ii. Area of irregular shape.
1. REGULAR SHAPE
Regular shape: These are areas with definite shapes such as squares, triangles etc. Their total perimeters or areas are obtained by mathematical formula i.e. length x width, side x side etc.
2. IRREGULAR SHAPE
These are areas with indefinite shapes such as lakes, farms, ponds etc where these areas can be obtained by any of the following three methods.
(a). Square / grid method b). Strip / division method.
c) Geometrical/ composite method
1. SQUARE METHOD
Square method: This is the most accurate and most method used in many topographical maps.
Square methods are normally used as follows;
a) Count all full squares that are complete
b) Count incomplete squares and divide them by 2
c) Add them with the full squares to obtain the total area in km2.
Example:
METHODS USED TO SHOW OR LOCATE POSITIONS OF A PLACE ON A MAP
The following are major methods used to show positions of a place on a map.
i) Grid reference.
ii) Place name
iii) Bearing.
Iv. compass direction.
v). Latitude and longitude.
1. Place name: You can locate the position of a place by where the features are found i.e. Mbeya, Dodoma, Mtwara.
2. Grid reference: Grid reference is a network of vertical lines and horizontal lines on a map. Vertical lines whose numbers increases towards the east are called easting. Horizontal lines whose numbers increase towards the north is known as Northings.
Where horizontal lines and vertical lines meet or cross each other they form a square known as grid square. (G.S). A grid reference point is written inform of six digits starting with three digits of Eastings then three digits of nothings’
To write down the grid reference of point A, B, C, D. A=12006
B =130065
C =140067 D=14003.
3. COMPASS DIRECTION.
Compass direction is divided into
a) 4 cardinal points
b) 8 cardinal points
c) 16 cardinal points
HOW TO FIND DIRECTION OF A PLACE ON A MAP.
1. Identify them due to points on the given map. Points may be given by using grid reference points, place name or letter.
2. Draw a straight line connecting the two points
3. Mark the major four cardinal points at the starting point with the word from.
4. Now look at the question asked then provide your answer.
4. COMPASS BEARING
Bearing: is the measurement which measured in degrees clockwise from north. They are written in three figures i.e. 0900, 0450
HOW TO FIND BEARING ON THE MAP
1. Identify the grid reference points given on the maps.
2. Draw a straight line connecting the two points
3. Draw the major four cardinal lines at the starting
4. Now look at the question asked use a protector to measure degree clockwise from north up to the line joining the two points. Provide your answer in degrees i.e. what is the bearing of point A from B
Ty pes of bearing
a). Forward bearing
b). Backward bearing
1. Forward bearing: Is the bearing which measured from the observer to a object.
Procedures to calculate forward bearing
i. Identify the two points.
ii. Join them with a straight lines.
iii. Draw north direction on a second point.
iv. Measure the angle by using a protector.
v. State the bearing in terms of degrees of the direction.
i.e. Find the formed bearing of Moa from Midland.
B=1350 SE
Find the bearing of Mbezi to Ubungo.
The bearing of Mbezi to Ubungo is 1350 SE
b) Backward bearing: Is the bearing which measured from the object to the observer.
How to determine the back bearing
1. Find forward bearing.
2. Mark the cardinal point north direction of the opposite point
3. Find the bearing of the observer along the straight line principally to determine the back bearing= FB +OR- 1800 BB= FB +1800 IF FB<1800BB=FB-180+FB>1800
IMPORTANCE/USEFULNESS OF MAPS
1. It helps pilots to reach the directions
2. It used to describe the features of the earth.
3. It used in land use planning. E.g road construction.
4. it used to show various human activities on the earth surface.
5. Maps are used in military activities.
6. Maps are used to show the distribution of geographical informations e.g climate, vegetation, etc.
7. Maps are used to show the settlement pattern.
GUIDING QUESTIONS
1. With evidences from the map describe three contents found on the map.
2. Outline five map supportive content/marginal informations found on this map.
3. By giving evidences in three points decribe factors which makes this map to be unique from other maps?
4. By giving evidence outline four factors which distinguish this map from other topographical maps.
