Understanding Practical Geography: Map Work - Surveying - Field Work - Research
Practical Geography for Secondary and Tertiary Students
Research Paper (undergraduate) 2011 58 Pages
TABLE OF CONTENTS
PART ONE: SURVEYING
Chapter one: History of surveying
Surveying today, what surveying is?
Major Elements of survey, Branches of surveying Units of Measurements, Purposes of surveying
Chapter two: Chain/Tape surveying
Meaning, Equipments used, The Fieldwork of chain surveying Obstacles in chain survey, Booking, Plotting
Errors in chain surveying, Activity
Chapter three: Prismatic Compass Survey
Meaning, Merits and Demerits
Methods used, Bearing, Intersection, Resection
Types of Prismatic Compass, Open traverse, Closed traverse. Application of traversing, Reduction of Error in compass
Chapter Four: Plane tabling
Meaning, Equipment used, Merits and Demerits, Alidade.
Chapter five: Leveling technique
Meaning/Definition, Purposes, Equipments, Terminologies used Methods, Rise and fall, Height of Collimation
Activity, Types of levels, Basic theory, Application Errors in leveling
PART TWO: FIELD WORK
Charter one: Fieldwork
Meaning, Importance, Objectives
Organization of fieldwork/Project work Report writing, Activity
To my Lord and Redeemer: you directed and guided me throughout this process and hope you will do so the upcoming work in all my life in this precious world you endowed to us. To the reader of this book, you deserve thanks since you are the one who forced me to prepare and finally compose this book. Let this teaching manual be for our own benefit. This book belongs to those who possess the so called last resort “teachers and teacher trainees” to you I ought to say you will enjoy your life through directing the society in the right way, let do our talented profession instead of thinking to change the mind.
To my Geography Students at Umoja Teaching Centre-Mwanza Cit,y Tanzania And
To my friends and all the people of United Republic of Tanzania
PART ONE: SURVEYING ۩۩CHAPTER ONE ۩۩
HISTORY OF SURVEYING
On the early age of discovery, ancient people were living on curve and later on, in town and city. You can hear somebody say ‘I was born and grown up in this town or city’ this is normal in our daily life because between and among us is usual to be found in different residential area at a village, sub-town, town, or in city. All these are fabricated environment whereby individual human beings are closely related with. Now what is a city? It can be explained as a well-surveyed and planned livelihood area, which involves well-established political, economical, cultural and social amenities.
Early history of surveying brought up to the history of Moses who wrote the book of Deuteronomy “Thou shall not remove thy neighbor’s landmark, which they of old time have set in thine inheritance, which thou shall inherit in the land that the LORD thy God give thee to posses it.” It is the time where Israel’s were thinking on how to change the boundaries of the city. (Deuteronomy 19:14).
About 200BC, Eratosthenes and associates (others) computed the dimensions of the earth (shape and size).During that age it was purposely for studying the shape and size of the earth. 120 BC Greeks developed the science of geometry and were using it for precise land division, on that time they advanced their technology as DIOPTER. They were standardized procedures for conducting surveys.
14BC, the Egyptians first used it to divide land accurately into plots for the purpose of taxation and easy approximation of distribution of land (plots). During rainy seasons was a problem to determine the boundaries, because of floods. After floods of Nile River, surveyors in Egypt were able to replace the boundaries.
1800 A.D, It was the beginning of industrial revolution whereby people were looking for favorable environment(s) for construction of industries. The importance of exact boundaries and demand for public improvement of infrastructure) railroad (TAZARA), canals (Suez), roads, bridges (Slender bridge), telephone poles, electric poles) brought surveying into a prominent position. As the history of surveying is concern, instruments that are more accurate were developed, such as science of Geodetic and plane surveying and leveling technique.
Surveying has been essential elements in the development of man’s environment for so many centuries. It is important in planning and execution of nearly every form of construction. The process of surveying involves measuring and recording; measuring and recording distances, angles, height and size of the earth surface features and drawing them on plan, section or map.
Nowadays surveying affects most everything in our daily lives. A few of the areas where surveying is being used are: to map the earth above and below the sea, prepare navigational map (land, air, sea), establish databases for natural resources managements, development of engineering data for huge buildings constructions, land development (settlements), roads, railways, bridge constructions and so forth.
WHAT SURVEYING IS
This is the science of measuring and recording distances, angles, heights and sizes on the earth’s surface to obtain data from which accurate plans and maps is made. The art and science (systematic process) of determining the position of natural and artificial features on, above the earth’s surface or establishing such point; and representing this information on paper plans, as figures, tables or computer based map. (Measure related positions and present them numerically and or graphically).
It is the measurement of dimensional relationships as of horizontal distances, elevations, directions and angles on the earth’s surface especially for use in locating property boundaries, construction layout, and map making. Also is a technique of measuring to determine the position of points or of making out points and boundaries. Generally, surveying is the systematic process of making measurements on the field from which maps are drawn. The map is the most essential piece of equipment which the geographer, engineer and architect uses, and their training is said to be incomplete without instruction on procedures of map making where surveying is most important. The geographer must learn to read, make and use map as an essential element on their carrier, in so doing he/she will be well equipped in geographical world.
THE MAJOR ELEMENTS OF SURVEYING
Surveying like other field of study has its own elements. There are four major elements of surveying. These elements are also known as methods of conducting surveying. In other
textbook, these elements are termed as types of surveying cartographers).
(a) Chain or tape surveying
(b) Prismatic compass survey
(c) Plane table surveying
(d) Leveling technique
BRANCHES OF SURVEYING
(i.e. geographers and
Surveys can be classified into two main branches as Geodetic and Plane.
- GEODETIC SURVEYING
This is a branch of surveying which takes into account the theoretical shape of the earth (curvature of the earth). Generally has high in accuracy, and cover large areas (greater than 300 square mil). It is deal with large distances measurements on the earth surface. It aimed to establish a network of horizontal and vertical monuments that serves as a reference framework for initiating other surveys and research, always goes beyond the smaller horizontal and vertical measurements of distances, angles, sizes as well as latitude and longitude, it is carried out at National level and often involves international cooperation.
- PLANE SURVEYING
This is a branch of surveying which assumes that the survey area is a flat plane. It neglects the curvature of the earth. The area measured is considered as being plane. The surface of the earth is projected onto horizontal planes that form tangent plane to the surface at the point from where the measurements are taken. It can be used only for base maps covering small areas. For example school, villages and township. The area covered generally is less than 300 square millimeters. It is a common method used in surveying.
In practice manner, surveying is classified on a number of ways depending on uses and purposes of the expected results (map). Some authors/scholars classified surveying into three categories as follows:-
- Land /astronomical/marine/cadastral/and topographical surveys
These are types of surveying based on the nature of the field of survey. Land survey is used to fix boundaries and finding out the areas of ground. In Tanzania for instance the boundaries and division of public lands for difference purposes such as settlement, industrial areas, bus terminals and playing grounds has been fixed by government. It is also known as original survey because it relies on establishment of corners/markers on unsurveyed areas or retracement (recover previously established boundary lines). Topographical survey is aimed to determine locations for natural and artificial features and elevations used in map making (this survey results on topographical map).
- Engineering/military/route and geological survey
All these are classified according to the object of survey, which involves construction survey, or hydrographic survey. It conducted where buildings, bridges, roads, canal and other structures are to be built. It provides locations of structures and information on various elevations of structures. It involves nautical or hydrographic survey that is used to establish shorelines, boundaries of lakes, streams and other water bodies.
- Aerial/photogram metric survey
These types of survey are used to determine distances on he ground by means of photograph taken from airplanes. This kind of surveying is used for recording information quickly on a large area and makes measurements. It almost used for topographic mapping of large areas.
Another crucial classification is based on instruments used in surveying, Geographers are interested on this kind of classification, and they argue that surveying are classified into four major types as far as the information required in map making is concerned. These are chain, plane table, prismatic compass and leveling. In this book, different types of surveying are discussed in details in order to make students familiar with concepts of surveying to enable smooth understanding of most advanced concepts of surveying.
UNITS OF MEASUREMENTS
We need to notice that the process of surveying involves measuring and recording distances, angles, (magnetic compass, sextant, theodolite) and height of the earth surface. It is very important to determine the units used in measurements and below are among of those units used and described as follow:-
- Horizontal Measurements
SI-units (metric system) are used (Km, m, and mm) in few cases, English Foot System can be used (Miles, feet and inches). For example 1ft = 0.3048m; 1km = 0.62131miles; 1hectare = 2.471acres; 1km2 = 1,000,000m2 ; 1km2 = 100hectare = 100 (ha).
- Angular Measurements
Are angles between baselines or reference directions and survey lines or objects to be fixed out Degrees are usually used but in few cases- gradians/gons are used.
For Degrees: 1Revolution = 3600, 1Degree = 60’; 1Minute = 60’; 1Minute 60" seconds. For Gons: 1Revolution = 400gons; 1gon = 100mgon; 400gons = 3600 =2Л radians.
illustration not visible in this excerpt
- Angles are measured in degrees (00 ).
- A right angle is 900 in a sexagesimal system.
- Linear or Horizontal measurements are distances between points on the land ( ground) recorded in metres .Equipment used to measures are chains, tapes, steel band ,optical methods, electronics methods. Angular measurements are measured through magnetic compass, theodolites and levels
PURPOSES OF SURVEYING
Broadly speaking, surveying is purposely for map making or plan over a certain area/place, showing the existing situation of the area for development It also required in planning. For example planning of village settlements, town planning (rural and urban planning) Communication purposes for example construction of railroad, road, telephone lines and electric lines. Location of physical and non - physical features on the land, either surface. For example farms, forest, football pitch, villages etc. adding details to the existing map or large- scale map.
۩۩ Chapter Two ۩۩
CHAIN / TAPE SURVEY
Surveying is the making of measurement in the field from which maps are drawn. The map is the most essential piece of equipment that geographer, pilot and planner use. The method is the method of surveying in which only linear measurements are taken in the field. Its principle is built upon the framework of triangles. It aimed to measure a series of straight lines on the ground with a chain or tape. It is the simplest method and common of making linear or horizontal measurements for small area. The process involves fixing of two relatively measured lines called tie (ties) or by right angles (off - sets) (90˚).
Chaining (with chains) is the process of the direct measurement of a line, although it is not necessarily with a chain. The main types of chain that are used for chaining are the Gunter’s chain, The Engineer’s chain and the metric chain. Chaining is the process of measuring distance using chains with the help of ranging poles, pins and other gears.
GEAR/EQUPMENT DESCRIPTION AND USE
The main equipment used in chain or tape survey are the chain or tape, arrows, ranging poles, a measuring rod, a cross staff, Pegs to mention a few.
CHAIN OR TAPE
There are various types of chain such as metric, Günter’s, Surveyors, engineer, revenue chain, and steel band chains. The chain or tape is used for running chain lines, made of tempered steel wire links connected by rings. Gutter’s chain is 66 feet long is also used and is divided into 10links and each 0.66 feet or 7.92 inches long. The metric chain is also used. It is usually 20m long and is divided in 100 links each 200 millimeters long. A metric links is always 200mm long a 30m chain will therefore contain 150 links. The end of the chains are provided with brass handle at each end with swivel joint that can be turned without twisting.
Steel tapes are also used in measurement of distances. The brass handle at the end of the steel tape or chain is included in the measurement. Steel chain and tapes should be handled with the utmost care. It should be wiped with a very slightly oily rag after use. It should be wiped with a very slightly oily rag after use. Steel tapes can be easily cut the palm so handle with care. Tit is preferred for short distances.
Arrows are pointed metal markers, which can be stuck into the ground. They are about 36cm long and are bent at the end to make a circle to which rag or cloth can be tied to make them easier seen. They are used to mark chain lengths. They are used to mark chain length. They are thin skewers for marking points on land.
Ranging poles, at times referred rods are poles of circular section about 25mm in diameter and 2m long. Nevertheless, those that are graduated in the imperial system have heights ranging from 6ft to 10 feet. They have pointed ends, which are steel shed for pushing in the ground. They are painted red, black and white in bands each 500mm wide so that when they are used to make sections they can be easily seen at a distance. The method of placing ranging poles on a straight line between two points is known as ranging. It made of poles of wood or light metal. Sharpen on the end for driving in the ground.
Cross staff is made up of metal or wood with eye slits at right angles, it is used for marking angles, and used to measure right angles from the line of traverse. This instrument allows a right angle to be set out with reasonable accuracy. The head of a cross staff is mounted on a shortened version of a ranging pole and comprised a cross with vertical end members in each of which is a slits it can be easily improvised.
Note book: Note book is used to record all data collected in the field .it should be good and quality book of about 150mm by 100mm.
Spiral- bound notebook is recommended. It is a good instrument for keeping record during survey.
Pencil: A good pencil that is sharp is needed for writing and drawing some strategic during survey
THE FIELD WORK OF CHAIN SURVEY
This is the preliminary inspection or investigation that the surveyors should conduct before the actual survey work and surveyor should work over the entire area to be surveyed in order to obtain real picture in his/her mind of the whole area to be surveyed. Moreover, this enable to decide the most suitable way of carrying out the work economically in time and labor any map or plan covering the area to be surveyed is a useful aid during this preliminary inspection while carrying out reconnaissance or preliminary survey. The surveyor will prepare a sketch planning showing lines chosen to form the framework of the survey.
The term also can be defined as the process where by the surveyor become familiar with a site to be surveyed by working around taking the area (overview) view and noting down the dominating features sketch map of the area should be produced and the outer boundaries of the area are noted. It is conducted purposeful for militally, construction purposes, extraction of minerals and other activities recommended.
- NORTH POINT
During survey the north point, (north-south) line must be obtained with the help of the compass and marked on the ground or by measuring the bearing of the chain lines by compass and working out the north- south line from it.
- CHOICE OF STATION
During the preliminary inspection, the following point must be born in mind as the criteria to improve / provide the best arrangement of survey lines:-
1. The number of survey lines should be as few as possible but the must be sufficiency for the survey to be supported.
2. If possible, a long line should positioned part across the site to form a base on which to build the triangles.
3. The triangles to be used should be well conducted no triangles should contain an angle which is less than 30 or greater 150.the angles used for plotting should intersect as close to 90 as possible so as to provide a sharp definition of the station point.
4. Every part of the survey should be provided with check lines. If in a triangle we measure a forth line from a know point from a one side of the triangle to a known point of a second side. Important thing to note is that you can see if the measurement first the triangle when it plotted; if it does we know that our work is correct if it does not we know that our work is a mistake somewhere It is convenient in chain survey to call such lines “check lines” while the ordinary lines dividing; the areas triangles may be called “tie lines” both lines may be used to serve as survey lines from which to measure details by offsets at right angles to the lines.
5. Whenever obstacles occur in course of the surveying proper measures, such as describing under chaining round obstacles must be employed to overcome them. In steep slopes also constitute need to employ the technique of step chaining.
6. Short offset line should kept close to the feature to be offset, ideally within 2 meters so that an offset measuring rod operated by one person can be used instead of tape which need to people.
7. It is usually convenient to position a station on the extension of a check line or on the side of the triangle. Such points can be plotted without the need for intersecting arcs.
- RUNNING THE CHAIN LINES
In chain or tape surveying, each line is measured by two people this are leader and follower. The survey team mail consist major three people (the leader who is leading chairperson. The follower and the booker or surveyor) the leader commercials from the beginning of the line holding the front end of the chain and taking along the number of arrows. When the chain is full extended as he walk towards the end of the line, the follower behind the starting point signals to the leaders “right” or “left” until the end of the chain is in a direct line with the far station. The follower says, “Right” or “down” and the leader places his end of the chain of the groups and puts in the arrow at the exact point.
The chain remains on the ground while the offset and the booking parties do their work [booking is the process of entering measurement in the field book, rule and pencil or notebook by using ordinally exercise book start from the bottom of the page and as you go around the chain line, you walk upward] after which the leader take his hand to the chain on stage further along the line and the followers comes up to the arrow. The same process is followed until the line is completed.
As the leader goes along the followers shoes how many complete chain length have been measured.
- MEASUREMENT OF OFFSETS (RIGHT- ANGLES)
At times the boundaries of the areas to be surveyed may be irregular. The method of surveyed such areas with irregular with the irregular boundaries is first to lay down a network of triangles which can be plotted and checked from this survey lines, offsets are measured. The offset are perpendicular measurement from the chain lines to the point of detail. The line of traverse and surveying in an area until the shortest distance on the line of traverse is obtained.
In measuring offsets perpendicular lines may obtained in one of the following ways -:
a. CROSS STAFF. Through judging with eyes right- angle formed between two tapes.
b. By showing an offset to obtain the shortest measurement (ARC BISET), Tape is fixed at the point outside.
In dealing with offset, the features to be surveyed may take three forms and the procedure for each is described below:-
Irregular feature such as hedge lines or bank of streams
In chain survey such features are regarded as being divided into a series of straight lines and offset are taken to each point of change of direction which are large enough to show up the drawings need to be measured loess offsets are headed for surveying vague outlines, such as the age of scrub land and marshy ground than a role definite but still irregular boundary such as hedge.
Straight features such as wall and fences
In dealing with such features only the ends of the straights, need to be offset in order to check the straight the end should be tied. Surveyor should back to chain by the measurement from the feature to another point of the chain line. Another way in round is that at least two other offset should be taken to confirm that the straight runs through this plotted points. If only one extra offset where taken and the straight did not plot on all three, there would be no indication of which offset was in error.