CONTENTS

1. GENERAL BACKGROUND

1.0 What is topography?
1.1 Purpose of this manual
1.2 Why do you need to know about topography?

Choosing a site
Surveying a site
Making a construction survey
Studying your water supply
Studying your soils

1.3 There are two kinds of lines in topography
1.4 How to plot lines in the field
1.5 How to make and use markers to plot your line
1.6 How to set out a straight line between two points

Setting out a straight line between two points visible from each other
Setting out a straight line between two points when you cannot see one from the other

1.7 How to prolong a line you have marked in the field

How to prolong a line where there is no obstacle
Prolonging a line behind an obstacle

2. MEASURING HORIZONTAL DISTANCES

2.0 Introduction

Measuring distances along straight lines
Expressing distances as horizontal measurements
Measuring distances along lines that run through obstacles
Choosing the most suitable method
Calculating perimeter lengths

2.1 How to measure distances with a ruler

Making your own ruler
Measuring short distances with your ruler

2.2 How to measure distances by pacing

Finding your own pace factor
Measuring horizontal distances by pacing
Pacing with a passometer or a pedometer

2.3 How to chain with a rope

Making your own measuring rope
Measuring horizontal distances with a rope

2.4 How to chain with bands or tapes

Measuring horizontal distances with a steel band or a tape

2.5 How to chain with a surveyor's chain

Measuring horizontal distances with a chain

2.6 How to measure distances by chaining

Chaining over horizontal ground
Chaining over sloping ground
Chaining over irregular ground
Improving the accuracy of your chaining

2.7 How to measure distances with a clisimeter

Making your own stadia staff
Measuring distances with a stadia staff
Measuring distances on sloping ground

2.8 How to measure distances by the stadia method
2.9 How to measure distances that run through obstacles

Measuring a distance across a lake or an agricultural field
Measuring a distance across a river

3. MEASURING HORIZONTAL ANGLES

3.0 Introduction

What is a horizontal angle?
Expressing horizontal angles
Some general rules about angles
Choosing the most suitable method

3.1 How to use the graphometer

Building your own graphometer
Using the home-made graphometer to measure horizontal angles
Measuring an angle with an inaccessible summit.
Measuring consecutive angles

3.2 How to use a magnetic compass

What is a magnetic compass?
Using the compass to measure horizontal angles
Measuring the azimuth of a line
Measuring a measure horizontal angle
Surveying a polygonal site
Checking when using a compass

3.3 Graphic methods for measuring horizontal angles

Using a simple compass and a protractor in the field
Using a plane-table and a protractor.
What is a protractor
Making your own protractor
Using the protractor to measure an angle you have drawn

3.4 How to measure horizontal angles by the right-angle method
3.5 How to measure horizontal angles with a theodolite
3.6 How to set out right angles or perpendiculars

What are right angles and perpendiculars
What are the main problems you will face
Dropping a perpendicular by the full-circle method
Dropping a perpendicular by the half-circle method
Setting out a perpendicular by the mid-point method
Setting out a perpendicular by the intersection method
Using the short-line intersection method
Using the long-line intersection method
Setting out a perpendicular by the 3:4:5 rule method
Making your own 3:4:5 measuring line
Using the short 3:4:5 line to set out a right angle
Using the medium 3:4:5 line to set out a right angle
Using the long 3:4:5 line to set out a right angle
Using a measuring tape to set out a right angle
Setting out a perpendicular with a cross-staff
Making your own cross-staff
Adjusting the home-made cross-staff
Using the cross-staff to set out a right angle

3.7 How set out parallel lines

What are parallel lines
Setting out parallels by the 3:4:5 rule method
Setting out parallels with the crossing-lines method
Setting out a series of rectangular areas

4. MEASURING VERTICAL ANGLES AND SLOPES

4.0 Introduction

How to express the slope of a line
Converting percentage of a slope into degrees, or degrees into percentage
Measuring and calculating slopes
Using slope to calculate horizontal distances
Choosing a method to use for measuring slopes

4.1 How to measure with the home-made clinometer, model 1
4.2 How to measure with the home-made clinometer, model 2
4.3 How to measure with the home-made clinometer, model 3
4.4 How to measure with the home-made clinometer, model 4
4.5 How to use the clisimeter

Using the clisimeter to measure a slope
Using the clisimeter to lay out a slope

4.6 How to use the optical clinometer
4.7 How to use miscellaneous levelling devices
4.8 How to set out and check verticals

Setting out and checking verticals with a plumb-line
Making your own plumb-line
Using a plumb-line to set out a vertical
Checking small verticals with a mason's level

5. MEASURING HEIGHT DIFFERENCES - PART 1

5.0 Introduction

Height differences in fish culture
Types of problems you will be facing
Measuring the height of ground points
Making your own levelling staff
Choosing the best method for measuring height differences
Calculating height differences from slopes
Calculating height differences from vertical angles
Using height differences to calculate horizontal distances

5.1 How to use the straight-edge level
5.2 How to use the line level
5.3 How to use the flexible-tube water level
5.4 How to use the T-bone level
5.5 How to use the improved T-bone level
5.6 How to use the bamboo sighting level
5.7 How to use the hand level
5.8 How to use the the surveyor's level and theodolite

6. MEASURING HEIGHT DIFFERENCES - PART 2

6.0 Introduction: contour levelling methods
6.1 How to use the mason's level

What is a mason's level?
Using a mason's level to check horizontality

6.2 How to use the A-frame level

Making your own A-frame level
Adjusting the A-frame level
Using the A-frame for contouring

6.3 How to use the A-frame and plumb-line level

Making your A-frame and plumb-line level
Adjusting your A-frame and plumb-line level

6.4 How to use the H-frame water level

Making your H-frame water level
Adjusting your H-frame water level
Using your H-frame water level for contouring

6.5 How to use the semi-circular water level

Making your own semi-circular water level
Uing your semi-circular water level for contouring

6.6 How to contour with non-sighting levels

Using the straight-edge level for contouring
Using the line level for contouring
Using the flexible-tube water level for contouring

6.7 How to contour with sighting levels

Using the bamboo sighting level for contouring
Using the hand level for contouring
Using the surveyor's level or the theodolite for contouring

6.8 How to contour with slope-measuring devices
6.9 How to set graded lines of slope

Using slope-measuring devices for setting lines of slope
Using sighting levels for setting lines of slope
Using non-sighting levels for setting lines of slope

7. TOPOGRAPHICAL SURVEYS - PLAN SURVEYING

7.0 Introduction

What is a topographical survey?
What do topographical surveys involve?
Planning your topographical surveys
What are the main methods used in plan surveying?

7.1 How to survey by traversing

What is a traverse?
Which method should be used for traversing?
Choosing the route of a traverse
Surveying an open traverse with a magnetic compass
Adjusting an open traverse
Surveying a closed traverse with a magnetic compass
Adjusting a closed traverse

7.2 How to survey by radiating

What is a radiating survey?
Choosing the observation station
Choosing a method for radiating surveys
Caraying out a radiating plan survey with a magnetic compass

7.3 How to survey by offset

What is an offset?
Surveying by offset

7.4 How to survey by triangulation

What is triangulation?
Using the triangulation method

7.5 How to use the plane-table

What is a plane-table?
Making a very simple plane-table
Making an improved plane-table
Making your own alidade
Using the plane-table
What are the advantages of plane-tabling?
What are the disadvantages of plane-tabling?
Covering the board with drawing paper
Setting up the plane-table
Orienting the plane-table
Plane-tabling methods for reconnaissance surveys
Plane-tabling for plotting details
Measuring horizontal angles by plane-tabling

8. TOPOGRAPHICAL SURVEYS - DIRECT LEVELLING

8.0 Introduction

What are elevation and altitude?
What are the main levelling methods?
What are the kinds of direct levelling?

8.1 How to level by differential

What is differential levelling?
What are backsights and foresights?
Surveying two points with one turning point
Surveying two points using several turning points
Making topographical surveys by straight open traverses
Making topographical surveys by broken open traverses
Checking on levelling errors
Making topographical surveys by closed traverses
Making topographical surveys by the square grid
Making topographical radiating surveys
Combining traversing and composite radiating
Making topographical surveys with non-sighting levels
Making bench-marks for topographical surveys

8.2 How to level by profile

What is the purpose of profile levelling?
What does profile levelling consists of?
Longitudinal profile levelling by radiating
Longitudinal profile levelling by traversing
Cross-section profile levelling

8.3 How to contour

What is a contour?
What is contouring?
What are the main methods for contouring?
Selecting the contouring method
Laying out contours on the ground with a sighting level
Laying out contours with a non-sighting level
Contouring by the indirect method

9. TOPOGRAPHICAL PLANS AND MAPS

9.0 Introduction

What are topographical plans and maps?
Starting topographical plans and maps

9.1 How to make scales for plans and maps

What is the scale of a plan or map?
Expressing a scale
Choosing a scale

9.2. How to make a map by plane-tabling

Mapping an open traverse with a plane-table
Mapping an closed traverse with a plane-table
Mapping with a plane-table by radiating
Mapping with a plane-table by triangulation
Mapping with a plane-table by combined methods

9.3 How to map by protractor and scale
9.4 How to map contours

What is a contour line?
What are the characteristics of contour lines?
Choosing the contour interval of contour lines
Making a contour map

9.5 How to plot longitudinal profiles

Why are longitudinal profiles plotted?
Information from which longitudinal profiles can be plotted
Scales to be used for longitudinal profiles
Plotting profiles from contour maps
Plotting profiles from your own field survey

9.6 How to plot cross-section profiles

Plotting cross-section profiles from contour maps
Plotting cross-section profiles for earth-work estimates

10. MEASUREMENT OF AREAS

10.1 Introduction
10.2 How to use the strips method for measuring areas
10.3 How to use the square-grid method for measuring areas
10.4 How to subdivide the area into regular geometrical figures

Measuring areas by triangles
Using a base line to subdivide land areas
Subdividing land areas without base lines

10.5 How to measure areas bounded by a curve

11. TOPOGRAPHY AND FRESHWATER FISH CULTURE

11.0 What you have learned
11.1 How to make preliminary studies from topographical maps

Finding the size of the drainage area and the availability of water for fish culture
Finding the size of the area to be flooded
Obtaining ground profiles from topographical maps
Finding differences in elevation along a stream
Determining the shape of stream valleys
Making a slope map from a topographical map

11.2 How to make a reconnaissance survey of a possible site

Studying the longitudinal profile of the stream valley
Making cross-section profiles of the potential site
Contour-mapping of the potential site
Finding the maximum area of a reservoir

11.3 How to make a feasibility study of a potential site

Estimating the area of the future reservoir
Estimating the volume of the future reservoir
Estimating the volume of an earth dam
Using what you know about topography to install a pumping station

11.4 How to make levelling surveys for fish-farm construction

Staking out a water supply canal for construction
Staking out a pond bottom before construction

ANNEX I - Some useful mathematical formulae for regular geometrical figures

ANNEX II - Tangents and values of angles

ANNEX III - Cosine values of angles