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CSE 344: ENGINEERING SURVEYING IV
COURSE OUTLINE
Introduction to Underground Surveying: Mapping of open and underground mines
...
Shaft
plumbing and other special procedures in underground mining
...

Aerial Photography: Introduction, aerial cameras, scale of photography, stereoscopy, parallax,
heights from parallax measurements, flight planning, applications
...
Photointerpretation: Principles, procedures, equipment, factors
affecting interpretation
...

Introduction to Geographic Information Systems: Definition, fundamental principles,
hardware, peripherals, software and data
...
Geomatics By Barry F
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2
...
Price
3
...
Surveying By Bannister
5
...
A
6
...
Plane Surveying

Lecture Notes

CSE 344: Engineering Surveying 1V

By Dr
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A

1
...
1 Definition and Role
This is surveying conducted to facilitate the locations, construction, deformation monitoring and
mapping performed beneath the surface of the earth in connection with tunneling, exploration of
caves and construction in subterranean passageways
...

Underground surveys are essentially similar to three dimensional surveys on the surface in that the
purpose of all angle and distance measurements is to obtain the horizontal and vertical coordinates
of a point, the position of which is unknown with respect to a point of established location
...
The underground surveying techniques employed
for the purpose do not differ characteristically from the land surveying methods
...


The following peculiarities of underground surveys indicate how they differ from surface surveys:
1
...

2
...
Instrument stations and benchmarks for leveling must often be set into the roof of a
passageway to minimize disturbance from the operations being carried on in the workings
...
Lines of sight are frequently very short either because of crooked passageways or because
alignment must often be brought down from the surface through small shafts
...
The sights taken in shafts and sloping passageways are often sharply inclined and it is
frequently necessary to observe both horizontal and vertical angles through a prismatic
telescope or eyepiece or through an auxiliary telescope mounted either above the main
telescope or to one side of the instrument standards
...
Plumbing down the shaft constitutes a special problem which is peculiar to underground
surveying
...
Khaemba W
...
2 Applications of Underground Surveys
The major application of underground surveys is in the construction of tunnel and other
underground utilities
...
It;
1
...
Shortens the distance between given points separated by a dividing mountain or ridge
3
...

The survey work in connection with tunneling can be divided into:
(a) Surface survey
(b) Transferring the alignment underground
(c) Levels in tunnels
(d) Underground setting out
...
3 Methods of Orientation
The essential problem in underground surveying is that of orienting the underground surveys to
the surface surveys
...


If entry into the underground tunnel system is via an inclined shaft, then the surface may be
extended and continued down that shaft and into the tunnel by the method of traversing
...


3

Lecture Notes

CSE 344: Engineering Surveying 1V

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A

1) Optical Methods
Where the shaft is shallow and of relatively large diameter, the bearing of a surface line may be
transferred to the shaft bottom by theodolite as follows:
B

Theodolite

Theodolite

A

c

d
Shaft

Tunnel
B’

A’

If a tunnel is to be dug in a particular direction represented by the surface control points A and B;
then:
•

Auxilliary stations c and d are very carefully aligned with A and B using the theodolite on both
faces
...


If the coordinates of d are known then the coordinates of B’ could be fixed by measuring the
vertical angle and distance (EDM) to a reflector at B’
...


2) Gyroscopic Methods
A north-seeking gyroscope integrated with a theodolite can be used to orient underground base
lines relative to the True North
...
When the earth’s rotation acts on a gyro, it responds in such a way that it can be
employed as a north-seeking instrument
...
They give better accuracy than
wire methods described below
...
Khaemba W
...
The plumb wires produce a
vertical reference plane and on the surface the plane can be in the line of sight of a correctly
oriented theodolite
...
The line of
sight when established can be used to set up floor or roof stations within the tunnel
...

The basic concept is that wires hanging freely in a shaft will occupy the same position
underground that they do on the surface, and hence the bearing of the wire plane will remain
constant throughout the shaft
...
The principle
is to obtain the bearing and coordinates of the wire base relative to the surface base
...
In the figure, A and B are two points through
which wires are suspended through the vertical shaft for the transfer of the surface-line through A
and B, into the underground working
...


5

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CSE 344: Engineering Surveying 1V

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A

C and D, the corresponding points of A and B, are shown in plan
...
The theodolite is set upon a point conveniently offset from the
line CD
...
With the theodolite leveled and
centred on O, the angle COD is measured very accurately
...


P
Y

Q

b

A

X
Tunnel
Underground
base

Wu

a
ws

B

Ws

Shaft

b) Co-planing
In this method the triangle of the previous method is eliminated by aligning the theodolite at Ws
exactly with the wires W1 and W2 by trial and error; focussing first on the front wire then on the
back
...

6

Lecture Notes

CSE 344: Engineering Surveying 1V

A

By Dr
...
A

B
Surface base

W2

W1

Ws
Co-planed station

The instrument should be set up within 3 to 4 m of the nearer wire and special care taken to ensure
that the tripod head is level
...

c) Single Wire in Two Shafts
Where two shafts are available, orientation can be achieved via a single wire in each shaft
...


A

B

Shaft

Shaft

Z

X

Underground
Tunnel
Y

Wires A and B are coordinated into the surface control network by multiple intersection from as
many surface stations as possible
...

A “ray trace” traverse is then carried out from A to B via an underground connecting tunnel i
...

using an assumed bearing AX as the angles at A and B cannot be measured
...
Khaemba W
...

The resulting linear error is corrected by multiplying each length by a scale factor equal to length
AB/ length AB’
...


This is the most accurate and reliable method of surface-to-underground orientation
...
4 Levels in Tunnels
In transferring levels underground, little difficulty is encountered at the ends of the tunnel but at
the shaft use is made of (i) steel tape, (ii) chain, (iii) specially constructed rods, (iv) steel wires
...
In modern days EDM is also used
...
Khaemba W
...
5 Introduction to Hydrographic Surveying
1
...
1 Definition
Hydrographic Surveying: The term hydrographic surveying is used in the broad sense of the
meaning of two words, namely to describe that part of the surveying discipline concerned with the
measurement analysis and description of the physical features natural and man made of that part of
the earth included in the marine environment
...
The concept and the principle of measurement, processing and analysis of
hydrographic surveying information
...
Although the oldest existing charts were drawn in Italy in the 14th Century evidence
exists that mariners had some sort of description information much earlier
...
Since the end of World War II, during and since which technology has
advanced at a faster pace than never before, increased offshore activity has been taking place
occasioned by our needs for food mineral and energy resources, with the increased activity the
scope of challenges and resulting activities of the hydrographic surveyor have broadened
...
Khaemba W
...
5
...
The primary tasks are:
The determination of a vessels position in a specified coordinate system
The determination of the position on the sea floor in a specified coordinate system
The establishment of some reference position ashore to facilitate the offshore survey
...

1
...
3 Surveying Tasks for Hydrography
The following are some of the surveying tasks for hydrography
...

(1) The delineation of the sea floor topography including all natural and man-made features for the
production of the charts to afford safe navigation to marines
(2) The mapping of geological and geophysical information used in the exploration of natural
resources
...

(5) Environmental projects designed to prevent environmentally damaging action or the clean-up
required after a mishap (catastrophe)
(6) The determination of legal boundaries at sea
...


10

Lecture Notes

CSE 344: Engineering Surveying 1V

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A

1
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4 Hydrographic Surveying Techniques
Hydrographic surveying measurements basically involve:
(a) determination of the position of a point on the water surface in a specified coordinate system
(b) determination of the depth of the sea bed below this point
...


There are four major differences between determining position on land and at sea
...
Direct measurements to
monumented shore controls involves distances in the range of 50-500km whereas on land one
talk of 5-20 km distances
...


(ii) Observation station at sea in not stationery as on land but is constantly moving to some extent
from oscillation of a few metres on an off shore drilling platform to translations of several
metres per second on a ship
...
This is unnecessary on land and the accuracies obtained under
these conditions at sea are lower than on land
...
Electromagnetic distance measuring
instruments used in continental geodetic positioning must have a straight line of sight for
measured electromagnetic signals
...
At lower frequency electromagnetic signals are used
...
Also an extremely new
propagation mode is used at sea i
...
acoustic wave through water
...


(iv) Heights and depth
...
At sea we are on something close to the geoid and we measure how far below us the
terrain is
...
Khaemba W
...
5
...

Theodolite, level, tacheometer, subtense bar: – exclusively on land special cases – stationary
platform, topo survey of marine environment
...


Electronic Distance Measurements
Many types of instrument
- for positioning
- for sounding
The observables are also different

Satellite navigation and positioning
...
g
...

Navigation - positioning in real time and the parameters of motion (moving platform and keeping
track of motion parameters)
...

Receiving systems at sea give position from satellite signals
...

Sounding system
...

Acoustic waves are very good in long distances at acceptable accuracies
...

Systems that are in-built to give positions in real time (does not use signals or measurements)
...
e
...
Inertial survey System (ISS), in-built gyro
system
...
Has no
land use due to accuracy requirements
...
5
...
There are three types of sextants in use classified by their design
...
Khaemba W
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1 of a minute of arc
...
e
...

O

i
i

H

M

e
e

a
E

I

D
C

α
A

Figure 1
The basic physical construction of a sextant is shown in figure 1
...
I is the horizon glass mirror attached to the frame of the instrument
...
The second reference object
13

Lecture Notes

CSE 344: Engineering Surveying 1V

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A

O is also observed at E from the mirror at I with the help of the index mirror M
...
The angle
indicated on the graduated arc CD when coincidence is observed from E is the actual angle a
subtended by the two reference objects O and H at the observer’s position
...
5
...

(ii) Photogrammetry can be used for surface and sub surface current direction and rates
determination
...

(iv) Location of channels and estimates of depth
...


QUESTIONS
Q1
...
1)
...
The distances AC and BC were 6
...
2998 m respectively
...

A

B

D

3
...
4782 m

C

Fig
...


P

The centre line of a tunnel is represented by two plumb bobs at A and B, 400 m apart,
hanging vertically in a shaft (Figure 2)
...
A theodolite
is set up at C in the tunnel, roughly east of the near plumbline at B and at a distance of
4
...
The observed value of angle ACB is 16’ 30”
...
Khaemba W
...
2
Calculate the bearing of line AC and the perpendicular distance of C from the centre line of
the tunnel
...


A, B and C in Figure 3 are three ground control points on a coastline and P is a sounding
station at sea whose position is to be determined
...
AB = 482 m, BC =
344 m and θ =143° 30’
...
3

β
P

15

Lecture Notes

CSE 344: Engineering Surveying 1V

By Dr
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A

2
...
1 Introduction
Photogrammetry is the art, science and technology of obtaining reliable information about
physical objects and the environment through processes of recording, measuring and interpreting
photographic images and patterns of recorded radiant electromagnetic energy and other
phenomena
...


2
...
Terrestrial photogrammety – Uses terrestrial photographs i
...
Aerial photogrammetry – Uses aerial photographs i
...
Close range photogrammetry – Uses photographs taken with a camera close to the object i
...
Normally used for mapping small engineering projects and architectural monuments
4
...
2
...


Terrestrial photographs are taken with ground –based cameras, the position and orientation of
which are often measured directly at the time of exposure
...
These special
cameras are called phototheodolites
...

Depending on the size of the inclination of the optical axis away from the vertical at the instance
of exposure, the photograph can fall under vertical, tilted or oblique photographs
...
Khaemba W
...
When
the camera axis is unintentionally tilted slightly from the vertical, the resulting photograph is
called a tilted photograph
...

(iii) Oblique photograph
Are those taken with the optical axis of the lens intentionally deviated or tilted from the vertical
axis and the degree of tilt depends on the use
...


•

A high oblique has a relatively large or high angle of deviation from the vertical and
includes the apparent horizon

Vertical

High oblique

Low oblique

2
...
They expose a square shaped area of the ground all at one instance of time
...

17

Lecture Notes

CSE 344: Engineering Surveying 1V

By Dr
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A

b) Multi-lens frame camera
These have the basic characteristics of single-lens frame cameras except that they have two or
more lenses and expose two or more pictures simultaneously
...

The different cameras contain films with emulsions that are sensitive to different regions of the
electromagnetic energy spectrum, hence are sometimes referred to as multispectral cameras

c) Strip camera
Strip cameras expose a continuous photograph of a strip of terrain beneath the path of the aircraft
...

The speed of the film across the slit is a function of the height of the camera above ground, focal
length of the lens and the ground velocity of the aircraft
...
The camera takes sweeping pictures
of the ground from right to left
...
Khaemba W
...
Contained within this
assembly are the lens, filter, Shutter and diaphragm
...

Lenses are classified into narrow angle, normal angle, wide angle and super wide angle
...
The shutter controls the length of time that
light is permitted to pass through the lens while the diaphragm controls the amount of light
passing through the lens by varying the size of the aperture opening
...


19

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CSE 344: Engineering Surveying 1V

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A

The inner cone
This holds the lens assembly fixed w
...
t the upper surface called the focal plane
...


The focal plane
The focal plane is located at such a distance from the rear nodal point of the lens system so as to
give the best focus of the overall image
...


Outer cone and camera body
The function of the outer cone and body of camera is to support the iner cone and hold the drive
mechanism and support the magazine
...
It also holds the film advancing
and film flattening mechanisms
...


Camera Accessories
These are for the proper functioning of an aerial camera
...
Khaemba W
...
4 Scale of photography
Map scale is ordinarily interpreted as the ratio of a map distance to the corresponding distance on
the ground
...
On a map scale is everywhere uniform because a map is an
orthographic projection
...
Scales may be expresses as unit equivalents,
dimensionless representative fractions, or dimensionless ratios i
...
4
...
Since measurements
are normally taken from photo positives rather than negatives, the negative has been excluded
from this
...
That scale may be expressed in terms of
camera focal length f and flying height above ground H’ by equating similar triangles Lab and
LAB as follows
S=

ab
AB

=

f
H’

The scale of a vertical photo is therefore directly proportional to camera focal length (image
distance) and inversely proportional to flying height above ground (Object distance)
...
4mm) focal –
length camera from an altitude of 6000ft above ground
...

21

Lecture Notes

CSE 344: Engineering Surveying 1V

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A

2
...
2 Scale of a vertical photograph over variable terrain
If the photographed terrain varies in elevation, object distance will also be variable and photo scale
will likewise vary
...
Suppose a vertical photograph is taken over variable terrain from
exposure station L in figure below
...
Photographic scale at h, the elevation of points A and B, is equal to the ratio of photo
distance ab to ground distance AB
...
In general, by dropping subscripts, the scale at any point whose elevation above datum is h
may be expressed as
S

=

f
H–h

In this equation, scale of a vertical photograph is seen to be simply the ratio of image distance to
object distance
...
For vertical photographs taken over variable terrain, there is infinite
number of different scales
...
Khaemba W
...
4
...
Average scale is the scale at the average elevation
of the terrain covered by a particular photograph and is expressed as
Savg

=

f
H - havg

2
...
5
...

Relative distances of objects can be judged on the following basis
...

These allow only rough judgement or appreciation of depth
...
Khaemba W
...


Eye base

dA
dB

f

ФA

ФB

dB - dA

Rays of light emanate from the object to the observer’s eye
...
These angles are known as parallactic angles and depth is appreciated on the
basis of variation of these angles
...
This method of vision has a higher accuracy than the
monoscopic method
...
The thickness of the human eye lens is
changed by the eye muscles thus accommodating the required value
...
Khaemba W
...
5
...
There are
two basic types of stereoscopes:
a)
...
mirror stereoscope

a) The Lens Stereoscope
The lens stereoscope consist of 2 simple convex lenses mounted on a frame supported at
fixed distance above the table top this is originally less than the focal length to the lenses
so that rays entering the lens from the table top

appear to come from some finite

distance
...

Overlap area

f
a1

Obscured area

a2

Table
top

A

Lens stereoscopes magnify images by about twice
...
If the separation btw
conjugate points for viewing with a lens stereoscope is about 50mm or so, 90mm area will
have to be obscured by one photograph lying on another thereby preventing stereo-viewing
...
Khaemba W
...

The mirror stereoscope eliminate the problem by permitting the two photographs to be
completely separated when viewing stereoscopically
...

The light rays are reflected

as shown above thereby creating stereovision
...
The focal length of the eyepiece
lenses is slightly greater than the total path of the reflected ray thus achieving the same
purpose as the lens stereoscope
...

2
...
3 Other Methods of Image Separation for Stereoscopic Viewing
(i) Anaglyphic Viewing
This is a system where two images of the same object printed in two complimentary
colours are viewed simultaneously
...
Most often the complimentary colours used are red and
blue - green
...


For Digital Photogrammetric Workstations the most popular methods are the LCS Principle and
polarising filters:

26

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A

(ii) Liquid Crystal Shutter (LCS) Principle (active glasses)

LCD Principle
Stereoscopic view on the monitor is obtained by using active glasses that alternately display the
two images
...
The
display and the glasses are synchronized by an infrared emitter which is located on the monitor so
that several people can watch the stereo model
...
Glasses cost about 1500 $
...
Several observers possible
...
Khaemba W
...
Glasses don’t require batteries
...
Glasses are
smaller than active glasses
...


2
...
If the photographs are
interchanged, i
...
the right with the left and vice versa, then pseudoscopic view results, i
...

depressions become crests and crests become depressions
...

This condition is fulfilled by adopting the following procedure:

1
...
Determine the conjugate principal points of overlapping photographs i
...
locations of principal
points of adjacent photographs
...
Khaemba W
...

3
...

L

R

O1’
O2

O2’

o1

Where o1 and o2 are the principal points of the left and right photographs and o1’ and o2’ are the
corresponding conjugate points respectively
...
Orient the photographs so that o1, o2’, o1’ and o2 all lie on a straight line
...


...


R
o1

O2’

O1’

O2

flight line


...
Depending on the stereoscope, separate the photographs apart so that the separation between
conjugate points e
...
o1’ and o1 is the same as the eye base
...
Place the stereoscope over the pair of photographs so that the line joining the eyepiece centres
is parallel to the flight line
...


2
...
1 Y – Parallax
For comfortable stereo vision, the line joining conjugate principal points of corresponding points
should be parallel to the flight line
...
Any slight amount of Y parallax causes eyestrain
and excessive amounts prevent stereoscopic viewing altogether
...
Factors causing Y parallax include:
•

Variations in flying height
29

Lecture Notes

CSE 344: Engineering Surveying 1V

•

Variations in verticality (presence of tilt)

•

Misalignment of the stereoscope

•

By Dr
...
A

Improper orientation of the photos

2
...
2 Vertical exaggeration
Normally the vertical scale of a stereomodel will appear to be greater than the horizontal scale i
...
This apparent scale disparity is called vertical exaggeration
...
the vertical exaggeration can be
approximated by the formula:
V

= B
H

x

h
b

The photographic base-height ratio B/H = (1 – ov) x d/f
Where ov = overlap in %
d = format dimension
f = focal length
The stereoviewing base-height ratio is a somewhat difficult variable to measure and it differs
slightly among individuals
...
15
...
6
...
Khaemba W
...
Khaemba W
...
The photo bases were measured as 90
...
90mm respectively
...
55mm and 18
...
Given that elevation of Q was 221m above datum, compute
elevation of R assuming that points imaged at principal point were at havg = 221m
...
Khaemba W
...
7 Flight planning
Planning for a photogrammetric project using aerial photos consists of 3 basic interrelated phases
namely:
(i) Development of a flight plan which must be followed when taking the aerial photographs to be
used in the project
...

(iii) Estimating the costs involved in the project

If the photography is to satisfactorily serve its intended purposes, the photographic mission must
be carefully planned and faithfully executed according to the flight plan
...


The basic elements in flight planning therefore are the flying height above datum (msl), the ground
distances between successive exposures and between flight lines
...
This resulting flight line
map is the so called flight map
...
Purpose of photography
The majority of the photogrammetric activities involve the compilation of the topographic map in
a stereoplotter
...
Large B/H ratios denote low
33

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A

flying heights and large x parallaxes, conditions favorable for higher accuracy
...


Photography flown for aerial mosaic should ideally be flown from as high an altitude as is feasible
and should contain overlap commensurate with the topography
...


Photography taken for the production of orthophotos is usually used also for map compilation
...


2
...
Flying heights used in photographying for
topographic mapping normally vary from b/n 500m to 10000m
...

At high flying heights we encounter problems of decreasing oxygen, decreasing pressure, extreme
cold etc
...
4mm focal length camera over a terrain whose average elevation is 426
...
What is the required flying height above mean sea level
...
Crab and drift
Crab is a disparity in the orientation of the camera in the aircraft with respect to the aircraft’s
actual travel direction
...
It is caused by not having the focal plane of the
camera squared with the direction of flight at the instant of exposure
...
Khaemba W
...

Rotating the viewfinder so as to cause the images of the ground underneath to travel parallel with
the edges of the viewfinder frame eliminates the effect of crab
...
It is often
caused by strong winds
...
Excessive drifts are most common
cause for gaps in photo coverage
...


4
...


B

B

Overlap
G

In the figure, G represents the dimension of the square of ground covered by a single photograph
and B is the airbase or distance between exposure stations of a stereopair
...
It is expressed as

Overlap = (G – B) x 100
G
If a stereoscopic coverage of an area is required, the absolute minimum endlap is 50%
...
Also if the photos are to be used for
photogrammetric control or extension, images of some points must appear on 3 successive photos
a condition requiring greater than 50%
...


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A

Sidelap is the overlapping of successive strips
...


W

W

Sidelap

G

From the figure, G again represents the dimension of the square of the ground coverage of a single
photograph and W is the spacing between adjacent flight lines
...
An advantage realized from
using this large percent is elimination of the need to use the extreme edges of the photo where the
imagery is of poor quality
...

The camera has 152
...
What is the overlap? Assuming the
spacing between adjacent flight strips is 2500m
...
Ground coverage
Once average photographic scale and camera format dimensions have been selected, the ground
area covered by the stereoscopic neat model can be determined
...

36

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CSE 344: Engineering Surveying 1V

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...
A

Consider a stereomodel

pp

PP is at middle i
...
e
20/2 = 10%

The neatmodel is basically 80% x 40% of the photo format with a standard overlap of 60% and
sidelap of 20%
...
4mm focal length and 23cm format
...
What is the round area covered by a single photo and by the stereoscopic neat model?
2
...
1 Computation of flight plan
Data required to compute the quantities for delineating the flight map lines, determine the time
interval between exposures and determine the amount of film needed to complete the photography
are:
•

Focal length

•

Flying height above m
...
l

•

Size of photograph

•

Size of area to be photographed

•

Position of outer flight lines w
...
t the boundary of area

•

Overlap

•

Sidelap

•

Scale of flight map

•

Ground speed of aircraft

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CSE 344: Engineering Surveying 1V

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A

Example 1
An area that is 24km long in the N-S direction and 14km wide in the E-W direction is to be
photographed with a lens having 302mm focal length for the purpose of constructing a mosaic
...
The average scale is to be 1:12000 effective at an average
elevation of 220m above m
...
l
...
An
intervalometer will be used to control the interval of exposures
...
The flight lines are to be laid out in a N-S direction on an existing
map having a scale of 1:62,500
...
Determine the data for the flight plan
...
6km long with very little relief is to be photographed in 1
strip for compiling a topo map
...
The focal length is 147
...
The viewfinder will be used to
obtain the proper overlap of 65%, 2 exposures are to be provided at each end of the flight line
...
compute
the data for the flight plan
...
Khaemba W
...
8 Applications of Aerial Photography in Civil and Structural Engineering
...
Many maps are
prepared which vary in scale from large to small and are used in planning and designing highways,
railroads, rapid transit systems, bridges, pipelines, aqueducts, transmission lines, hydroelectric
dams, flood-control structures, river and harbour improvements, urban renewal systems etc

Highway Engineering
In the field of highway planning and design, aerial mosaics are prepared for use in area and
corridor studies and to select the best route
...
Small-scale topographic maps are prepared for
use in preliminary planning; large-scale topographic maps are compiled for use in final design;
earthwork cross-sections are taken to obtain contract quantities
...
This has reduced costs and enabled better overall highway
designs to be achieved
...

Photographs may be used in land use studies to enable travel patterns to be estimated and
predicted
...
The use of electronic scanners capable of sensing
vehicles on infra-red photography eliminates the need for actual counting of the cars
...

The photos provide a visual inspection of a large area at a glance and can be taken to show on- and
off-peak flows, normal and congested routes, non-utilisation of streets, parking characteristics,
junction studies, effect of public transport on traffic flows, etc
...

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A

Time lapse photography may also be used to re-construct an accident scene with the advantage of
not leaving out any details as photography records the entire scene
...


Mining Engineering
Aerial and close range photography techniques can also be applied to mining engineering in
determining the stability of, and volume of material removed from, open-cast mines and quarries
and measuring tunnel profiles
...

Photography records the entire structure, and so many more points on the object can be measured
efficiently
...
Khaemba W
...
INTRODUCTION TO REMOTE SENSING
3
...
M Lillessand and R
...


Remote sensing is the science and art of acquiring information about the Earth's surface without
actually being in contact with it
...
Energy Source or Illumination (A) - the first requirement for remote sensing is to have
an energy source which illuminates or provides electromagnetic energy to the target of
interest
...
Radiation and the Atmosphere (B) - as the energy travels from its source to the target, it
will come in contact with and interact with the atmosphere it passes through
...


3
...

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A

4
...

5
...

6
...

7
...

These seven elements comprise the remote sensing process from beginning to end
...
2 Electromagnetic radiation
Electromagnetic energy/radiation is the means by which information is transmitted from an object
(target) to a sensor
...
This energy is in the form of electromagnetic radiation
...
Electromagnetic radiation consists of an electrical field (E)
which varies in magnitude in a direction perpendicular to the direction in which the radiation is
traveling, and a magnetic field (M) oriented at right angles to the electrical field
...


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A

Two characteristics of electromagnetic radiation are particularly important for understanding
remote sensing
...


The wavelength is the length of one wave cycle, which can be measured as the distance between
successive wave crests
...

Wavelength is measured in metres (m) or some factor of metres such as nanometres (nm, 10-9
metres), micrometres (mm, 10-6 metres) (mm, 10-6 metres) or centimetres (cm, 10-2 metres)
...

Frequency is normally measured in hertz (Hz), equivalent to one cycle per second, and various
multiples of hertz
...
Khaemba W
...
Therefore, the two are inversely related to
each other
...
The longer the wavelength, the
lower the frequency
...


3
...
1 Nature of Electromagnetic radiation (view of Quantum Mechanics)

Controversy in physics over the last 250 years
...

(Wave-like form of energy)

Corpuscular theory

Considers radiation as a stream of particles
so called photons

Importance to remote sensing
The wave-like characteristics of EMR
allows the distinction with regard to
wavelength e
...


Particle nature considered in order to
understand the interactions between the
Earth’s atmosphere and the surface

Today’s view of quantum mechanics : EMR is both a wave and a stream of particles
...
2
...
There are several
regions of the electromagnetic spectrum which are useful for remote sensing
...
Khaemba W
...
This radiation is just beyond the violet portion of the
visible wavelengths, hence its name
...


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The light which our eyes - our "remote sensors" - can detect is part of the visible spectrum
...
There is
a lot of radiation around us which is "invisible" to our eyes, but can be detected by other remote
sensing instruments and used to our advantage
...
4 to 0
...
The longest visible wavelength is red and the shortest is violet
...
4 - 0
...
45 - 0
...
50 - 0
...
58 - 0
...
6 - 0
...
62 - 0
...
They are
defined as such because no single primary colour can be created from the other two, but all other
colours can be formed by combining blue, green, and red
...
Khaemba W
...
7 mm to 100 mm - more than 100 times as wide as the
visible portion! The infrared region can be divided into two categories based on their radiation
properties - the reflected IR, and the emitted or thermal IR
...
The
reflected IR covers wavelengths from approximately 0
...
0 mm
...
The thermal IR covers wavelengths
from approximately 3
...


The portion of the spectrum of more recent interest to remote sensing is the microwave region
from about 1 mm to 1 m
...
The
shorter wavelengths have properties similar to the thermal infrared region while the longer
wavelengths approach the wavelengths used for radio broadcasts
...
3 Interaction of Electromagnetic radiation with the Atmosphere
As the energy travels from a source (the sun) to the target (the Earth’s surface) it interacts with the
Earth’s atmosphere
...
Particles and gases in the atmosphere can affect the incoming
light and radiation
...
How much
scattering takes place depends on several factors including
• the wavelength

of the radiation,
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• the abundance of particles
• the distance the radiation

By Dr
...
A

or gases, and

travels through the atmosphere
...


a) Rayleigh scattering
Rayleigh scattering occurs when particles are very small compared to the wavelength of
the radiation
...

(about 0
...
501µm)
Rayleigh scattering causes shorter wavelengths of energy to be scattered much more than
longer wavelengths
...

Remarks
The fact that the sky appears "blue" during the day is because of this phenomenon
...
e
...
At sunrise and sunset the light has to
travel farther through the atmosphere than at midday and the scattering of the shorter wavelengths
is more complete; this leaves a greater proportion of the longer wavelengths to penetrate the
atmosphere
...
Khaemba W
...
4 – 0
...

Dust, pollen, smoke and water vapour are common causes of Mie scattering
Tends to affect longer wavelengths than those affected by Rayleigh scattering
...
e scattering affects specific wavelengths of
energy
...

Particles : water droplets, large dust particles, ice fragments
All wavelengths are scattered about equally
...


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Absorption
Absorption is the other main mechanism at work when electromagnetic radiation interacts with the
atmosphere
...


The three main constituents (gases) which absorb radiation are
Ozone,
carbon dioxide,
water vapour
Ozone absorbs the harmful (to most living things) ultraviolet radiation from the sun
...

Carbon dioxide referred to as “a greenhouse gas”
...
– causing global warming
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Water vapour in the atmosphere absorbs much of the incoming long wave infrared and
shortwave microwave radiation (between 22mm and 1mm)
...
For
example, the air mass above a desert would have very little water vapour to absorb energy, while
the tropics would have high concentrations of water vapour (i
...
high humidity)
...
Those areas of the
spectrum which are not severely influenced by atmospheric absorption and thus, are useful to
remote sensors, are called atmospheric windows
...

The visible portion of the spectrum, to which our eyes are most sensitive, corresponds to
both an atmospheric window and the peak energy level of the sun
...


3
...
There are three (3) forms of interaction that can take place when energy
strikes, or is incident upon the surface
...
Khaemba W
...
The
proportions of each will depend on:
the wavelength of the energy and
the material and condition of the target
...

Reflection (R) occurs when radiation "bounces" off the target and is redirected
...
We refer to two types of
reflection, which represent the two extreme ends of the way in which energy is reflected from a
target: specular reflection and diffuse reflection
...
Khaemba W
...
Whether a particular target reflects specularly or diffusely, or somewhere in between,
depends on the surface roughness of the feature in comparison to the wavelength of the incoming
radiation
...
For example, fine-grained sand would
appear fairly smooth to long wavelength microwaves but would appear quite rough to the visible
wavelengths
...

Leaves: A chemical compound in leaves called chlorophyll strongly absorbs radiation in the red
and blue wavelengths but reflects green wavelengths
...
In autumn, there is less chlorophyll in the
leaves, so there is less absorption and proportionately more reflection of the red wavelengths,
making the leaves appear red or yellow (yellow is a combination of red and green wavelengths)
...
Thus water typically looks blue or blue-green due to stronger
reflectance at these shorter wavelengths, and darker if viewed at red or near infrared wavelengths
...


Note that rough/smooth is defined by surface variations or particle sizes that make up the surface
in comparison to the wavelength of the incoming radiation
For example: fine grained sand would appear fairly smooth to microwaves (long wavelength) but
quite rough to the visible (short wavelength)

3
...
The sun's
energy is either reflected, as it is for visible wavelengths, or absorbed and then re-emitted, as it is
for thermal infrared wavelengths
...
Khaemba W
...

Can only be used to detect energy when the naturally occurring energy is available
...

For re-emitted energy (such as thermal infrared) can be detected day or night, as long as
the amount of energy is large enough to be recorded
...
The sensor
emits radiation which is directed toward the target to be investigated
...

Advantages for active sensors include:
the ability to obtain measurements anytime, regardless of the time of day or season
...


However, active systems require the generation of a fairly large amount of energy to adequately
illuminate targets
...


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3
...
6
...
Platforms for
remote sensors may be situated on the ground, on an aircraft or balloon (or some other platform
within the Earth's atmosphere), or on a spacecraft or satellite outside of the Earth's atmosphere
(a)

Ground based
•

•

(b)

Ground-based sensors are often used to record
detailed information about the surface which is
compared with information collected from
aircraft or satellite sensors
...

Sensors may be placed on a ladder, scaffolding,
tall building, cherry-picker, crane, etc
...
Aircraft are often used to collect very
detailed images and facilitate the collection of
data over virtually any portion of the Earth's
surface at any time
...

Satellites are objects which revolve around another object - in this case, the Earth
...

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Because of their orbits, satellites permit repetitive coverage of the Earth's surface on a continuing
basis
...


Space Shuttle

satellites

3
...
It
can then be processed and delivered to the end user
...
The technologies designed to accomplish this can also be used by
an aerial platform if the data are urgently needed on the surface

There are three main options for transmitting data acquired by satellites to the surface
...


The data can be directly transmitted to Earth if a Ground Receiving Station (GRS)
is in the line of sight of the satellite (A)
...


If this is not the case, the data can be recorded on board the satellite (B) for
transmission to a GRS at a later time
...


Data can also be relayed to the GRS through the Tracking and Data Relay
Satellite System (TDRSS) (C), which consists of a series of communications satellites in
geosynchronous orbit
...


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A

The data are received at the GRS in a raw digital format
...
The data are written to some form of storage medium such as tape, disk or
CD
...


For many sensors it is possible to provide customers with quick-turnaround imagery when they
need data as quickly as possible after it is collected
...
Such imagery can then be faxed or transmitted digitally to end users
...
Real-time processing of imagery in airborne systems has been used, for example, to pass
thermal infrared imagery to forest fire fighters right at the scene
...
The
spatial and radiometric quality of these types of data products is degraded, but they are useful for
ensuring that the overall quality, coverage and cloud cover of the data is appropriate
...
Khaemba W
...
8 Analysis and Interpretation
3
...
1 Introduction
In order to take advantage of and make good use of remote sensing data, we must be able to
extract meaningful information from the imagery
...

Targets in remote sensing images may be any feature or object which can be observed in an image,
and have the following characteristics:
•

Targets may be a point, line, or area feature
...


•

The target must be distinguishable; it must contrast with other features around it in the image

Much interpretation and identification of targets in remote sensing imagery is performed
manually or visually, i
...
by a human interpreter
...
In this case we refer to the data as being in
analog format
...
In
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this case, the data are in a digital format
...
Both analogue and digital imagery
can be displayed as black and white (also called monochrome) images, or as colour images by
combining different channels or bands representing different wavelengths
...
Digital processing may be used to enhance data as a prelude to
visual interpretation
...
However, rarely is digital processing and analysis carried out as a complete
replacement for manual interpretation
...


Manual interpretation and analysis is more recent with the advent of digital recording of remote
sensing data and the development of computers
...


Generally,
•

Manual interpretation requires little, if any, specialized equipment, while digital analysis
requires specialized, and often expensive, equipment
...

The computer environment is more amenable to handling complex images of several or many

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channels or from several dates
...

•

Manual interpretation is a subjective process, meaning that the results will vary with different
interpreters
...
However, determining the
validity and accuracy of the results from digital processing can be difficult
...
Both methods have their merits
...
In fact, the ultimate decision of the utility and
relevance of the information extracted at the end of the analysis process, still must be made by
humans
...
8
...
Observing the
differences between targets and their backgrounds involves comparing different targets based on
any, or all, of the visual elements of tone, shape, size, pattern, texture, shadow, and association
...
Examining satellite images on the weather report, or following high speed
chases by views from a helicopter are all familiar examples of visual image interpretation
...
The nature of each of these interpretation elements is described below, along
with an image example of each
...
Generally, tone is the
fundamental element for distinguishing between
different targets or features
...


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Shape refers to the general form, structure, or
outline of individual objects
...
Straight edge
shapes typically represent urban or agricultural
(field) targets, while natural features, such as forest
edges, are generally more irregular in shape,
except where man has created a road or clear cuts
...

Size of objects in an image is a function of scale
...
A
quick approximation of target size can direct
interpretation to an appropriate result more
quickly
...


Pattern refers to the spatial arrangement of visibly discernible objects
...
Orchards
with evenly spaced trees, and urban streets with regularly spaced
houses are good examples of pattern

Texture refers to the arrangement and frequency of tonal variation in
particular areas of an image
...
Smooth textures
are most often the result of uniform, even surfaces, such as fields,
asphalt, or grasslands
...
Texture is one of the most important elements for
distinguishing features in radar imagery
...
Khaemba W
...
However, shadows can also reduce or eliminate
interpretation in their area of influence, since targets within shadows
are much less (or not at all) discernible from their surroundings
...

The identification of features that one would expect to associate with
other features may provide information to facilitate identification
...
In our
example, a lake is associated with boats, a marina, and adjacent
recreational land
...
9 Remote Sensing Applications
Remote sensed data can be used for a great variety of practical applications, all of which relate, in
general to earth resources
...


Spectral resolution refers to the width or range of each spectral band being recorded
...


Spatial resolution refers to the discernible detail in the image
...
There are applications requiring
data repeatedly and often, such as oil spill, forest fire, and sea ice motion monitoring
...
Obviously,
the most time-critical applications also demand fast turnaround for image processing and delivery
- getting useful imagery quickly into the user's hands
...
Khaemba W
...
Optical sensors have limitations in cloudy environments, where the targets may be
obscured from view
...
Polar areas also suffer from inadequate solar illumination, for months at a
time
...

Often it takes more than a single sensor to adequately address all of the requirements for a given
application
...
Additional
data that can aid in the analysis or interpretation of the data is termed "ancillary" data
...
We do
not touch, for instance, on the wide area of research and practical application in weather and
climate analysis, but focus on applications tied to the surface of the Earth
...
Agriculture
Satellite and airborne images are used as mapping tools to classify crops, examine their health and
viability, and monitor farming practices
...
Forestry
Forests are a valuable resource providing food, shelter, wildlife habitat, fuel, and daily supplies
such as medicinal ingredients and paper
...
Tropical rainforests, in particular, house an immense diversity of species, more
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capable of adapting to, and therefore surviving, changing environmental conditions than
monoculture forests
...
The main issues concerning forest management are
depletion due to natural causes (fires and infestations) or human activity (clear-cutting, burning,
land conversion), and monitoring of health and growth for effective commercial exploitation and
conservation
...

- forest cover type discrimination
- agroforestry mapping

Commercial forestry:
Of importance to commercial forestry companies and to resource management agencies are
inventory and mapping applications: collecting harvest information, updating of inventory
information for timber supply, broad forest type, vegetation density, and biomass measurements
...

- deforestation (rainforest, mangrove colonies)
- species inventory
- watershed protection (riparian strips)
- coastal protection (mangrove forests)
- forest health and vigour
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3
...
It is most commonly understood as the
exploration and exploitation of mineral and hydrocarbon resources, generally to improve the
conditions and standard of living in society
...
Geology also includes the study of potential hazards such
as volcanoes, landslides, and earth quakes, and is thus a critical factor for geotechnical studies
relating to construction and engineering
...
Hydrology
Hydrology is the study of water on the Earth's surface, whether flowing above ground, frozen in
ice or snow, or retained by soil
...
Most hydrological processes are dynamic, not only between years, but
also within and between seasons, and therefore require frequent observations
...
Radar has brought a new dimension to hydrological
studies with its active sensing capabilities, allowing the time window of image acquisition to
include inclement weather conditions or seasonal or diurnal darkness
...
Khaemba W
...
Landcover/ Landuse
Although the terms land cover and land use are often used interchangeably, their actual meanings
are quite distinct
...
Identifying, delineating and mapping land cover is
important for global monitoring studies, resource management, and planning activities
...


Land use refers to the purpose the land serves, for example, recreation, wildlife habitat, or
agriculture
...
This knowledge will help develop
strategies to balance conservation, conflicting uses, and developmental pressures
...


Land use applications of remote sensing include the following:
- natural resource management
- wildlife habitat protection
- baseline mapping for GIS input
- urban expansion / encroachment
- damage delineation (tornadoes, flooding, volcanic, seismic, fire)
- legal boundaries for tax and property evaluation
- target detection - identification of landing strips, roads, clearings, bridges, land/water interface

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6
...
Natural features
and manufactured infrastructures, such as transportation networks, urban areas, and administrative
boundaries can be presented spatially with respect to referenced co-ordinate systems, which may
then be combined with thematic information
...
Integrating elevation information is crucial to many applications and is often the
key to the potential success of present day mapping programs
...
planimetry
2
...
baseline thematic mapping / topographic mapping

7
...
Understanding ocean dynamics is
important for fish stock assessment, ship routing, predicting global circulation consequences of
phenomena such as El Nino, forecasting and monitoring storms so as to reduce the impact of
disaster on marine navigation, off-shore exploration, and coastal settlements
...


Ocean applications of remote sensing include the following:
•

Ocean pattern identification:

•

Fish stock and marine mammal assessment

•

Oil spill

•

Shipping

•

Intertidal zone

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4
...
1 Definition:
GIS is a computer system capable of assembling, storing, manipulating, and displaying
geographically referenced information i
...
Splitting up
the computer system into hardware and software, this definition contains two different fourcomponent-models of a GIS, depending on the point of view
...

Maintaining and editing GIS data: effective storing of spatial and attribute data, data
structures, spatial indexing
Analyzing GIS data: spatial and attributive queries, spatial analysis, intersections
Displaying: map projections, thematic mapping, reports, layout for plotting, presenting
geographic data in the web

In the past, there were many different specialized systems, designed for different tasks
...
The
multiplicity of effort has resulted in the emergence of the general purpose Geographic Information
System (GIS) for which Burrow (1996) gave an all-round definition as:
“A GIS is a powerful set of tools for collecting, storing, retrieving at will, transforming and
displaying spatial data from the real world”
...
Khaemba W
...
2 The components of GIS
Like any other information technology, GIS requires the following four components to work with
geospatial data:

1
...


The computer has a hard disk drive for storing data and programs, but extra storage can be
provided via a network or by digital tape cassettes, optical CD-ROMs, and other devices
...
A plotter or printer is used to present the results of the data
processing
...
The user controls the computer and the peripherals (a general
term used for plotters, printers, digitizers, and other apparatus linked to the computer) via the
computer screen and keyboard, aided by a mouse or printing device
...
GIS Software
There are many different GIS software packages available today
...
Today’s
software packages are capable of allowing both graphical and descriptive data to be stored in a
single database, known as the object-relational model
...
Khaemba W
...
In this model, graphical and descriptive data sets were handled separately
...


The software for a geographical information system may be split into five functional groups
...
Many
tools are available including the interactive computer screen and mouse, the digitizer, word
processors and spreadsheet programs and devices necessary for reading data already written on
magnetic media such as tapes or CD-ROMs
...
The
computer program used to organize the database is known as a Database Management System
(DBMS)
...
Data may be presented as maps, tables, and figures (graphs and
charts) in a variety of ways ranging from the ephemeral image on the computer screen, through
hardcopy output drawn on printer or plotter to information recorded on magnetic media in digital
form
...
Transformations can operate on the spatial, topological, and the
non-spatial aspects of the data, either separately or in combination
...

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GIS designers have realized that the requirements of users to retrieve and transform data are
unlimited
...


3
...

There are several things to consider before acquiring geographic data
...
Errors in the data set can add many unpleasant and costly
hours to implementing a GIS and the results and conclusions of the GIS analysis most likely will
be wrong
...
This should include all dates of the source material and updates and changes made to it
...
The positional accuracy includes measures of the
horizontal and vertical accuracy of the features in the data set
...
This information often includes measurements of some sort, such as
temperature or elevation or a label of a place name
...
It is vital to the analysis aspects of a GIS that this information be
accurate
...
There are several
different mathematical theories and models used to test logical consistency such as metric and
incidence tests, topological and order related tests
...

Completeness – This is a check to see if relevant data is missing with regards to the features
and the attributes
...


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4
...
They include a plethora of
positions including GIS managers, database administrators, application specialists, systems
analysts, and programmers
...
People also need to be educated to make decisions on what type of
system to use
...

•

Viewers are the public at large whose only need is to browse a geographic database for
referential material
...


•

General Users are people who use GIS to conducting business, performing professional
services, and making decisions
...


•

GIS specialists are the people who make the GIS work
...


They are

responsible for the maintenance of the geographic database and the provision of technical
support to the other two classes of users
...
3 Geographic Data: Vector vs
...
Spatial data describes
the location and shape of geographic features and their spatial relationships to other features
...
e
...

The Vector model represents space as a series of fundamental primitives - points, lines and
polygons (areas)
...
Examples include street
lights, wells, telephone polls, missile silos, buildings, trees, species siting (e
...
, in radio-tracking
data), collection site of voucher specimen
...

Lines: results from a set of ordered coordinates that are connected
...
Examples include streets, sewer lines,

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railroad tracks, rivers, flight paths, elevation contour lines
...


Polygons: closed figures that encompass a homogeneous area
...


In ArcGIS, vector spatial data are stored as x,y coordinates
...


Figure 2: Vector data model

In contrast, raster-based GIS programs are made up of cells and groups of cells represent features
...
g
...
The value contained within each cell
represents the value of the geographic feature
...
Much of the data from remote sensing (e
...
, satellites, aerial
photos, etc
...


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Figure 3: Raster data model

Advantages of the Vector representation
Precision is only limited by quality of the original data
Very storage-efficient, since only points about which there is information is or which form
parts of lines and boundaries are stored
Structuring the data logically is very easy
High quality output

Disadvantages of the Vector representation
•

Not suitable for continuous surfaces such as scanned or remotely-sensed images and models
based on these

•

More expensive hardware and especially software

•

Time consuming capturing (digitizing, field surveys)

Advantages of the grid or raster representation
•

Simple concept

•

Easy management within the computer
...
Khaemba W
...
So when combining maps of various resolutions, you must
accept the coarsest resolution

•

Large amount of data especially at high resolution

•

Not appropriate for high-quality cartography (line drawing)

•

Slow transformations of projections

•

Some kind of map analysis (e
...
e difficult to link additional attributes

4
...

e) Compute the size of B (area, perimeter, count of inclusions)
f) Determine the result of intersecting or overlaying various kinds of spatial data
g) Determine the path of least cost, resistance or distance along the ground from X to Y over a
network or a continuous surface
h) List the attributes of entities located at points X1, X2
...


4
...

•

Facilities Management

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Locating underground pipes & cables, balancing loads in electrical networks, planning facility
maintenance, tracking energy use
...

•

Natural Resource-Based

Forest management, wildlife habitat, migration routes management, wild and scenic rivers
preservation, recreation resources planning, floodplain management, wetland preservation,
agricultural

lands

management,

groundwater

environmental impact analysis, viewshed analysis

---