Hello! So, we are going to talk about a very interesting area, which is basic surveying.
And let me introduce myself: I am Dr. Bharat Lohani, I am a faculty in department of civil
engineering in IIT Kanpur, and over the course of all these lectures, I will be talking about
this basic surveying.
What we would like to do: we would like to start there with that; what is the kind of
structure for these lectures is, because I have organised these lectures in a
modular way. Now, what is the meaning of the modular way in this case is, all the lectures are
clubbed in such a way that, if you take one lecture, it is a kind of independent one,
but it will be always helpful if you can go through all the lectures.
So, in all, we have defined around 13 main modules and in all these main modules, there
will be further chapters.
So, a module is basically a major chapter in basic surveying.
So, there are 13 basic structures and in each chapter there will be further lectures 1 to
Now, it will, it is suggested to you, because when you are viewing this video, that you
should view these videos in a series starting from one to the end. So, in all, there will
be around 40 lectures. However, if you cannot do that, you can still manage by viewing individual
modules independently. Because this is how these modules will be designed, the only thing
is you need some background of the previous modules, so that you can understand what is
there in the next module, or what is in the present in a module.
Well, in all the modules, I have to give you some introduction of this. The module number
1 is about an introduction. This is the introduction to the geoinformatics. Though the name of
the video is basic surveying, but I would like to start with this geoinformatics thing,
because geoinformatics is an area of which the basic surveying is the little part. So,
we will be talking about the concepts of surveying in the second module, which will have 4 lectures.
Then, we will be talking about an important area in the surveying, which is the linear
measurement, followed by the compass surveying, where we will have 2 lectures.
Then, we will be also looking into the theodolites and the total stations. These are the instruments
which we make use for angle measurements - a very, very basic thing in basic surveying.
And later on, we will be going for some control surveying that we will cover in triangulation
and trilateration. Then, the seventh module is about levelling and contouring. The seventh
module of levelling and contouring is about basically the control in Z dimension or control
in vertical. There is a very interesting technique of plotting the details in basic surveying,
and this technique is called plane table or plane tabling. In short, we write it as PT.
So, we will cover this in 2 lectures. Finally, all the measurements which you take in basic
surveying, because there is lot of computation involved. We will need to compute a lot, we
will need to adjust for the errors, because all the measurements which we will be taking,
or we will, which we will be talking about will be subjected to some kind of errors.
So we will need to adjust for those errors and this is very, very important module or
the chapter in basic surveying. So please do not miss it if you are following this video
lecture. Well, when we are talking about the basic surveying we must also talk about the
Now in the maps, or in this particular module, we will see: what is the address in India
which can provide you the maps, what are the states at which these maps can be obtained,
what are the prices and where from you can purchase a map. So all this will be covered
in one lecture. Finally, we will talk about the project surveys. There, we will talk about
some civil engineering structure where we would like to apply the surveying. Whatever
we learn in other modules, we would like to apply it there. Then, towards the end of my
video lectures we will be talking about - in 3 lectures - about a technology called GPS.
This Global Positioning System is a new method of doing the surveying.
Well, how I have designed this course’s structure and what is the objective that
I am keeping in mind? Because when I am talking to you through this video lecture, I am thinking
in my mind that you should be able to do certain things: number one, you should be able to
understand the basic concept of basic surveying. You should be able to understand that what
this area is, how to do it, why we do it, what are the techniques, what are the instruments
Another important point: you should be able to apply surveying techniques and equipment
in real life problems. This is very important. If you follow the video lectures carefully,
if you understand each and everything in the video lecture, I am sure you will be able
to apply these techniques and these equipment in any real life problem because, once
you are in a field, you have an actual problem in front of you where the measurements are
involved; you need to apply these techniques. So, my aim of these lectures is so you feel
confident now, at the end of the lectures, that you can apply these techniques.
Another important point, and that is: problem-solving in an optimal way. While we do surveying in
the field there are many possibilities, hundreds of possibilities a single problem can be solved
by. Now, out of those hundreds of possibilities which one is the best one? That is the point.
So, what we have to do is to find a solution which is optimal. Optimal in the sense that:
optimal in terms of the cost, the time, the resources, accuracy and all those things.
So, while doing this course, I will keep talking about these issues time and again. I will
keep informing you about the accuracies which are there, the limitations of the methods,
the strengths of the methods. So, whenever you are in the field, you are going to apply
these methods. You should make use of these things which we are talking in this course,
so that your solution in the field is an optimum solution.
And at the end - this is very important point - that I want you to understand the pitfalls;
the pitfalls of this particular basic surveying. When I say this, I mean: what are the sources
of error? Because if you do not understand this, it might happen that you will end up with:
your data, your problem or your result will come error. We do not want to do that.
What we want: we want to do the work in the most optimal way so we have to understand
that, what are the pitfalls in this particular technique.
Well, so our first lecture today is about an introduction and this is introduction to
the geoinformatics and basic surveying. Mostly today, I will talk about geoinformatics, because
geoinformatics is an area which encompasses many disciplines, many fields, of which basic
surveying is a little part. Because we are going to talk about basic surveying, so we
should know where it belongs to. If you are reading about the basic surveying, you should
know: where you are ultimately going to, what are the modern techniques in order to carry
out basic surveying.
So in order to understand that, we will start with the basics of geoinformatics. What is
the definition of geoinformatics? The definition of geoinformatics is: ‘geo’, ‘information’
and ‘matics’, as written here. So, the ‘geo’ plus ‘information’ plus ‘matics’.
The meaning is: ‘geo’ stands for anything which is on the surface, slightly below, slightly
up of the earth. ‘Information’? Information about those features which are there on the
surface of the earth. Then ‘matics’: ‘matics’ stands for measurements. So we are going to
measure whatever is there on the surface of the earth slightly below, slightly above.
In addition to the measurement, one more aspect of geoinformatics is: that is the management.
So, we measure that information, as well as, we manage that information. So, this measurement
and management of geoinformation, put together, is called geoinformatics.
Well, to start with, we are talking about geoinformation, what the geoinformation is,
we will understand this. As far as the definition of geoinformation is concerned, we can say,
as it is written here: any artificial or natural object/phenomena on, below or above the surface
of the earth. Well, some examples of that: now, here in this diagram, or in this, I can
say in this sketch, what is the geoinformation? You can find the geoinformation in terms of:
the road, or the houses, maybe a tower, the topography, it is here, the jungle - the forest,
a water body, the hedges, a playground, another playground, or maybe some house, and the field,
some other land use or land cover. So, this is all the geoinformation. So, whatever is,
whatever you see on the surface of the earth, or we also know, slightly below it or maybe
slightly above it, is the geoinformation.
Now, for this geoinformatics, generally what I do, I try to define geoinformatics in two
basic divisions, because this is very important in order to understand geoinformatics.
Whatever we will be doing henceforth, we should understand these two philosophical divisions in the geoinformatics.
What these two divisions are: number one is measurement of geoinformation. We need to
measure what is the geoinformation because we have to see what the geoinformation is,
as a thing on the surface of the earth. So, we need to measure it.
But in measurement also, there are two parts. This is very interesting and very fundamental,
so we can understand this.
First part in measurement of geoinformation is geometry. We want to
see what is where - we will explain it by an example in a moment. Then, we also want
to know that, what is what. That is, the identification.
Here is an example: well, let us take - this is the terrain, or the ground, and on that
ground there is a certain object. Now - this is the geoinformation here; this object is
Now, we want to measure the geoinformation. What is the meaning of that? The meaning of
that is, we need to define a rectangle system like the coordinate system shown over here
and we need to face the coordinates of this – of this geoinformation, this feature.
So we want to measure the X, the Y and the Z, so the moment we read the XYZ in our reference system,
the geoinformation is measured. But measurement is not enough. It is not enough
because we need to also do another thing that, what we have measured - what is there on the
ground, what is the feature? So we need to go for the identification.
Now, what is the meaning of the identification? Identification means: what we have measured.
Is it a tree? Is it a road, or is it a house, or a garden, or a hedge, or a boundary wall,
or the hill, or the river? So we need to identify this also. So basically, whenever we are talking
about measurement of geoinformation we will be doing these two things: number one, we
will be measuring it in terms of a coordinate system.
We will fix the XYZ coordinates and the second thing that we will do, we will try to identify
that what we have measured.
Well, the second aspect of geoinformatics - because I was saying that geoinformatics
has got two fundamental divisions; one is the measurement of geoinformation - the second
one, second one is about, well, take it like this: we have measured the geoinformation,
we know the XYZ coordinates of a particular feature, we also know what the feature is,
but what to do of this? What to do of this information? So, the second aspect of geoinformation
is - or the geoinformatics is - Management of Geoinformation. As we have written here
in the slide, we want to manage the geoinformation because just measurement, identification is
Now for example here, if you look at the slide, here in the previous slide, we are talking
about the measurement of geoinformation and now, here we are talking about the management
The management means, all the things which we have measured, we have identified,
we are trying to plot them here - and if you see in the slide - using a map. So we are
detailing them for our use later on; we are storing the data in a particular format. What
we have done - for example, in this map, we had measured where is the ground, all the
roads - where they were, we also identified what are the roads, where they are leading
to. We also identified where are the fields, we also identified where are the areas which
are occupied by houses. So our measurement and identification was complete.
So, the management of this information means: we want to put this information in such a
way, so that we can store it properly. Not only storage - we want to retrieve this information
later on, so the retrieval. Now, with this map, what all we have done - we have stored
the information in the form of a map. Anytime we want to know about the map; we want to
know about the geoinformation, what we need to do, we just take the map out and start
looking at the features. So what we are doing? You are retrieving the information from the
And then, the presentation - of course, the map is a way of presenting this information.
We could have presented this information what we measured there in the ground maybe in some
other way also - for example, the names of the roads, their lands - so you could have
made a table. So, that is also a way of presenting this information, or maybe managing this information.
But our information here is the geoinformation – ‘geo’ means ‘which is expressed
in the terrain’. It is a spatial information, so we want to present it in such a way so
that information retains its own characteristic; that the information is presented also in
a special way, and this is how this map come into the picture.
Now, another aspect of management of geoinformation is manipulation. Now, as I am writing here
in the slide, manipulation is: analysis of geoinformation so that we can come out with
some results; some answers.
One example here could be: as we can see in this map, let us say, I want to start from
the particular junction in the town, and I want to reach the other junction here in the
town. Well, throughout this street network, there are various possibilities: you can change
the route, well, like this, or you may like to take a route like this But the question
is, which of these two routes is bad. So what you need to do, you need to analyse this information.
You need to do some kind of network analysis in your information. So that is also a part
of Geoinformatics. So what we do in geoinformatics: we measure
the geoinformation from that field - we measure it by recording the co-ordinates
XYZ - and we also identify that information that what we have measured. Then, we come
to the office, we present the information; we will store the information in such a way
- either in the computer or in the form of the maps - so that you can retrieve it later
on, you can present it in a proper way and also, with the help of the information, we
want to analyze the information so that we can arrive at certain result. Well, having
said that - as I was saying that - we have to measure the geoinformation and we have
to manage the geoinformation.
So what I will do, I will give you a brief introduction of the tools which we use for
measuring geoinformation, and then I am talking about this - we will talk about this - measuring
tools for geoinformation in the way they were developed. So we will start from the very,
very primitive time, how people used to measure it; and we will come to the latest stage,
that how we are measuring the geoinformation now.
Well, initially, the primitive techniques: as we all know that still, if you go to the
villages you will find people doing it.
You use either pace - pace means you walk along it - or maybe use the hand, you know,
you could ball it - okay, a particular land is so much. You will make use of your hand,
then you measure it. Or maybe you can make a guess, or maybe you also make use of some
rods - some standard rods - so these are the primitive ways of measuring the distances.
There are some very good examples in Vedic-age methods of pacing. I’ll give you one example
right now, and for that I will need to change the slide.
So we are here in the new slide, and what did the Vedic age people used to do? I will
give you just one example of this pacing: let us say this is the ground, and we would
like to measure the quality of the soil. So what they would do, they would dig a hole
there in the soil - or in the land - and they will fill it with water. So this hole has
been dug and the soil is cut out and now, it is filled with water.
Now, in order to measure the time what they would do: a person who is doing this job,
or maybe another person, will walk to this side - for example, let us say a hundred paces
- so he will do this pacing hundred times. He is at a certain distance and from that
point he will come back. While he comes back, they will check again that where is the water
level now. Depending how much the water level has gone down, they will come to know about
the soil. So basically why I am talking about this - I am talking about this because the
people were making use of pacing - measuring distances, measuring time using the human
body - in Vedic age also.
Now we go back to our previous slide. So we talked about this: just one example how people
were making use of the human body for measuring distances. Another one you must have seen
in villages - this is very, quite common. The Patwaris, who are the grassroot level
worker in a village who measure the land there - they also make use of some devices, maybe
in form of a rod or some chain, in order to measure the land parcel. So that - it – that
is also - you know, I would, I would like to say - quite a primitive way of measurement.
Then, if you further go into the villages, still, people they measure their land area
using, for example, the ‘nali’ and ‘haath’. So these sounds may differ - I am writing
nali and haath because the area from where I belong to, people use this. ‘This particular
area is one nali or two nali’ - that kind of thing. Now, how it is related with the
area of the ground is, how much wheat or rice will be produced in that particular area.
So this is how a relationship is there in how much wheat is produced for a particular
period, and this is how they are coming to know about the area.
So, what we observe in most of these cases: the human figure was used - either the face,
the hands or these things.
Now, after some time, when people started requiring accurate measurement, what they
thought - that the human body was not good enough, because all humans, they differed
in the measurement. So if, for someone, a distance is hundred paces, for other person
who is short in height, the distance would be hundred twenty paces. So they wanted to
standardise these things. So some new methods came for making these measurements. So, that
was the time when the land surveying - measuring the lands - started.
So the extended methods of measuring distances are: chain or maybe tape; at the same time,
people also wanted to measure the angle because in order to determine the area, you also need
the angle. Here is an instrument which is called compass – it is a very simple instrument,
and it works on the principle of magnet - magnetic needle. So there is a magnetic needle which
will align itself in the magnetic field, and making use of that, it is possible that we
can measure the angle. So people started making use of compass also.
Some more instruments - for example, the theodolite. This is also an instrument which is used for
making the measurement of angle in a more sophisticated way; more accurately. However
the problems with the land surveying methods was: in most of the cases these methods are
As I am writing in the slide, they cannot be done in inaccessible areas, so that what
we need to do: you need to go to that area and you need to occupy the point, then you
need to carry out the measurements. So all these methods are kind of, very, very cumbersome;
they will take long, long durations in order to complete the survey.
So considering this time, people have started thinking of some other methods.
So, the other methods came in the same form of land surveying, but with the development
of electronics. What people started doing, they converted these instruments, which were
conventional mechanical instruments earlier, into the electronic instruments. As it is
written here ,we have the methods now which are mostly relying on the instruments
which make use of the electronics, and in this case we have the instrument, for example, the EDMI.
It is an electronic distance-measuring instrument. Now to measure the distance, you need not
do the pacing, you need not spread the chain; but what you need to do, you need to simply
fire an electromagnetic pulse and it will tell you the distance. So these instruments
are very very sophisticated.
Also, as seen here in the slide, we have a total station. This total station can measure
angles, can measure distances - all automatically, without much involvement of the human being.
So now the things are become very, very fast -it can do a very accurate survey; it can
do them very fast. Here is another word which is seen in the slide: it says robotic Sometime
back, the total stations were like that, that a human being has to operate it. But now,
total stations are developed to such a stage that the total station is kept in a place independently,
while the surveyor moves with the rod - which is also a part of the total
stations - everywhere in the ground. Total station will target that road automatically;
the surveyor who is moving with the rod will just press some buttons, and with the press
of those buttons the total stations will carry out the measurements.
So it is really very fast - a single person can do the surveying. However, in these electronic
methods also, as you see in the slide, they are still difficult - difficult because you
have to go to the ground, you have to occupy the point. I will give you one example: let
us say you want to measure for a power line. This is the power line between two poles.
You have to measure the coordinates of several points there in the power line. If you need
to do it, using the total station is a very difficult exercise because you need to bisect
Then, another example: if we want to measure, let us say, an area which is flooded, it is
very difficult to go to that area; you cannot occupy the point there because, as you know,
it is flooded. So you cannot carry out the measurements. What you need to do, you need
to wait so that the flooded water level will recede, then we will go to the ground, occupy
the ground, then carry out the measurement.
So in all the methods that we saw so far - either the primitive ones, land surveying ones or
the electronic surveying ones - in all the cases, you have to go to the ground, occupy
the ground, and then take the measurements. So this is really difficult in case of difficult
terrain; in case of inaccessible terrain. So considering this, people started thinking
of something more; some new measurements to escape from measuring the geoinformation.
And here is one which I am writing in the slide, that is, the aerial photogrammetry.
As you see here in the picture, in case of the aerial photogrammetry, once it was developed,
initially - during the time of world war one and two - people used it for flying purpose.
What they would do, they would fix a camera in the body of the pigeon, and the pigeon
will fly in the enemy terrain, and it will take a single photograph and it will come
back. So it was a very nice way, a very smart way, of taking the photograph from the air
in this enemy area so we have all the information about the enemy movement. So this is how the
aerial photogrammetry developed.
However, later on, we have started making use of balloons and, as well as, aircraft
based. What we do now, I am going to give you an example in the case of the aircraft.
The aircraft will fly at an altitude of, for example, 2000 metres, 3000 metres, 4000, 10000
- depending what kind of application, what kind of photograph we are looking for. So
while the aircraft is flying over the ground, it will take an image; it will capture one
photograph of the ground.
The aircraft moves further; it will capture another one. So, like that, a series of photographs
will be captured for the terrain, and these photographs we say ‘aerial photograph’.
As you can see here, in these aerial photographs, we have some areas which is overlapping. We
will make use of these in a moment.
Now this is a photograph - could be either a single photograph as you see here.
This is a single photograph of the terrain, and you know, in this you can see the road,
the vehicles on the road, houses, the trees, some water-pond; so we cannot identify the
same - one aspect of geoinformation.
Not only that; if our photograph are stereo - stereo means, as we are talking in the earlier
case, two overlapping photographs from two positions of the aircraft - we have the area
which is common in two photographs. So that kind of photograph - this photograph and this
photograph put together – this is stereo pair. So, if we have the stereo pair or the
stereo photographs, is it possible to generate three-dimensional model of the ground.
Now, once you can generate a three-dimensional model of the ground - what is the meaning
of that? The meaning of that is: you can now start measuring on that 3D model various things
- you can measure the distances, you can measure the coordinates, you can measure the angles.
So with the help of the photograph, as you are looking here, you can measure the XYZ
coordinate, you can identify the things, so we can get our all geoinformation that we
This aerial photogrammetry also developed like anything - earlier we had some analogue
way of taking the photograph, also processing them; in between changed to analytical way;
and now the modern one - just for your information - is the digital photogrammetry. Well, most
of the things are automatic now. However, as we are writing here, still we need to fly
to collect the data every time. Whenever you need the data, we need to fly with the aerial
photograph and this is not always possible. Why it is not possible? Because, for example,
some area is flooded and you need to take aerial photograph of that area because
you want to see how much of the area is flooded; you want to take the Measurements.
So, in order to measure this, you need to fly using the aircraft. Now the problem: the aircraft
may not be available or the aircraft, where it is available, may be very, very far from
the side where the flooding is taking place. So it is really very difficult to fly every
time - you cannot do it immediately in many instances.
The second thing: even if you can fly every time, it is a costly affair; the aircraft
will cost a lot, the crew will cost a lot - so it is a costly affair. So, though the
aircrafts were able to give us very fast, very accurate and very, very synoptic- everything
on the ground – geoinformation, we had some limitations from the aerial photogrammetry.
Aerial photogrammetry - it is being used now depending upon the application, but people
started thinking something more: well, can there be something in the space which can
go around the earth; can take the observations regularly? And the idea of satellite came
So, the satellites are such things: as you can see in the slide, they will rotate around
the earth. They will keep rotating around the earth and they will keep taking the images
of the earth. They take it because while the satellite is rotating - it is orbiting - the
earth will spin. So it is possible that the images are taken all over the earth, everywhere.
So what do you have? You have now the system which can take the images repetitively -
after five days after ten days - depending upon the satellite.
So this satellite remote sensing, it actually started – commercially, I’m saying, because
there were some 5 satellites earlier also; the data of those satellites was not available
earlier with the civil users. So the commercial remote sensing, it in fact started in 1972
with a satellite that was called Lansat - sorry about that - Landsat. That was a satellite
by United States, and this data was available to the civil users.
Generally, these satellites, which we use for the earth observation, they will be from
600 kilometres to 900 kilometres altitude. So, from those altitudes - you just think
of that, you know this is a very, very high altitude - the satellite is orbiting there,
and you are going to capture the images of the earth.
So, what you capture from the satellite may be a case like this. Now here in this, a satellite
has captured an image of European country, while you can see the Africa also there - the
north part of the Africa - you can see the United Kingdom. Part of the Europe is in dark
because it is an image of evening time. Part of the Europe – here in the UK; the London,
the Ireland - they are still towards the evening; it is not dark there, while in the other parts
– the France and other parts - you can see the lights on.
So, satellites which are at very high altitude can capture images like this. Now this kind
of view of the satellite, because it is capturing, in one view, everything, whatever is there
- I mean huge area - we said is a synoptic view of the terrain. But this kind of view
was not possible earlier. If you are doing land surveying, if you are doing aerial photogrammetry
also, this was not possible. Then, the second aspect: satellites also take images in several
wave bands. What is the meaning of this? The meaning is, it does not take the image only
in optical; it can take images, it can take the photograph or the imageries also in microwave.
Now, if there are some cloud covers over the area - for example, let us say, in this slide
there are some cloud covers; these are the clouds. If we are taking the image in optical,
then because of the cloud we cannot observe the ground. In the satellite image, we will
have all the cloud. So if you are using - if you are using the microwave remote sensing,
it is possible that you can see beneath the clouds.
So, there is a term called spatial resolution in satellite remote sensing. Earlier, the
satellites - the commercial satellites also - they had a spatial resolution of 80 metre.
Now, what is the meaning of that? To understand the meaning of that you need to see this slide.
In this slide, it is a synoptic view - we can see the entire continent, but we cannot
see the individual spaces; we cannot see the individual houses, so the resolution of data
is very poor.
However, in this slide, as you see, we can see the individual car on the road, the houses,
bridge, maybe some more homes, some more cars, individual trees -everything is clearly visible.
Now this is the data from external satellite - the resolution of this satellite is 1 metre.
So we have, in commercial arena, some satellite which can give you the resolution varying
from kilometre to metre - it depends, what kind of your application is.
If your application demands huge areas, big areas, then you will go for resolution in
kilometre. Your application is something like, you know, forest mapping, you do not want
to measure each and every tree. The area – you, you want to measure the entire acres of the
forest, so it is advisable not to go for a data which is very accurate; the resolution
is only 1 metre or half a metre. But if your application is: you want to measure the individual
car on the road, you want to measure the outlines of the building, you have to measure where
exactly the trees are, you want to measure what is the outline of the river - exactly,
So, for most of engineering applications, we need accurate measurements. So it is possible
that we can get these accurate measurements with the satellite which has a spatial resolution
of order of 1 metre or slightly around. So we have, at the moment, the best resolution
commercially available of around half a metre. So it is a very, very good resolution; we
can see many details, a lot of information in the data.
Now this satellite data also - because we are talking about - I will take you back again
to where we started with. We started with the Geoinformatics - basically two divisions:
measurement of geoinformation and management. Then in measurement of geoinformation again
two things: where the information is, that is the XYZ co-ordinate, the second thing:
what the information is.
So we can make use of satellite data - as you can see in the slide - for both the purposes:
we can do the measurement here and also we can do the identification. Well, you can identify
in this figure the bridge, building, road, car, everything. You know, this same process
which we do in remote sensing, it is possible that I can assign co-ordinates also to each
and every point - not only X and Y but also Z. So by that measurement, you know the XYZ
co-ordinates also of each and every point. So if you want to measure the distance along
this road, the distance is known to you. So now see how the things have changed: earlier
we were supposed to go to the ground, occupy this point; but now we are not going to the
ground, rather, we are making use of satellite image, and using that image - satellite image
- you can measure the distances. You can also measure the angle, for example the angle between
these two streets; what this angle is. So we can make use of satellite remote sensing
for both measurement and identification.
Another interesting thing - I just wanted to show you because this is very important
data; the satellite will take repetitive data. As I told, they will cover your earth every
fifth day, ninth day, eighteenth day, twenty second day, depending which satellite we are
talking about. Here is the data from Digital Globe. The name of the satellite is Quickbird
and the resolution is half a metre. This is the data from Indonesia and this is the data
just before the tsunami of 26 December 2004. So this is the area which was - the area used
to look like this before the tsunami with houses, fields, the trees, more fields, houses,
Now, after the Tsunami, again the satellite recaptured the data. Now how the data looks
like - the data look like this. Wow! Here and here, both are same. So we can see the
area which has been flooded now, so you can do this mapping very quickly, using the satellite,
of all the areas which have been flooded. You can also make use of this data in order
to see the damages to the buildings. All the buildings have been damaged. One little building
over here - still the roof is intact. So you can guess that this building didn’t damage
while for all other buildings, they have been damaged. You can see the debris - everywhere
the debris is falling. So this is how, you know, we can make use of satellite image in
order to collect geoinformation - about measurement of the geoinformation as well as … management
we will talk later on. But for geoinformation; knowing where it is, also knowing what it
One more modern tool - this is the modern tool which we say the GPS; Global Positioning
System. Now what this GPS is: we saw in the beginning itself, we always wanted to know
where we are. Okay, in the Vedic age also, people found some ways to know where they
are - they made use of the stars, the sun, the moon and all those things.
We wanted to know our location because our location is very important to us; because
I want to see what my location is in relation to other things. So the GPS is the instrument
which can give best location very accurately
What the GPS is: in the case of the GPS, as you can see here, all around our earth we
have around 24 - I am saying 24 at the moment though it is not exactly 24, it is more than
that - number of GPS satellites and these satellites are orbiting the earth in such
a way that at any moment of time, if you are standing anywhere, you can see at least 4
satellites - of course, more than that. What do you have? You have a receiver - a receiver
of the GPS may look like this or maybe it will be a simple handheld device like the
This receiver measures your distance to 4 satellites, as you can see here. There is
a method - we will see this method later on. So by measuring these 4 distances, also by
knowing the location of these satellites - exactly at the time when we are measuring the distance
- in a coordinate system which is defined at the centre of the earth, it is possible
for us that we can determine where this receiver is.
So wherever you go on the surface of the earth, you are standing here and using this GPS receiver,
you should be able to determine where you are in this coordinate system. It is a very
good instrument - that little instrument which has the size of only a mobile phone.
You go around with this anywhere; if you are walking with this instrument, it is possible because
the receiver is measuring the distances to four satellites and immediately, by the computations,
I will come to know where I am; what are the latitudes, longitudes and altitudes of the
point where I am standing. So anywhere you go around the earth, this is possible.
Now what you can do? If you know the latitude of this place; of this place - all the coordinates,
latitude, longitude and altitude - of two points on the surface of the earth, you can
measure the distance between two points; if you know the lat, long and altitude of the
third point also, you can also measure the angle .
Well, one more point, you can find the area. So now with this - a single GPS - as you move,
your coordinates are being measured automatically and independently.
So you know the co-ordinates of this point, co-ordinates of this point, co-ordinates of
this point, co-ordinates of this point, and if you know the co-ordinates of all these
points, the area of this field is known to you. So it is very interesting way of carrying
out the measurements and a very, very modern way.
Now, as you are seeing, there are at least 24 satellites which we need to make use of
and the coordinates are given. I am going to give the term here; it is called geocentric
coordinate system. The meaning is: the centre of the coordinate of the origin is at the
centre of the earth. So all the coordinates where we are going with the GPS receiver will
be measured in this particular coordinate system.
Now, about the global positioning system: it is very fast if you want to take slightly
less accurate measurement. Okay, you can just run - you can - you are in a car, you are
moving in a car, and the GPS with you which is in the car is looking at the satellite,
measuring the distances to the satellites and finding the location.
If you want to do it very, very accurately, say in millimetre level; you want to do it
very accurately for some applications, for example in the case of the earthquake, where,
let us say I am drawing this diagram - this is a fault, and there is likelihood of a movement
along this fault. Let us say I draw it this way.
So we need to monitor this fault - if any movement is taking place there. So what people
are doing now, several distances they are putting the GPS - GPS 1, GPS 2, similarly
here also – 3, 4 and so on. So what we have, we have a network of GPSs set along - all
along the fault line. So we have the network like this. Now, if there is any relative movement
in between these two plates, so these points will move in relation to these
two. What the GPS is giving us? GPS is giving us the coordinates regularly. So we know the
coordinates of this, so we know this distance, or rather I can say we know this vector. So
between two points, I know the vector.
Now, this was my initial vector. Now, this initial vector may change after some time.
So, this change in the vector in terms of the angle, in terms of the distance - it is
because of the relative movement of these two plates. So, people are trying to make
use of this kind of observation - the GPS observation - in order to predict the earthquake.
Now another thing, another good thing about the GPS - you can use it everywhere, all over
the earth - wherever you can find open sky. You can’t do it inside the room because
you need to see the satellite.
So because it gives you a location, there are thousands of applications which are possible,
and many more applications are being invented. GPS is going to be an essential part; in many
mobile phone models the GPS are there. Even in many watches - people are wearing the GPS
in their watch. If someone is going to a forested area; they want to go to, you know, they want
to go to a forested area - so there in the forest, they want to locate where they are
moving. They carry a handheld GPS of the type of a mobile phone and it keeps telling you:
okay, you are moving in this direction. If you want to come back, look at the movement
how you had reached a particular point - so you have to just backtrack. So all these things
are possible with the GPS.
Now having seen all these, as initially I taught, for the Geoinformatics, there are
two fundamental divisions: one, measurement of geoinformation. Now whatever we have discussed
so far - the primitive techniques, land surveying, electronic surveying, aerial photogrammetry,
satellite remote sensing or the GPS - all these are the methods for taking observations;
for measuring geoinformation. Also, all these are the methods by which we can not only measure
XYZ of the geoinformation, but we also know about what they are.
Now, the next aspect: once you have measured this information we want to manage it, we
want to store it properly. So, that is the second aspect or the fundamental division
of geoinformatics area, which is the management of geoinformation. So, as we saw a little
bit earlier also, we need to store our data - there is a requirement to store the data,
there is a requirement for retrieving the information. You have to store it properly
and whenever we need it, we need to retrieve it; we need to get it back. So, that is the
management of the geoinformation.
We also need to present the information. What is the meaning of that? Whatever you have
accumulated, whatever we measured in the field, you need to present it. Maybe you want to
make a map, maybe you want to make a table, may be you want to make an action - you know,
you want to give to a leader, a political leader - you want to show him, okay, how much
of the area is flooded; he is interested in that. So what you do, you use the map of the
town - on top of that you want to draw a line which shows the area which is flooded. So
that give information presentation.
So, that is also a part of the management of geoinformation. Most important of all - because
storing, retrieving, presentation these are all important aspects - but the most important
of all is, whatever geoinformation that you stored with you, you want to analyse it. You
want to put all the information together so that you want to come out with some kind of
One thing could be - one example - let us say we have a map of an area, and in that
map we have the topography zone - I am just drawing it this way right now - we have some trees,
here, the houses - everything - here some villages here, you know, having the houses
and all that - fields, pools, river – everything.
Now your job is, you want to start from a point A and you want to reach point B - so
far there is no road in between A and B. So what you do, you want to join A and B by a
route. So there are various possibilities: you can join them by a road which may go like
this, you can join them by a road which may go like this Which way? What is the best way?
So what you do, you make use of the geoinformation which is collected. So, for a problem like
this, the geoinformation could be the geology of the area, the rock types, where the villages are,
where the trees are, where the streets, where the schools, where the towns - all this
is the geoinformation. So you put all this geoinformation together, and then your computer,
where this information is kept, analyses this in order to find the best possible route alignment
between these two points A and B. So that is an aspect where we do analysis of the geoinformation.
Now, in geoinformation there is a term which is called GIS. GIS stands for Geographical
Information System, and this GIS does all this management part; whatever we are talking
about. Everything will be covered in GIS.
Now, I would like to end this presentation by one example of the GIS, and this is - the
example is - there in some town where there is the flooding, and we need to locate the
area where we need to provide the relief. This is a very important decision - we want
to provide the relief in those areas where it is required. Now this is the problem; now
start thinking - in order to answer this problem to provide relief to those areas where it
is flooded, what all information you need; what all geoinformation you need? So the geoinformation
that we need: okay, how much area is flooded? We need to measure it. How do you measure
it? We can make use of the satellite or you can go to the ground if possible and map it.
We need - because we have to provide the relief - we need to know what is the road network
in the area and what are the types of the roads.
What is the chance that a particular road have been washed away? We need to know about
the topography – why topography? We need to know about the topography because, those
areas which are elevated, if we know that the stage of the river or the height of the
flood water is so and so. So we can make an assessment - what all areas will be flooded
- if we know the topography of the land. Topography means the undulation, so those areas which
are higher will not be flooded. We need to know about the pakka houses - if you know
about the pakka houses - the school building, any government building there - so we know
that these are the buildings which will not be damaged, so the chances are people are
occupied in these buildings, because these are not damaged. Okay, so distribution of
where the one story and multi-story houses are - we need to know the probable shelter
where the people are going to stay in the event of the flood.
So having known all this information, there is a requirement now to take a decision
where all these information will be put, and a decision will be taken on the basis of this
geoinformation. So what we need to do, we need to put all this information in a model.
Now this model will run under GIS, which will make use of all these information to find
the sites on priority basis for the rescue. So we need a model, and that model can be
run on this GIS data; the geoinformation. So this is the management part of the geoinformation,
where we are coming out with the areas – there, this is the area where the relief has to be
This task, if we do it manually is a very difficult task, so manual interpretation is
involved and conventional methods are involved, which are very, very difficult to carry out.
So carrying out this task in a computer in the GIS is suggested.
Now finally, whatever we have done today, in our next video lecture, we will talk in
detail about the basic surveying. Because today we saw that what the geoinformation
is, what is geoinformatics, and tomorrow we will see what the basic surveying, though
we saw about it a little bit today. So this is what we will cover in our next
video lecture. Thank you.