Module – 1 Lecture – 1 Surveying

Module – 1 Lecture – 1 Surveying


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 5. 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 maps. 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 and everything. 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 the geoinformation. 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 not enough. 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 of geoinformation 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 map. 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 very cumbersome. 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 every point. 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 need to. 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 in mind. 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, very accurately. 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, the jungle. 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 is. 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 mobile phone. 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 final answer. 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 provided. 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.

Posts created 35462

86 thoughts on “Module – 1 Lecture – 1 Surveying

  1. Complete waste of time! This is like the time when teachers expected students to memorize answers and regurgitate them at exams. If you go to MIT's Open-Courseware, you can actually learn some useful skills. What a waste of time, effort and public money by IITs and IISc!

  2. I found it very useful.I think I should also watch useful IIT videos being here in Nepal.
    Thanks IIT and Dr Lohani for publishing publicly.
    YRS
    Nepal.

  3. thanku thanku thanku so much sir DR. Bharat Lohani and your whole team.
    really its so much use full for me and other students like me..
    Insha Allha.
    please upload more videos like this only.

  4. It's the best video for all the civil engineering student thank you sir we appreciate you sir

  5. Sir, Module 8 Lecture 1 Surveying is corrupted, I am unable to download it. Will you please send me fresh link for Module 8 Lecture 1 Surveying?

  6. Indian professors ("lecturers", excuse me) talk funny when they speak English, don't you think?

  7. Wow…..what a way of teaching…..U r great sir…this lecture is very useful and presented in a very simple way…..thank u sir for this lecture

  8. Sir your leacherar of surveying only.. Sir you very nice teacher & you r parectly solved problems in surveying. U have know that other some subjects teacher teaching in Civil Engineering. Can u recommend some teachers in Civil Engineering.

  9. Youtube comments are full of amusements sometimes….
    https://chrome.google.com/webstore/detail/threelly-ai-for-youtube/dfohlnjmjiipcppekkbhbabjbnikkibo

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