Hello everyone and today in this introduction to remote sensing course this is 12th lecture
and we will be talking about how remote sensing can be integrated with the other 2 powerful
technologies GIS that is Geographic Information System and (gl) Global Navigation Systems
one of the example is GPS but we will discussing also some other navigation systems as well
As you know that in earlier lectures also I have mentioned that GIS GPS and remote sensing
are having 3 common things in between that they are generic technologies that means they
can be applied to various areas application areas and there are few areas still unexplored
so in future we will be seeing the applications of these technologies either in a integrated
fashion or may be individually or maybe 2 technologies together maybe in some more new
technologies may come in between but the 3 common things are generic so that they can
be applied for various applications
Spatial which are related with the location specific data because remote sensing images
provides the data of a particular part of the earth so it is having location same in
your GPS GPS provides the geographic coordinates and GIS provides a platform to handle all
kinds of spatial data so therefore these technologies we put them as a spatial technologies as well
and finally and the third common thing between these technologies is digital
Digital means originally the remote sensing data is collected in digital form transmitted
in digital form and now there are digital platforms computer or image processing softwares
are available so we can digitally process the data interpret the data and analyze the
data according to our requirements Same with the GPS GPS data is also available in digital
format and GIS again the platform which provides to handle all kinds of remote sensing and
GPS data so these 3 common commonalities between these 3 technologies have allowed us to create
new types of applications new types of products
One of the very popular products which nowadays we are using is like Google Map or Google
Earth which are using remote sensing technologies like Google Earth as well as digital elevation
model which has been derived from remote sensing data and say on and you say custom design
GIS software and if you are having GPS input collected from some location field surveys
especially for civil engineers then that too can be put on that one on Google Earth so
it’s a wonderful product which is a integrated product of GIS and (remo) remote sensing plus
you can add the your input data from GPS as well during field surveys
As you know that GIS because GIS has not been introduced in this course but there is a separate
course which I have delivered GIS but just for completeness that I will bring the just
definition of GIS which is a computer based information system designed to accept large
volume of spatial data spatial data means location specific data objects which are having
geographic locations and that data might be coming from variety of sources and the purpose
of GIS platforms are to efficiently store that spatial data and retrieve retrieve as
per user requirements analyze it and model it So that we can we can analyze to that extent
that we start predicting about some phenomena some features or for for exploration purpose
or any other purposes so model N then finally display or create outputs as per user defined
specifications So that’s the purpose of GIS which allows us to handle all kinds of
a spatial data on a digital platform
The data might be coming from variety of sources it also allows you to convert analog data
into digital data to some extent in a semi automatic manner and then you finally integrate
everything and start creating new products The important point here that the these are
the few terms we we use interchangeably sometimes anonymously but in fact if we start looking
in details that these are all together different words different terms have got different meanings
For example data and versus information The data is basically about the raw facts the
data is nothing but a raw facts and by itself (gene) generally from the information and
suppose somebody has got the data about some surveys which has been done in the field and
just fed in the say excel sheet Now it till then it will remain the data no analysis has
been done no other processing has been done but once I start doing some analysis simple
may be statistical analysis may be some sorting things
Suppose somebody has gone in the field collected water sample data Now if he has collected
30 samples from different areas then I want to see the distribution so I will try to plot
the map on the on GIS platform a form of map using geographic coordinates and this will
start giving me the clustering information and other things whether the data has been
collected uniformly or collected from only in a small area and so and so forth plus also
that what is the highest value that data which I have collected what is the lowest value
Suppose value I talk about PH so where is the PH highest on the water and where is the
less so once you start analyzing these things on the raw facts that is the data then your
data is converted to information
But before that just collecting the data from the field and putting into say excel sheet
or database it doesn’t become that information it has to be analyzed certain kind of operations
analytical operations statistical operations have to be performed on that and once these
are done then this data can be converted into information So these are 2 terms this we have
taken completely differently Data as I mentioned that data is itself little use unless it is
transformed into information and the today is the computer technology is allowing us
to transform these raw facts the data into information quite easily and information is
the answer based on raw data
We create questions once the data has been analyzed it it is converted to information
Now when we raise the questions for example I can raise that where I have found the minimum
PH value in the water samples where I have found the maximum PH value what is the average
PH value or in which areas if I have plotted this location then in which area I am getting
higher PH value in which area so all kinds of questions Once the data has been converted
to information can be answered various types of questions may not be all kinds of questions
so but the GIS goes on step forward it converts your data in not only into information but
also into the knowledge
That we will see here now that first is the (ro) the (ro) raw facts or data using computers
we can convert this into the information but when when we use the GIS platform along with
some other information’s may be remote sensing data or maybe some other maps may be soil
map or a elevation map or some other thing then I can convert that into the knowledge
and this becomes very (power) that is why GIS becomes a very powerful tool so that the
raw data by its self analysis and further processing can directly be converted into
knowledge and that makes a lot of utility of GIS otherwise simply using computers maximum
you can do you can convert into information but using GIS you can convert to knowledge
Now the third technology this is GPS as we know that GPS was invented the early 90’s
or well it came in the civilian domain the early 90s when there were war between Kuwait
and Iraq and American army entered in that war from the Kuwait side and what happened
then they started because they were (wa) doing this or they were having war in a desert area
and landmarks are very difficult to find so using just simple topographic sheets it was
very difficult So why that but before that they developed this technology mainly for
army purposes and that was the navigation system and they gave this name a Global Positioning
System
Earlier it used to called strategic defense initiative or (pa) it was part of Star Wars
of Ronald Reagan Parallelly also when the Americans were developing GPS which is known
as GPS parallelly Russians were also developing and that system is called Glonass and they
both systems are Global Navigation Systems but GPS came first and it it was allowed by
the to use by the civilians and therefore it became very popular And still today even
in our mobiles we are having GPS receivers hand held GPS receivers and much more advanced
versions of like (differ) a differential GPS are available today and in in civil engineering
especially in surveying extensively these things are being used
So basically if we look the definition of GPS or any navigation system basically it’s
a network of orbiting satellites that sends précised details of their position in a space
back to earth and these signals are obtained by GPS receivers such as navigation devices
and are used to calculate the exact position a speed time and the vehicle locations Concept
wise it is simple If you look the earlier surveying methods we used to if wanted to
know where we I am located on a map then we what we used to do we take we used to take
back bearing during our field service from 2 knows points which are which I can see from
my naked eyes in the field itself and the same corresponding points I can also locate
in my toposheet
So then we used to take back bearing from these known 2 points which I which I am seeing
and at the same time I am seeing in toposheet and then drawing these lines So wherever these
lines used to cut we used to say that we probably we are located here in order to make certain
that we are there exactly where I have we have just seen through these 2 crossings of
2 back bearing lines Then we used to take back bearing from third (po) point and if
third point also the back bearing line if also cuts at the same points where 2 lines
earlier have cut then we are very um very much sure that we are on this particular location
This concept of back bearing was on 2D This (con) concept with the satellite technology
especially with navigation systems it became a 3D technology so (he) here what basically
is happening that there is a constellation of satellites which we will see which system
is having where what type of constellation and then these satellites are at in each orbit
they are at say if I take the example of GPS then there are (si) 6 satellites are there
6 six orbit are there and in each orbit you are having 4 satellites and all these are
having they are having in each orbit they are having at equal distance each satellite
is having its unique id
So what each satellite is doing also they are having synchronized atomic clock so what
they are doing they are sending the signals which is a times stamped date stamped location
stamped signal and saying that I am in a space at this location and I am dispatching this
signal at this moment so when a receiver receives this signal I know that how much time it has
taken because there is a time which is when signal was sent from there it is there and
so the time taken by that signal to reach to the receiver gives me the distance if I
multiply by the speed of light and why is like in concept of back bearing if I start
getting signals by receiver from 3 such navigation satellites then I would know where exactly
on globe my receiver is
So it’s like in back bearing minimum back bearing readings were only 2 required but
it’s a 3D so minimum 3 are required to know X and Y position that is latitude and longitude
but if I want to know the height or elevation of a point where receiver is kept then I have
to need to have signal from 1 more satellite and that is the 4th and that will give you
the 3D so 3 satellites will give you 2D 4 satellites will give you 3D
We will see all these things in little detail as well then how GPS works the GPS devices
tells you where are you and while calculating the exact distance from 4 GPS satellites at
a given time the first one there are you know this thing these figures keep changing because
there are spare satellite but the in case of this US GPS American GPS or navigation
system which we call as GPS a minimum constellation is the 24 satellites in 6 orbital planes
6 orbital planes are there and so that at a time minimum if you are in a open area you
should be able to get at least signals from 6 to 8 satellites at a time minimum and this
then these satellites continuously transmit their precise location every second they are
sending a pulse a signal from there towards the earth that I am here at this moment I
am dispatching Let me give you analogy
Like if I post a letter from Roorkee to say Chennai so when I leave this letter into the
letter box then in the post office it is stamped that in it is being posted from Roorkee on
this data and this time When it reaches to Chennai then again that post office will stamp
so while looking these 2 posts 2 stamps I can estimate that how much time it has taken
to reach from Roorkee to Chennai Almost similar concept that the it is in digital form that
signal once it received the distance is calculated and direction is known so that this range
is basically these are the ranges
As you are seeing in this animation that as a person keeps moving that the he is getting
the location because the 4 satellites are continuously communicating with his GPS receiver
and that location is being calculated every second for that person or for that receiver
so the GPS receivers pick up the satellite signals which are being transmitted by all
these 24 satellites all the time every second and determine out location by a triangulation
method so this is how this what is that triangulation that working out our location based on intersecting
area between all the GPS satellites at the GPS receiver communication The GPS receiver
which are communicating with them
Now think that if I am on the mountain on a hilltop then I would be able to get may
be even signals from 10 satellites and if I am say on Mount Everest probably I might
be able to get signals from 12 satellites because then hindrances are less so if if
I want to have a good position then I I need to have a a very large open sky If I am in
a valley then I might be getting very less signals From less number of satellites signal
quality might be also good not good and therefore my position estimations might not be also
good
Nowadays when we use in our smart mobile the Google Map when we switch on initially it
will show a large blue circle and after some time you would realize that that blue circle
has become a small blue circle so what it is basically indicating that now that initially
the error margin was much larger that means the estimation was very poor but once it starts
getting the signals from various satellites GPS satellites then my position has improved
position estimations have improved and therefore the error circle which is blue has reduced
and the so that sometimes by using some other application programs you can know that what
kind of accuracy you are getting
So we will be we will we will go on further on this how GPS works basically as I have
been saying that this the this like in case of towers mobile towers how they get the concept
of a GPS how they get the signal that each tower if each tower keeps transmitting its
location as well apart from signals then wherever these 3 (sig) you know the range of these
towers that means these circles 3 circles will cut that is the position where I am standing
This is how a GPS works Think that instead of 2 dimension on plain area on a surface
of the earth if I consider these as spheres and instead of towers I consider them a satellites
in the same way when these spheres will cut that would be going to be my position of my
receiver so this triangulation location or triangulation concept is here it is in 2D
but in case of satellite it becomes a 3D So satellite 1 whenever this range is available
I know radius of my sphere
So one satellite will give me the one (sa) one is sphere another satellite once I get
start getting signal I find the distance between receiver in satellite then another sphere
will come Now then there will be 3 spheres Suppose I am getting signals minimum from
the 32 satellites so wherever these all 3 satellites will cut these spheres will cut
in circles it is looking only 1 points but in case of a spheres there will be 2 points
so 1 would be very far from surface of the earth therefore the other point which is close
to the surface of the earth is going to be location of the receiver so the 3 satellites
together provide the exact location of the receiver
And now as I mentioned that each satellite broadcasts radio signals with their location
status and precise time information This is very important to note that each satellite
every second is sending signals and these are in the radio frequencies and that means
that in all weather conditions day and night 24 hours we can receive signals from the constellation
of 1 navigation system for example here a GPS which is American one and once the time
is calculated the dispatch time receiving time then distance is (go) available
Now 1 is sphere for this satellite one is sphere for this one is sphere for this and
one is sphere for this and likewise GPS radio signals travels at a speed of this 300000
kilometer per hour and GPS receiver device receives radio signals noting their exact
time of arrival and uses this calculate the distance from each satellite Basically the
distance once distance becomes available then this imaginary sphere which we I am emphasizing
can be calculated or can be drawn by the receiver itself or calculations about or estimations
about positions can be done
So once a GC a GPS receiver and knows its distance from at least 4 satellites it uses
the geometry to determine this exact rotation of the earth in 3D If I am only interested
in 2D then um minimum 3 satellites are sufficient but if I am I want to know not only X and
Y but elevation as well then I need to have the signals at least from 4 satellites
As I have mentioned that when US was developing their (Nav) Navstar system that is the GPS
or Navstar satellites that is the GPS the (simil) same time the Russians were also developing
a system which is called Glonass Later on some regional systems have also come which
is the European countries have also developed Galileo BeiDou India has also developed I
will discuss little later but why there are requirements once a global navigation system
became available in somewhere 1990s earlier it was accuracy part was not as good as today
but at least it was there and it was globally available to anyone who is having appropriate
receiver so why other countries started developing
Because if we start depending everything on the GPS for all kinds of navigations whether
for aircraft operations or for taxi fleet operations or for the railway engines operations
then it it would it would have been a complete a monopoly of US and then whenever they wanted
they could have switched off and all navigation system would have gone completely haywire
So in order to you know not to depend completely on American navigation system that is GPS
Russians also developed Basically it was originally Navstar or GPS was developed to for the missile
technology but it it became much more popular equally in our day to day life
Then Glonass was again it is also a (navi) a Global Navigation System and even in nowadays
in not very expensive a smart mobiles their receivers are capable GPS receivers are capable
of receiving signals from Navstar that is US GS GPS as well as from Glonass so in instead
of getting from 1 navigation system signals from 1 navigation system it is possible to
receive signals from many navigation systems and so know these receivers small tiny receivers
are coming with smart mobiles or hand held GPS receivers that they can receive signals
from various navigation systems
So Russians also developed parallel to the system and almost same time the third system
as I mentioned by the European countries that is the Galileo but Galileo is not truly a
global system Galileo is a regional system Then Chinese also came because they too never
wanted to depend themselves on GPS that is Navstar or Glonass so they too came with their
own navigation system and design wise constellation wise it is completely different than typical
GPS system or Glonass system This BeiDou navigation system of China is having all together different
constellation
Same time also when India realized that we need to also develop our system (be) not only
for missile technology but also for day to day life in the civilian world for all kinds
of navigation so we went with this kind of initially it used to called IRNSS and then
later on it was renamed as Navic and say though it has not become fully operational but I
am sure that very soon our mobiles will have a receiver which might be receiving signals
not only from a GPS that is Navstar Galileo and BeiDou because BeiDou also provides it’s
a global navigation system it also provides data free of course and may be when if I am
using such receivers in India I might be also getting signals from Navic as well
If I get from even in a valley if I get signals from 10-15 satellites of different navigation
system definitely my position estimations are going to be very very accurate If I compare
just or if I get signals only from 1 navigation system so that is the advantage for us going
to be that if we start getting signals from many navigation systems of the worlds then
our position estimations are going to be very accurate Generally we get with the simple
these smart mobiles we get say position estimation there is a error margin may be 5 meter or
10 meter sometimes but if I am getting signal from 3 4 5 navigation systems that accuracy
might be improved within 1 meter which is very good for many applications
Now this whole I have so far introduced a very briefly what is GIS also very briefly
about the GPS and remote sensing we have been anyway discussing so now this main purpose
of this lecture was to have this how to integrate all these technologies so that we get a very
nice product So there are different models which we can think that is one is the interactive
model of integration which is very popular very commonly used As I have said all the
data which is either remote sensing data or data from coming from GPS or your GIS platform
they all handle the geographic data that is means special data and the that is the advantage
So the the coordinates basically or the you know like if you are having a satellite image
after doing georeferencing or rectifications image rectification you get the coordinates
for the image and satellite image so that becomes your georeferenced satellite image
and this this is 2 way because sometimes standard a georeferenced image can also be used to
georeference another image which is not yet in geographic domain it might be in geometric
domain or may not be yet georeferenced to that is why it is 2 way Nowadays for like
for let me give you analogy like nowadays for very high resolution images if we want
to do a georeferencing that means we want to convert from geographic coordinate to (geomet)
from geometric coordinate to geographic coordinate then we are also using the (coord) coordinates
in the for GCPs our ground control points using even Google Earth
So a registered or georeferenced a satellite image can also become a master image for another
image which is not yet georeferenced so that is why is it in 2 direction Same day once
I have got the georeferenced data satellite images then I get the database construction
on a GIS platform which will provide not only the satellite data information the output
from the satellite data information and data images but also data from other like digital
elevation models may be a soil map may be a land use map may be a forest cover map and
so and so forth because GIS is capable of handling all kinds of information especially
the spatial information on a digital platform
And then I might perform some kind of modeling on a GIS platform that can go again back to
my satellite images to see like people are doing nowadays that whatever the product they
are creating on a GIS platform after doing all kinds of analysis on satellite images
and along with other datasets they put directly on Google Earth and then see that how it fits
there with the surrounding so (the) that is why this is another arrow is there That once
I have done the modeling I can put again on the Google Earth and see things along with
the surrounding as well as I can transmit to some others who can also see once they
double click on the Google Earth so that’s the advantage so it’s a interactive model
of data integration and this concept is given here
Then there is a another model we can think of which is a hierarchical model of data integration
that we are having coordinates coordinates might be coming from survey toposheets coordinates
might be coming from GPS or coordinates might come from standard products from Google Earth
Google so they they go here for my data georeferencing of satellite images and again for overlaying
with the other maps on a GIS platform I might be having a GIS database separately which
is again georeference having geographic coordinates and then I can integrate again do the modeling
and can create some products
Modeling here means suppose I am working you know for landslide hazard zonation so for
that purpose I need lot of information not only about the slope but the land use and
the road network maybe some you know geological structures faults and other things so all
these things once I am available I may assign certain weights or I may employ some known
models for that particular area and can create a map an output a model which will show that
where if these conditions remain like this then where the slope will fail first and which
are the slopes which are most vulnerable and the next and next so that is basically modeling
predicting about the future
The third type of integration model is the complex model so (ra) rather than having interacting
or hierarchical model a complex model of integration can also be thought here That again the coordinates
the special information becomes the key so coordinates are there overlays are there on
a GIS platform and then you may have to have a database construction instituted our collection
that means going in the field collecting the data collecting the samples analyzing the
sample putting into the database coming into GIS and then again creating such models environmental
model or any other model like may be soil erosion model or some other models may be
putting on a GIS a satellite images
Today I am (us) suppose I have used the satellite images of 2010 now I have (us) I have also
seen in 2015 now what would happen after 5 years I may project I may model and then when
2020 comes I will be able to see that how accurate model was because the satellite images
can provide the time series data so all these things are possible to do it even if you one
goes for complex model of data integration so all kinds of models are being implemented
to integrate data specially on GIS platform data coming from satellite images data coming
from GPS data coming from variety of sources that is the spatial data and field data survey
data and all these are going on a GIS platform and then you create a final product a model
a predication and other (prod) as per user defined
So what are the what is the possibilities of the future future integration possibilities
with RSGIS and GPS just as a as a thought things may work little differently because
we may have more powerful more useful images more powerful GIS technology more better GPS
signals or navigation signals may be some technology might be coming but if we think
that whatever the (possi) whatever the technologies which are present then how these things will
be integrated that what we are going to see an increased number of remote sensing platforms
that is more number of remote sensing satellites leading for more accurate and regular data
Higher spatial resolution data higher radiometric (spa) resolution data higher temporal resolution
data and on regular basis that is one very real possibility Then the current era that
is times to come and most likely continues to emphasize visualization of information
because I said you remember in other previous lectures I have mentioned that a picture tells
10000 a picture tells 1000 words whereas a map or model can especially a map can tell
10000 words So this visualization a satellite image will give you more information than
a simple picture and if it’s a GIS product then it may give you much more information
even in the simple satellite image so that kind of emphasis on visualization will continue
Remote sensing images will be the key input for all kinds of analysis and of course GIS
is going to be powerful and more user friendly so that person who doesn’t have much knowledge
of a a computer computer science programming can also use GIS very easily so more this
is what the future Navigation data coming from variety of systems 5 4 or 5 systems I
have discussed 1 more from Japanese side are also available so all these might get in only
1 receiver so it means 1 in near future we might be having a receiver which is kind which
is going to be kind of a kind of a universal receiver
So it can receive signals from all type of navigation systems whichever are presently
or in future such a open system might come a universal system might come and our accuracy
estimations will improve say to just few centimeters as nowadays we are it is possible only through
differential GPS but not with simple GPS navigation system so that is the geo spatial accuracy
definitely is improving it is going to improve very soon on this front And the last one here
is that user interfaces is to continue become much more standardized and user friendly so
all these technologies are going to become user friendly in near future so this brings
to end of this special topic of discussion Thank you very much