 I spoke to you about the basics of GIS, what about the concept of spatial data, we saw two different data models and then I gave you the basic operations which are available under the raster data structure. Now let us try to look at some of the algorithms or functionality they are available under the vector data structure. So in vector what we saw we can have layers and the way the data gets stored in a vector data model is in terms of point, line, area etc. So when you want to work out any analysis in vector using multiple layer the one of the simplest available query for vector data is it is very strong in the attribute database because you know any point or line everything automatically a database gets created where you can add the attributes. So simplest as far as the vector is concerned non-spatial query and the thing is non-spatial query is one of the easiest analysis methods and maximum used in the GIS. See if you have come across the different GIS packages people might have used people who are working in GIS for maybe you know for about a decade. Map info had been a very powerful package similarly from yesterday they came out a tool called ARC view. The success for them and all they basically did query through database because many planners many you know decision makers they may not do any high-end analysis they would like to see the spatial data in the context of non-spatial data. So non-spatial data query becomes the easiest where you know you try to use the attribute table query like you know show me the villages which have no school or show me the villages which have you know school going children more than 500 and no school. If your tables are properly organized for the features then non-spatial query runs in a easy way and always non-spatial query means a single layer with attributes because you know of course when you have a very powerful analysis in the vector it will run spatial objects with non-spatial query here what I am showing is just the non-spatial query in a single layer like you know you suppose you have the data for anyone of the tables with block boundary you just say show the distribution of villages which have infrastructure facilities like which have post offices which have no facility which has post offices with bus stop banks like that if you put a query system can immediately generate the thematic map and give to the user here you do not need any high-end analysis or modeling or anything with simple query on the tabular database the map can be generated why the map gets generated the reason is there is already a link between the ID of the spatial objects with the record in the tabular data if you have touched that ID your results will go wrong so you know the link between your point objects on the current record must be correct then only if I select for a data for Mumbai it should show me the Mumbai polygon or not you know Pune polygon the link should not be broken that one has to keep in mind if the links are proper the system will generate it that is a simple non-spatial data query now coming to the spatial query broadly you can categorize as far as the vector analysis is concerned something which can run on two layers something which can some queries which can run on single layer okay in two layers I am not going to cover you entire detail of each and every functionality just to summarize same like what we saw in raster we saw overlay we saw conditional table we saw map algebra same way here you have the functions like union, intersect, identity, XR, clip, update, erase, split these are some of the common functionality available in any GIS tool which is a vector based tool so union means it is the same what we see in the set theory of union A union B means what? it will create a new set which allow all the elements of A and all the elements of B same concept is done here so when you say union it is A union B set theory you take back, intersect A intersection B which are common to both in fact if you talk in a Boolean concept A union B is Boolean R A intersect B is Boolean AND so both must be true and A union B is either of them can be true so Boolean R is equal to union and Boolean AND is equal to to intersect so suppose you look at it so when see operations are performed between two layers to get the relationship between them again the emphasis same like raster when I said in raster whenever you run an analysis please see that all your layers are of the same size you do a preprocessing and bring the data set so that every layer should have the same rows and columns, same projection, same resolution same thing is here never as long as these layers share a common coordinate system they can be related to so one should see that it is done so that one layer sits exactly over the other layer ok whenever a new layer is formed again the concept is same like a overlay in raster it combines the layers creates a table for whatever the combination occurs so whenever you take an overlay one is point can overlay with polygon line can overlay with polygon polygon layer can overlay with polygon so when do we run point with polygon suppose I take Indyaka data somebody gives me all the locations of hospitals of India and you have administrative boundary map separately you have taken from somebody showing all the Thaisil boundaries for every state you can combine both of them with point in polygon you will result what? you will result in a point layer see you have a point layer you have a polygon layer this contains the locations of hospitals this gives you the administrative boundaries let us say at the block or Thaisil level when you run point in polygon you will result in a point layer but it will have one more attribute showing in which polygon in which village I am sitting or in which Thaisil I am sitting so that is the advantage of point with polygon same way you can do line with polygon you have the road network map you put it with your state boundaries let us say all the national highways network you combine it with the polygon layers of states immediately you will result in a line layer only a road layer only but the road layer will break wherever it meets the state boundary and the roads will create a table showing I am in the state it will have one more attribute whether that part is in Maharashtra or Karnataka or Gujarat that is the advantage of line with polygon and when you run with polygon with polygon we use the word union polygon with polygon it is same like a set union so you result in a new map which contains the polygon boundaries of both the layers and the new table gets created suppose a Thaisil one corner gets intersected with the part of a slope one you will have a new polygon and it will have a new ID which gets concatenated from Thaisil one and slope so the table will guide you along with the map how to proceed union is a very common operation whenever you have to combine more layers so union is very commonly used as I said it is a Boolean R operation and contrast to it when you want to run this is an example which you can see I said you know when you have a polygon layer another polygon layer system will overlay it system will create you the table it will do everything and give you the result but you know the complexity what the system works one should know this is an example which I got from you know one of the public domain tools where they have taken only two polygons one polygon is in one layer another polygon is in another layer they have overlaid you see A is a polygon B is a polygon when it is combined you see how many new polygons are formed if you look at this diagram you will see there are nine polygons one which contains both A and B four which contain only A and without B so whenever you try to run a union operation the complexity increases but since they also create a default table guiding you it becomes easy so many polygons are there as per your criteria what are the area everything area perimeter everything gets stored automatically the system can use it ok so this is union which is an example of again a union operation where you have one map another map when you combine it you get an overlaid map and the corresponding table also gets created now we saw Boolean R now comes Boolean and which is an intersect so intersect when can we use because you know when both are common you have to use it you have a soil map you have a slope map you are interested in the polygons which have a specific soil category and a specific slope category so it looks those polygons picks up and creates a new layer ok so intersect is contrast to A union B the area which are common to both gets intersected and stored of course intersect can be run in many ways see you can again you know you have a point layer I say I have the locations of hospitals for the entire country you want only to pick up for your state so put that polygon alone it will crop it out and give you a layer giving those point positions only for that polygon so I want I am interested in hospitals only in Maharashtra state I just intersect with that polygon it will pick out and give whether it is a roll layer or point layer or polygon layer based on the intersecting layer it will crop out and take it ok and another is a clip operation of course symmetric difference is there I said update is there are number of operations only few of them I am just showing clipping is something you want to clip out only what you want it you have take a map land use map of the entire country you want to clip out only for your study area you can simply put it you can clip out and take it ok so it is like windowing what we do in image processing same way one can just clip out the area that is also possible and you know some area you want to mask you have the total map due to security reason or something you want to mask the data simply put that polygon and run the mask operation in your thematic map the data will be masked so mask is again a useful operation in vector and then update so updation is our regular thing as I said you know unless information is up to date nobody will use it so if you have a old land use map or old road network you want to add the new road layers in it take the new road layers alone ask the old map to update it it will add all the new segments to it and give you an updated layer so input can be a point layer or a line layer or a polygon layer accordingly you can create an updated layer and another is split these are all what I am covering is what two layers operation in vector GIS ok so split is something again an example of I will take our country you have the entire road network of this country you have taken from some department and you want for every stage separate that way you have to do maybe you know for 27 times you have to clip it out put this boundary clip it this boundary clip it split is a command where if you have the road network and I have all the state boundaries I run a clip operation for every state it will split it and save as many layers so you know instead of doing one click multi clip operation is done and how many input polygons are there in your second layer that many layers get created automatically so you know somebody was asking why you know how do they store the region data how do they store you know multiply data and all all these functions although they started generating when an application demanded see any technology gets evolved or grown so you know basic commands they would have put maybe you need an intersect and somebody says ok I want to run this application when the developer thinks ok this is a functionality which is not available in the tool you have to add it that is the way you know more and more functionality had been added both in the raster domain as well as in the vector domain split is also a very useful tool when we try to work for the multi polygon area so these are some of the double layers operations now coming to single layer we saw there like you know what we saw buffering I told you about proximity I told you about the distance the functions which are available in vector domain they have developed those operations based on what is happening in a two layer operation see whenever you try to take a two layer operation I have one with three four polygons another with three four polygons I combined I may have n number of polygons and what happens there may be small small polygons which may not contribute anything for you it may be due to even poor digitization it may happen so they have given commands which helps you to merge the nearby polygons and dissolve the boundary ok see it operates on a single layer merges the selected polygons with neighboring polygons that have the largest shard border between them and that have the largest area so whenever you try to run a union operation normally they say it creates unwanted polygons which we call a sliver thin skinny long polygons get created which we term it as sliver polygons these sliver polygons can be removed by using the eliminate operation normally they ask you a threshold value that they say how much area the polygons should come which can be eliminated you give that threshold value any polygon which has the area less than your threshold value they get eliminated ok so eliminate is a common and another thing is dissolve dissolve is like eliminate but what it does it doesn't eliminate it suppose when you overlay you come across two polygons the new id generated let us say soil one slope one is same for this polygon and the nearby polygon let us say two adjacent polygons are with the same id then why should you have two polygons common boundary can be removed so dissolve is something based on if the two polygons have the same user id common area gets erased and it becomes a single polygon ok and of course buffer same like what we saw in vector whether you have a road layer or a point layer or a polygon layer buffering is one of the useful commands as far as the spatial planning is concerned very commonly used so whenever you have a layer you can give the buffering distance so that the buffering can be immediately created and the buffering can be like you know suppose you have a road you want only one side buffer other side may be the city you want to protect only other side system can create both sides buffer only one side buffer when you have a polygon like a city you can create only an internal buffer you can create an external buffer both the buffers giving a selected distance buffers can be created so all these options are normally available in a vector so raster gives a lot of functionality vector supports a lot of functionality this is an example where you know on a land use a raster buffer is drawn along the water body to see what kind of land use is covered by those buffering near the water body ok so we saw some of the vector operations some of the raster operations and one more analysis which comes in the GIS network analysis network analysis runs on a vector model and the usefulness is for transportation so whether you want to find the shortest path whether you want to find an optimal path this can be used ok we give a source and destination you have a network connectivity properly that network should be formed if there is a gap you will have a break if the network is properly connected then one can run it for shortest path specially for routing and also for location allocation analysis you have all the demand nodes you have the supply nodes like you know you are a factory where you have a go downs warehouses are there you have to pick up and distribute the commodity or you are doing a distribution like a fair price stop distribution these things can be done when you have a source and node properly it can be distributed so the thing is for giving the demand node and supply node how the vehicle should go that network it decides optimally so location allocation is one of the applications which can be done in network of course there are more applications are not given you the view graphs like service area given a location like I say a bank or a hospital or a school you say it covers an area around one kilometer it can provide the service around one kilometer around it so what area it can cover it can show will it be a circle when I say this location will cover one kilometer around it it won't be a circle because as I said in network we don't work on crow fly distance we don't work on Euclidean distance we work on individual road network so every direction it will take the road network which covers around one kilometer distance it will link it and create you and irregular polygon it will not be spear it is not radial so service area also it's in fact service area is a simple application which is widely used in a GIS and a network technically simple there is no shortest path finding nothing it only calculates the distance it connects but very useful as far as the user is concerned so that is as far as the analysis is concerned then comes the visualization of the data GIS gives you enormous facilities to visualize any software tool whether you want as a map whether you want as a table whether you want to look at only as a database you want to only temporarily use as a query all facilities are available people can pan the image visualize and say fly through is possible one can you know change the scale projection the way you want to do it so you know a lot of options are available as far as the visualization is concerned these are some of the examples which I am showing from gram plus plus it is a map where a simple map is shown with the house network in one of the slums in Bhopal and you know facilities are normally provided for zooming it can even any path moment you are visualizing system helps you to zoom it you can have a 3D visualization where the terrain can be put virtually over the topography and one can visualize it and another thing is it can help you in hierarchical map you suppose you have the area for the entire state you have the data for in the state you have for every district and in the district you have for every Thaisil in the Thaisil you have for every village you can open click click click if they are properly linked at any hierarchical level you can open it query it get the result so hierarchical viewing also is possible in a GIS and before closing I want to tell see one main issue as far as GIS is a very powerful tool it can do many things applications are very many but what we all should keep in mind is accuracy if you are wrong results will go wrong don't think it is a God it will do it will do nothing if we are wrong if our data is corrupted if our data is poor quality you will not get proper result that people who were doing for whatever the application accuracy is very very important a lot of research is going on globally only on GIS accuracy uncertainty etc data quality because you know if I approach raster model I will get one result if I get a vector model I will get another result if my grid size changes I may get another result see everything changes because you know it is sensitive if I change a weight you do some multi layer analysis let's say crop suitability you may give one set of weights I may give another set of weights your location for reservoir will be different my location accuracy is very very important right from the sources data sources who are done it what has been the method he had used what satellite data he had used to prepare that map one has to know see today lot of spoken in GIS community about metadata data about data so the data sources you should know what way they have analyzed the data you have to know when you depend on secondary sources if you are doing your primary survey if you add the information in your data I bought this data on such and such a data and such and such a method I used to prepare that map so that for another user it will be useful so always information should be well done and a lot of research is going on conference proceedings are there books are available on errors in GIS so entire our results will depend on what we have input so you know your position I used to joke in my class I said if I say I will find a location for school instead of in Mumbai city I may be sitting in Arabian sea because my data is bad you are not wrong in your analysis or in your GIS tool so you know one has to be very careful and when the application you take please see whether your scale suits your application what I do for a city what I do for a district what I do for a campus they are all different the scale should be good whether you have all data relevant for your application did you get or there are information gaps based on all your results will have GIS can do wonders provided we take care of all these things and so if you have all the concepts what we call spatial modeling is it is the process of manipulating analyzing spatial data generate useful information for solving complex problems general definition on spatial modeling how do you do whenever you take it identify problem break down the problem simply you have to put it put it put it in such a level you should come to the atomic level what you want to do you have the data what method you are going to use will your GIS support it you have to draw draw break it and bring it a full flow chart then only unless you develop clear and logical flow you cannot do the successfully they use the tool if you do everything run the model modify if it is necessary you will get the results so and as to keep in mind applications are many many there is no area where GIS cannot be used maybe you know you may think that I am working on GIS I am trying to promote that is not the case every day we come across new applications in GIS and just listing a few of them and as per last year survey it is not even 2007 survey 2006 newsletter when I got they said annually it is a 12 billion dollar industry in terms of what data there are people who provide data on charge because as I said information is power it can be bought and sold for money so data software services people provide services data conversion services web services etc publications training so it's around the 12 billion dollar industry every day the technology is growing applications are growing and if you want to classify overall the GIS you can have a height because you know someone asked me after my first lecture how do you compare our GIS with other tools see everything has a goal objective the way it can work there are tools which are available for crores of rupees there are tools available which are for thousands of rupees so what we look what we can afford what application I am going to do accordingly one has to spend money great government department can pour crores of rupees a small college may not be able to do that so you know we have to look at all these things there are enterprise GIS available there are desktop GIS tools available just you know you can have a palm top or a PDA GIS runs today there are GIS I told you when I spoke about components that you know modeling libraries are available components are available in GIS you buy the components you customize your full application with your own programming so that the components will sit like a back and you the whole SDSS will look like your own tool components are available simple viewers are available like mapping for RQ where you don't need a high end things and then web based GIS web based GIS somebody spends money to load the server and keep the GIS and keep the data we people as a user go to the browser query it and get the result we don't spend any pie somebody maintains he has to spend he has to spend for server get the data GIS map server everything he had to spend we as a user simply we sit in our lab and we try to query it and get the result ok so software at all can be classified in different categories to conclude I tell if you have a clear objectives proper orientation time scale what you want to communicate to the user as a result things are all there the management of GIS will meet the success so understanding GIS requires science systems and studies we know that you know GIS provides a framework to manage today's world the real value of GIS is in its problem solving capability it's growing its future is also growing specially in our country there are a lot of you know untapped applications the requirements etc is that very high in GIS if you learn properly put properly promote properly it can meet success ok thank you yes will it be possible to have some direction in between and check or suggest that some alternative can be adopted absolutely absolutely possible 100% possible you can put the road where there is a construction work going on where you have a traffic jam where you have a hindrance all these things you can give us an impedance value so that system will show you the alternative ok that is why I say it is not a shortest path it is an optimal path ok network gives a lot of capabilities and even when one network it has done if you say you give me a second alternative system can give that is possible missing data is there means see suppose I will tell you if you are using an interpolation you can get the missing data that is one of the methods you can use trend analysis to get missing data but you know the results will not be better than what you have input see I have a 450 contour and 470 contour in between you will assume it is linearly growing in between Darisa valley system will not know follow but analysis should be done separately see that is one thing another when we say on error evaluation I normally try to talk because I am not covering a lecture on error or here see normally sensitivity analysis is a must today in GIS any paper you see they will write sensitivity analysis because see I put a weight to meet as my expertise that looks correct if I go and sit to next colleague he may say this weight is wrong I will put another weight your result changes so what they do whenever you try to do a multi layer method with putting any criteria you get a boundary a range of min max weight and if I give minimum what is your output when you give maximum what is your output so that your result can be within a range not point location so that is way they do so missing data can be done only as of today by interpolation and using trend analysis etc. if major parameter is missing you have to change your flow because nothing can gap it see I saw some student or you know some department person who came he wanted to work on water resources he brought a big area rainfall station so he says rainfall is very important for full rainfall I said then that layer is not going to play a role because you have only one station so you assume you know everywhere rainfall what is that it is going to do so you don't need to use that layer at all no doubt rainfall is important but with single value you cannot do anything so this we have to think and take care of whenever we do the analysis ok