IIRS ISRO Digital Learning Programme · Transcript · · Updated
GIS Data Models (Spatial and Non spatial) by Mr. Ashutosh Kumar Jha – Transcript
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Summary
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- GIS data models use raster and vector data formats to represent complex real-world features like roads and continuous aerial phenomena.
- Vector data models rely on geometric objects like points, lines, and polygons, along with topological relationships such as adjacency and containment.
- Raster data models store single attribute values on fixed grid cells and compute coordinates on the fly using origin coordinates and grid distances.
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Transcript
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So, good afternoon. Today we'll be having a discussion on GIS data models. So, in this lectures basic objective is to find out or the learning objective is to understand the importance of data structure in GIS analysis.
Then we'll also look into how does the special relationship are basically presented. So, there are different special relationship, how it is presented, that's what we'll discuss. Then we'll also see the basic data structure which is being used in GIS, mostly the we'll be restricting our discussions to just 2D data structures.
Then the most models which is being used to represent the data GIS data is raster and vector data sets. So, we'll be seeing how the data sets actually get represented in raster and vector format and basically their uses, few of the area uses and uh uh different formats, how it is being used, that also we'll see.
And then we'll also explore few of the open standards which is being used for representing this different special data models. So, we we'll be concluding with a set of examples of GIS data format which is currently in is being used. So, we'll look into all these till the in at the end of this whole sessions,
you should be able to explain what exactly why do we need a GIS data structures. Then you should be also able to understand what's the difference between raster and vector data types. And then we'll see uh basically the special relationships and their topological relationship, how it is getting represented. So, what exactly is the meaning of the topological relationship, that also we'll explore.
And then we'll see the few of the side effects if you go from vector to raster data formats. So, what are the effects and in those cases uh what needs to be taken care of and the corresponding quality assessments, things also will just uh briefly discuss.
Then we'll see a few of the examples uh which uh you should be able to explain and see that if somebody talks about a shapefile or maybe a GeoPackage file formats, you should be able to understand what exactly is the underlying data models in uh in which these data sets are stored.
So, we'll see the Open Geospatial Data Instruct- uh Consortium base, that is the OGC format data based uh and different data models. So, let's take a basic overview of what exactly is the GIS.
So, in GIS, generally there will be a few user requirements. So, as you can see in this, this user requirement is just to find a distances or the path between place A to place B.
So, we'll try to find out what exactly is the dis- uh the different path which is available if you want to go from place A to place B. So, if you want to solve these problems, uh as we can see that the uh the features which is present on the earth and which is being represented as a satellite imagery is quite complex.
So, there are trees, there are houses, there are uh roads, there are uh buildings uh and a lot of other uh in- structures uh special structures which is present on the ground.
So, what we do is we extract only the important informations which is present in reality in form of certain data models. So, that the uh different type of GIS analysis can be carried out. So, that's in this case uh we need to just extract the different road networks and the places where these road networks are interconnecting those
nodes and the path needs to be found out. So, that we should be able to answer query that which is being given to find out a path from A to B.
Similar kind of problems we can have in larger domain as well. So, like we can be there may be a problems or related to ecological analysis, cultural analysis, there may be in a hazard base analysis and as well as different network and connections as well.
So, in this case we are observing that we need to find out multiple solutions from the same real world by extracting the certain informations.
So, for that we have to do some kind of organizations of the data so that the user requirements or specifications can be mapped to specific use case may be related to a finding out path, maybe some ecological problems and so on.
So, for that we have to look for somehow to organize that data sets. So, those data sets may be in form of databases or in form of files and so on. Then what we do is we execute these models or these there are different processing models according to the problems in a specific environment using certain functionalities. For example, let's say if in the in the examples which we just
discussed that we need to find out the path from A to B. So, to find the path there has to be a certain algorithms which needs to be executed and that's what we do as a part of GIS analysis where these data sets whatever data which we have taken that will the organized data sets goes as an input and then finally we get an output in form of the shortest path. So it gives you a
kind of a subset of a set of edges or nodes. If you put it them if you put them in a sequence then you'll be able to create a path. So that actually is a part of functionality which takes those data as an input.
And then finally in GIS uses what we do is we give or we whatever output is getting generated through certain functional capabilities. What we do is we do and represent it back to the user. So the output may be in form of map visualizations and so on.
Or it may be in form of instructions. So you may be aware of the certain instructions which you get it in your map services through Google Map and so on. So there will be one person keep which may be involved and giving you continuous uh uh basically the instructions.
So as a part of GIS if we if you see the overall workflow requires that you need to have certain uses or a kind of a specific requirements that has to be mapped into a certain mathematical and conceptual models and then finally we do certain amounts of evaluations.
So for using these models and usage uh which which may be an iterative as a part of the iterative process the first step required is a kind of data organizations. So if you if you just zoom in to the first problem again so from that perspective if I if you take it the basic GIS requirement is finding a shortest path.
So as and that's what as a human being will be interested in so you don't bother about what exactly goes in your Google Maps so you simply uh type in uh, the two and from two places.
And finally, you get an output that gets generated in form of maps. So, uh, the GIS basically gives you the, uh, whatever the requirements are there, the user requirement that gets converted into a very GIS specific questions. That is finding a shortest path. So, that may be the, uh, GIS questions, which may be further elaborated in term of specific algorithms and so on. That can get executed as a part of GIS process and
models. And finally, you get the solutions as a part of answers. So, so to do this, the data organization is the basic fundamental part. And that's what we will be discussing and trying to understand how exactly the in the machine the data which is there in in a very complex, uh, reality form, how it is being organized.
So, let's take a, uh, questions or the informations which is presents to find this, uh, path from place A to place B. So, this this is just a simple query which, uh, as an, uh, requirement is to find, uh, distance from a place A, that is, uh, the Indian Institute of Remote Sensing.
And there is one of the important place of, uh, Dehradun, which is called a Clock Tower. So, these two are the places in which we have to find it out the path. So, to find out this path, uh, if even if you don't have any machines or you are not, uh, using any GIS solutions, if you want to find out this particular path, then you need to ask a few questions to, or maybe you can ask
someone who will guide you that how can you, uh, reach Clock Tower from a IRS. So, in during their, uh, uh, explanations, they will use a certain, uh, names. Like in this case, there's a Kalidas Road, and they will tell they will understand that Indian Institute of Remote Sensing is located at Kalidas Road, which is connected to, uh, uh, Rajpur Road through New Cantt Road and
then we can get a uh connectivity from IRS to uh Rajpur Road. That's that information is available. So, these informations, whatever informations we have, if you try to put these whole informations uh to your machines, then we have to do a certain organization. So, generally whenever we say a data organizations, as a part of your uh uh to