QGIS 2.10 - Buffer, Difference, Clip

okay this is Lex Berman with seven of the cutest 2.10 tutorials and i'm going to work on buffers difference and clipping and let's try a problem where i take a data set of Railways and I try to take a data set of power plants and I try to find out all the areas that are within ten kilometers from a power plant and less than five kilometers from a railway let me just give you an idea of how that's going to work all right so we'll zoom in to our area of interest which is Taiwan first we're going to add the power plants which is in a different folder right here so here's the power plants and here's the railways add both of those okay so there they are we can't really see the railways we better change the symbol on those a little bit make them thicker okay we can see stuff now so we have some railways and we have some power plants and what we want to know is first off what's within 10 kilometers from a power plant and what's less than five kilometers from a railway so to do this stuff we're going to have to have our units are our layers in projected space and meters for it to make sense with geoprocessing to work so the first thing we should check is just simply if our data is in a projected coordinate system which it is xi'an 1980 and the railways are in jiya 1980 okay they're both in the gauss krueger projected space and units of meters so that's a good start so the first thing we'll do is we'll buffer those power plants go in here to vector and we will do our geoprocessing buffers and the input layer is our plants that's a karma dataset which is a global power plant data set our units are meters so we'll just say 10000 meters and we'll output it to the desktop and we'll call it power 10 kilometers so basically they're 10 kilometer buffers around the power plants so that's we can see that it's quite a lot of area that's got a lot of population that had is within 10 kilometers of a power plant the second second kind of calculation we want was the buffer of the railways basically you can do the same way using vector geoprocessing buffer and from the railways we wanted a distance of say 5 kilometers that's going to be 5,000 meters and we can add those hope I didn't choose a name for it so I'm going to call that rail 5 kilometers so now I have kind of a combination of these just make those little transparent that's all so I have a combination of these power plants and the railways and I basically wanted to know where both the area is within five kilometers of a railway and ten kilometers of the station so if if it's more than ten kilometers of a station it shouldn't be in there and if it's more than five kilometers from a railway shouldn't be in there so it should just basically show me these these sections so to do that I'm going to do a vector analysis difference and we can go in there to our analysis tools and try to find it see maybe it's under geometry or is it difference it's under geoprocessing actually so it's a vector geoprocessing tool difference and I basically want to know that the railways are different from oh actually no it's not the railways it's a railway buffer and the powerplant buffer okay and I'll put that into an output shapefile which is going to be the difference file the difference of the rail and the power essentially close this actually this is what I wanted to see because basically what I wanted to know is for example you know where would you feel safe about building a certain thing a hospital or housing that's more than ten kilometers from our plant and yet within five kilometers of hoverrail so maybe that's a good place to put housing for example now one thing to consider before we're done is that there's a kind of an anomaly that's introduced by this which is that the the clip regions are buffers around the railways and they could extend like beyond the edge of the coast so we should probably clip clip those with the edge of our Taiwan coastline which is more accurate than this country file so I want to clip the buffers this difference real power with the edge of the Taiwan Shen Coast Xian code sorry so here's the different rail power I want to clip it with the coastline and this will be my bumper click ok close so now what I have is a kind of interesting result which is make that transparent so you can see it a little bit better so basically if you take a look at this where's my original Taiwan karma points can we see them make them a little bit more visible so basically we have areas now that are identified which are within five kilometers of the rail but they're more than 10 kilometers from a power plant maybe that's the kind of place where you'd want to build housing it's farther away from a power plant and yet still accessible to the rail and it's not in the sea because we clipped it to the edge of the map so there you go it's a way of using buffers difference in clipping to run summit now this

Channel: Lex Berman

Views: 30,040

Rating: 4.9545455 out of 5

Keywords: QGIS (Software)

Id: b3c_XRY7oQs

Length: 8min 43sec (523 seconds)

Published: Fri Nov 06 2015