QGIS Visibility Analysis

in order to do these ability analysis you have to install an experimental plugin you can also do it through gross but that requires you to work within the grass GIS so this is actually not part of the course that you are doing right now although that you are more than welcome to explore grass it has lots of capabilities and makes things very easy once you get the hang of that new software especially because it links directly into cue just so it's very useful for a lot of this you have been using saga saga is very powerful for geo statistical analysis for example you can see all the kind of tools that you have you can create morphology cover to slope anything like that for example the basic analysis tool for terrain does channel density calculates catchment areas for you slope aspect curvature anything like that so it's very powerful but it doesn't actually have a usable vision visibility analysis to that you will have to install an experimental plugin so your the plugins manage and install plugins go to your settings you'll normally land there so go to your settings and say you also want to show the experiments or plugins then you go back to your plugin view and you just simply so you'll look something like that you just look for visibility analysis they at the bottom you'll have to install it it will work for any qgs from about 2.8 to 3 as well I have it already installed but I can reinstall it for you simply install it it will then appear in your processing toolbox under visibility analysis at the bottom if you can't find it you can just simply search for visibility and it will come up it's a fairly straightforward plugin to use but what you have to do is you have to create your viewpoints first so you can't actually use your existing towers so what you'll have to do is you use your points as you saw all your towers though however you have called them you would have them as telecom towers underscore projection be sure it's a projected layer that your inputs you observe locations and then you will have to specify the digital elevation model that you're using you must use a digital elevation model that is projected if it is in the datum so if it's not planar it won't work you have to use a planar projection in this case I'm using an ID w rest the surface elevation surface that is projected into my L o 27 so hard to be hook and then projected into my latitude or my prime meridian of 27 then you must use the primary key of the input layer as your observer IDs you give it a radius of analysis how far it is now I have looked at the extent of my raster and it extends for about a hundred kilometers in each way so that's then equivalent in meters there so if you want to do that easier so that's 100 meters that's one kilometer that 10 kilometers and that's a hundred kilometers so this is the analysis radius it's going to use observer height is basically how we see it refers to us as people the height that we can normally view things one point six is a little bit too low for me in this instance it should be one point eight but for the average person this will be one point six and the target height will be the observer height so by Telecom communication towers will normally have a height of about 15 to 20 meters so let's just put in 15 meters they have anything else empty and then you writes to file you don't have to write to file but it's advisable that you do so we call this observer points if you don't write the file becomes a scratch layer and you actually lose it it's a temporary layer this will then create your observer points and here they are so they are exactly overlying with the existing points the towers which were there before it just now creates the correct input points for this visibility analysis that you need for this tool then what you can do is something called an interval ability Network looking at which towers actually visible from which other tower so here we've got my output layer the remove just make sure you use the right one so you open the tool the output layer two output layers I'm going from one to the other again you must use the digital elevation model that is in a planar projection you can take a cut of curvature into account for example and then you just run it again save two files over space this would be my answer visibility Network and you run it and there's my interval ability Network you can see some of these towers are actually completely isolated in the view if you switch on your surface you can see that there are in fact behind ridges so you won't necessarily have a visibility between them so this is the interval ability Network shows you which point is visible from another but actually interested in is the view so the view should works out which point of the raster is visible from the input observer points so you'll have to again select your observer points your output layer that you created using the tools and that planar projects it's de M the ID W in this case you do want to take account into account with curvature and in this case you actually wanted to save to file so I'll call is my vis raster and I'll run it finish running it will look similar to the one that you ran in arc you can see that it is shown in values so all the black values the zeros are not philip visible and the numbers from 1 to 37 are areas that are visible for the highest visibility being the ones that have the highest value so 37 in this case to make it easier for you to actually see those just change the just change the visibility of it how you going to draw it because then you're actually able to see the the numbers better so in this case I just want to use a multiband color one for example or unique values probably the best if you use random colors and then you just simply add the one that's not visible you call it's not visible everything else is visible at various in various method source various ranges so you actually leave those out because there's some visibility from one telecom tower for example but zero is where you have areas that aren't visible so if you show those you'll be able to see it a little bit better so if I remove my visit my a DW from underneath you can see all those red areas those are the areas that are not visible from any points any tower within the region assuming that a tower is 50 meters high and then it goes to about 1.6 at human eye level so this is how you would run the V set using the plug-in what you would do then in the practical is you would create a new tower that places within this red area here at just north of Munakata so I would go to my new tower I would make sure that I can edit it well I can just put a new tower into my existing tower so I want to place it just north of Mauna Carter if you can't see monocot so you don't know where it is simply just add in the OpenStreetMap it's just southeast of Peel honest I hope he lands back so this one a card so and it is in within one of those empty zones you want to call it that so dead zones I don't have coverage so I once you actually draw a tower just north of it so that is area is covered so I can just draw sour into that reclassed area that I was looking for that had the values of two so if you want to switch the visibility one off so the black points have values of two that I'd be interested in for example so one of those in this example would be to go there you want to go to your new tower you want the editors you want to create some new points there for example give it a unique ID switch everything else off and then you can rerun the tool that you had before basically so this money tower stop editing it is so what you can do now is you simply rerun the t-shirt so you create your viewpoints again using this information you run your visibility again and your outputs will be amended your view should will now be improved

Channel: GIS at UP

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Id: kC1ApQLcEhM

Length: 10min 14sec (614 seconds)

Published: Thu Apr 09 2020