Dissolve in QGIS # QGIS Tutorial # QGIS Q & A

[Music] [Music] so [Music] hi guys welcome to this qgis tutorial in this video we'll learn how to dissolve features in qgis you can subscribe to this channel to follow all my previous useful js tips and tutorials if you like what we do here and you want to support this channel you can join our patreon i will provide a link in the description below dissolving is a process in which a new map feature is created by merging adjacent polygons lines or regions that have a common value for a specified attribute so let's go to qgis and look at today's exercise loop and qgis and before we start today's exercise i just noticed my copyright reads 2020 so we're going to do a very very quick adjustment to this so i'm going to go to view decorations then i'm going to look for my copyright label and then instead of voice jazz 2020 because you're in a new year i'll say 2021 then i click on apply okay and everything changes here so now that we have done that we're going to now go directly to what you're supposed to do today for today's exercise i'm going to load two layers so i'm going to go to layer add layer add vector layer then i'm going to browse where my vector layer is so i'm going to click on the browse button here and my data is in the desktop gis data then there is this dissolve exercise here and i'm going to load i have actually two layers here there's the world afric there's the wild countries and there's the african countries so i'm going to load both of the layers then click on add then click on close and now i have all my layers loaded in qgis so the next thing you want to do is i'm going to turn off the one layer first so i'm going to turn it off and then i'm going to zoom to the full view of africa share file so the next thing you want to do is you want to actually eliminate these boundaries that are within the african shapefile so that you can have just one continent continuous continent for the whole of africa so how do you do that you're going to perform at your processing function called dissolve so i'm going to go to vector it's under vector your processing tools then i'm going to select dissolve when you select dissolve this pop-up a logarithm appears so i'm going to input my layer which is the african countries then i'm not going to dissolve it to any attribute here first or any fields i'm just going to create a temporary layer for my first result so what i'm going to do is i'm just going to click on run and it pretty much takes very short time to run and you can see the algorithm has finished the dissolve has finished so let's look at our results and click on close and you can now see we have one big polygon of africa without the boundaries when i open the attribute table it actually just takes one of the attributes so it's upon use as the user to just edit and just edit the information that is here and even do a new calculation for the area because i believe the area will be much bigger here so that is the first way of dissolving this you can see we have one continuous polygon now let's look at the attribute table and see how we can this we can also do the result function so i'm going to go to right click on the layer of africa again then open the attribute table and then look at the attribute table and you can see my attribute table i have the names i have so much information here but i'm interested in another thing here and it's called there the region you end region you can see there is the middle of africa eastern africa there's the west africa so i actually want to now dissolve them according to this region of the eastern africa the middle the northern africa southern africa and western africa so we're going to be using this field to dissolve our african shape file so i'm going to close the attribute table then i'm going to do the same thing which is i'm going to go to vector your processing tool dissolve i'm still using the african countries as my input layer then the dissolve field now we're going to select it from here so i'm going to click on this so that i can actually look at what the all the fields that are within the layer so i want to dissolve it using there the un region one i'm going to select that as the field that i'm going to be using to dissolve my results so after selecting that i'm going to click on ok then i have one option selected in under the fields so i'm going to just dissolve this and create a temporary layer again and then let's look at what happens so i'm going to click on run you can actually just save them to file if you're sure about what you're doing but i want to just look at my results first before i now make the my layers permanent so i'm just going to click on run and it pretty much takes a very short time to run let's just wait for the process to run and you can see the dissolved results have finished and then i'm going to click on close and now i have another dissolve here so let me just turn off my first temporary layer and you can see in my second temporary layer now i have dissolved the african regions using the region that we had actually selected so i'm actually just going to look at the attribute table to see the regions so i'm going to open the attribute table and you can see now when i scroll i can actually see the uan regions have the eastern africa middle africa west africa north africa and south africa i can decide to symbolize them so i'm going to go to right click on the layer go to properties then i'm going to symbolize them using their categories un regions one you enrich once then i'm going to say i'm going to use can random colors click click on classifier and i have all my my regions here and i'm going to click on apply okay and you can see now they have been classified according to the different regions you can see east africa is here middle africa is this northern africa is the top part here west africa and then the southern africa so that is how you dissolve now using the using a field in your attribute table so you can actually decide to make this permanent now then do your edits and use it in any analysis that you want to run so the next thing we want to do is i'm going to actually uncheck the two i'm actually going to remove the two dissolved because we have already achieved what we wanted i'm going to remove them remove the layers and i'm also going to remove them and check the african continent now let's now use the whole world data and look at just how we can just dissolve the different regions in qgis i'm going to zoom to layer and this is data for the whole world so we're going to just look at the attribute table first and see what kind of information our data has so i'm going to open the attribute table by clicking on the layer going to open up to be table and then you can see we have the name the country the english name of the of that then the sovereignty the continent then there is the un region the first thing you want to do is you want to now dissolve using without necessarily using any of these columns here so i'm just going to go to vector again your processing tools dissolve then right now my active layer which is my input layer is the world countries then i'm going i'm not going to put any option here i'm just going to create a temporary layer for now then i'm going to click on run and the process starts our dissolve has finished so let's look at the results so let's close this and you can now see when i use the select tool to select it actually selects the whole region and now we only have one one row that is now the whole world so let's now look at another way of now dissolving this so this one can just be now renamed to this is the world share file so we have a wireshare file which is still a temporary layer we can actually save it later on so we want to now look at how to to dissolve in another way let's look at our attribute table and now you can see we also have another column here called continents so actually we can dissolve this data according to continents so let's try and do that we'll go to vector again your processing tool dissolve we are still using the same world country share file then the dissolve field you're going to click on the three buttons here and then we're going to select the continent as our dissolve field then okay then i'm going to click on run so that you can actually get our results so we're just going to wait for our results the logarithm is finished so let's look at our results and then click on close and now we have a new ship file here called dissolve when i look at the attribute table now you'll see it has now been divided into the five continents in the world you can see oceanic and north americans of america asia and europe so let's first style that go to properties so we can symbolize that using the categorized then the value that we're going to symbolize is the continent we're going to just use random colors and click on classify and we have our different con continents here in different colors click on apply okay and now you can see if i uncheck these we actually have all the different containers you can actually even decide to name them i'm going to label them using a single label then you're going to use the continent then the text is going to just be black much bigger then with the white buff for the background then click on apply okay and we have our results you can see those americas america africa asia europe oceanic so that is how you perform dissolved so we have moved from these which has boundaries to these which has actually now the which has now the continents so you can actually do this for any kind of data be it maybe for example you have land use land cover data and you want to just show the different classes in one column you can actually just use this dissolve tool to dissolve those attributes so we can now rename these two we can rename it to wild continents so now we have two temporary layers one is the for the wall shape file and which is actually for the whole of the world and then now we have now another ship file that has the continents and now our initial ship file has now all of the world countries that's it for today's exercise if you found this video useful and you want to learn more on qgis subscribe to my channel don't forget to give this video a thumbs up otherwise i'm just happy you're here see you in my next video

Channel: WiseGIS

Views: 480

Keywords: qgis, #qgis, qgis tutorial, qgis tutorial for beginners, qtips, vector data, gis, how to dissolve in qgis, vector geoprocessing, vector geoprocessing tools in qgis, remote sensing

Id: EwwxfK5PYWs

Length: 14min 14sec (854 seconds)

Published: Thu Jan 21 2021