Creating Spatial Distribution Maps in QGIS #QGIS Tutorial

[Music] [Music] [Music] hi guys welcome to this tutorial in today's lesson you're going to learn generating maps showing spatial distribution in qgis we're going to be using spatial interpolation to effect this process so what is partial interpolation special interpolation is the process of using points with non-value to estimate value at other points it can be used to predict unknown values for any geographic point data such as elevation rainfall chemical concentration and noise levels the primary use of interpolation is to help users be they scientists photographers engineers or mathematicians determine what data might exist outside their collected data in this exercise we'll use a csv file that contains support concentration of different heavy metals like for example the mercury cadmium ascenic chromium thalium and lead to generate maps showing special distribution of heavy metals in urban soil so let's get to today's exercise so it'll open my qgis and in my qgis project i already have our area of interest that is 34 kilometers squared and i also have some line data for the rivers that pass within our project area so with yesterday of the rivers then we need to introduce the data that you have collected from the field and i already have an excel file that has all the data that you need for this exercise there's a sample location then there's the concentration of mercury lead copper chromium cadmium zinc nickel acetic and also we have the longitude and latitude that are very very useful for us to be able to introduce this kind of layer into a kgs project so i'm going to save this layer as a csv file it's currently an excel file so i'm going to go to file save as then i'm going to save it in our distribution map folder and i'm going to call it the heavy metal concentration that is heavy metal heavy metal concentration sample and it's a csv so i'm going to click on save and i can save it in that folder then now that i have already created my csv layer i'm going to go back to qgis and i'm going to introduce this layer into qgi into our kgs project so i'm going to select layer i'm going to add a layer and i'm going to add a limited text layer because i'm bringing that delimited text to the csv file then i'm going to browse where the limited text layer is and it's in my distribution map exercise the heavy metal concentration sample i'm going to click on it and then click on open then i have a preview of how my sample data looks like including elongated and latitude and considering that this is a it has a coordinates i'm going to select point coordinate and by default it it pre pre-assigns the x field to longitude and y field to latitude if that's not the case for you just click on the drop down and select the x field longitude and wi-fi latitude so the next thing you're going to do is you're going to look at the crs and you can see i'm going to project it according to my project crs which is 32 737 that is utm zone 37 north which is the same as my project crs down here so i if if if actually your project series your crs are different you just need to have the same projection so after that i'm going to click on add then i'm going to click on close because they have been added and you can see now these are the points the csv data that we collected in the field now in the region of interest so i'm going to save this as a permanent layer to save it as a permanently i'm going to right click on it because it's currently just a csv file then i'm going to export save feature as and i'm going to save it as an sshf file you can judge it to any other file you like but i'm going to use the sd shift file so i'm going to click on browse and i'm going to save it in my description map exercise folder again going to create a new folder i'm going to say ship file and i'm going to save them within the shapefile folder and i'm going to say this is the heavy metal concentration and i'm still going to use the same projection for my layer and my project and i'm going to say okay and now i have my heavy metal data contractual shapefile so i'm going to remove this csv and i'm going to right click on my layer to see an open attribute table to see if all my data was imported successfully and you can now see i have my sample location with mercury lead copper chromium cadmium zinc nickel and arsenic including the languages and latitudes which are in utm so now that we have our data here we're going to learn how we're going to create these nice concentration distribution maps for each and every element within our attribute table so we're going to start with mercury so the first thing we can do is actually we can actually label them according to the different sample locations so i'm going to right click on this layer i need to go into properties then i'm going to go to labels and i'm going to show the single labels and i'm going to label them using the sample location and we're just going to create a nice buffer make sure the text is a dark color then placement i'm going to place it maybe to a distance of maybe say two millimeters away from the point and i'm going to click on apply okay and we have all the sample locations within our area of interest so the next thing i'm going to do is i'm going to introduce a bezema so to introduce the base map i'm going to go to the hmes plugin i'm going to go and select bezma then i'm going to go and select the google satellite or google satellite hybrid because i also want to see the labels within my my data so i'm going to select that and the google hybrid setting is actually loaded very quickly and you can actually now see the region of interest where i actually collected the data and it's somewhere around some industrial area in nairobi you can see this is an industrial area so we want to just see the concentration level of the different heavy metals within this area of interest and to be able to create very nice special distribution map we're going to use a tool called the interpolation tool so to get interpolation tool you can go to the processing then select the toolbox and then under the processing toolbox you can just select interpolation and you will select there are several ways of interpolation but you're going to be using the idw interpolation so i'm going to select the idw interpolation so we're going to start with the first method which is mercury and the vector layer that we're going to be using in this exercise is the heavy metal concentration data and it has already been loaded here as a vector layer then the interpolation attribute is the attribute of mercury so i'm going to select first the first interpolation attribute which is mercury then i'm going to click on the plus button here to input the layer green plus and actually i'm going to be using point points for my mercury data you can you have an option of structure lines and break lines but you're going to be using points then the coefficient distance i'm going to leave it at 2 the extent that we want to make our uh distribution map is i'm going to use the our project area which is nairobi so i'm going to select the select i'm going to calculate using our project area which is project survey area nairobi then i'm going to change the pixel size instead of 0.1 i'm going to say 1 for x and 1 for y then i can save it as a temporary file or i can save it to file so i'm going to just save it to file somewhere so i'm going to click on that then click on save to file then i'm going to save it in my work folder create a new folder in my work folder and call it raster because they're going to be generating raster files from these point data then i'm going to say this is mercury mercury concentration it's a tip file and then click on save then i'm going to click on run and wait for the process to run the task is complete so i'm going to just look at my results and you can see i have some results here for the mercury concentration in my area i can just move it a bit down and then we're going to do a symbology of this so that you can actually make sense of the kind of data that we have so i'm going to it's currently just a gray scale so i'm going to select mercury click on it go to properties then under the symbology i'm going to say single boundary instead of a single bond brace care i'm going to select single band single color and i'm going to look for a color ramp that i'm going to be using in this exercise so i'm going to select under my color amps here and you can see i have a color ramp of concentration that i actually created i'm going to select that color ram and then the labels i'm going to put them into two decimal places and then i'm going to let it be continuous and the interpolation first i'm going to use instead of linear i'm going to i'm actually going to use linear for the first uh kind of uh analysis and then i'm going to click on apply and okay and you can now see the highest concentration which is red in color in these regions here and the lowest concentration which has brown color of mercury are in these regions here i can even introduce the rivers and you can actually see actually it is where the rivers pass and there's low concentration of mercury in these areas and this area being an industrial area maybe might have been the contributing factor to having high concentrations of mercury here we're going to do the concentration of all the other metals but heavy metals but before you do that i'm going to just change something in my style here in my symbology here so you can actually look at and see what will actually suit our analysis so i'm going to go to up to the properties again then instead of interpolation being linear i'm going to select and say i want interpolation to be discrete and i want everything else to remain the same then i'm going to click on apply okay and now this is how the discrete looks like you can actually see there's less than 0.8 and there's a greater than 2. four as the highest so depending on how you want to view your results it is up to you to decide if you want to use the discrete or you want to use the linear so i'm going to do that for all the other heavy metals using the same same procedure and then we're going to create different kinds of maps and be able to just look at the different special distribution map so i'm going to go to the next metal which is uh let me just look at the attribute table so i'm going to go to lid and i'm going to do that for all these other kinds of heavy metals so i'm going to go to lead now i'm going to open i'm going to uncheck mercury then i'm going to go to the interpolation again adw interpolation then i'm still using the heavy metals concentration data then i'm going now to select lead then i'm going to do the same thing i'm going to click uh the green plus button to add it in the vector to add in the vector layer and its points then the coefficient is going to be true the accent is still going to be the same i'm going to use the survey area that is nairobi then i'm going to make the pixels one to one and then i'm going to now save it as a file in my work folder i'm going to save it to files i already have the mercury i'm going to say this is lead concentration and then i'm going to click i'm saving i'm saving it as a tip file click on save then i'm going to click on run we are done with the interpolation of all the heavy metal data and we have the results here for all the metals from mercury sonic nickel zinc cadmium chromium copper and lid [Music] [Music] you

Channel: WiseGIS

Views: 609

Keywords: qgis, gis, spatial distribution, maps, heavy metal concentration in soil

Id: UeFzSqg0yso

Length: 16min 24sec (984 seconds)

Published: Tue Nov 02 2021