Creating DEM in QGIS # Lesson 17 of 29 #QGIS Tutorial

[Music] [Music] hi guys welcome to this qgis tutorial lesson 17. in this video we will learn creating dem and contours from point data if you haven't subscribed to my channel please do so so that you can get a notification when i upload my next video if you are new to my channel you can follow all my previous lessons and useful gis tips from the links in the descriptions below let's get started so today we're going to build to learn how to to create dm and controls from points so what we need is point data first that has elevation and then we will use this point data to then to generate a dm and later on we'll use the dm now to create very nice contours for our area of interest so we're going to be using the google lab software to get the points data then the gps visualizer to just make sure that the point data has the elevation values then we will use the gpx segmentalities of qgis plugin to load the point data that we have uh actually assign the elevation values and then we're going to use the interpolation idw interpolation to create our dm raster so let's get started so let's go to google apps and learn how we can create this point data so i'm going to open google app pro then i'm going to search for my region of interest you can actually just manually search but i'm interested in a region in nepal so i'm going to just type nepal hit enter but i get the precise location where i want to have it as my area of interest so i'm just going to zoom in to nepal and you can see in nepal there is this region here which is very very hilly that i want to get the dm off i will add a path so i'll go and click on add path so this is my area general area where i want to have my dem for the area so i'm just going to click on add path then i'm going to call this path nepal nepal points can you even change the state the color of the or the feature and even change the size and i'm going to just move it aside and i'm going to make a point a line here so i'm just going to draw a line you can actually draw in any direction so i'm just going to draw a line like this so i want to have the dm of maybe say this area and i'm going to just draw the lines like that there is no uh specific way you are supposed to just draw the more points that you have the better so the more accurate your dm will be so i'm just going to draw the lines to cover the whole of this area so i'm satisfied with the number of points that i've created so i just now bring back this new path and then i just click on ok it's nepal points click on ok and i will have my nepal points here so what i will do i will now then save these places as a kml file so click on save places as then look for where i want to save my kml file which is in the data in the gis data folder and i'm going to create a new folder here and i'm going to call it kml i'm going to save any powerpoints it's a kml file you can just leave it at kmg no problem but it's a kml file so i click on save and i have my kml file now the next thing we need to do is we need to now go and use the gps visualizer to make sure that all that is assigned the elevation values all that the the nepal points is assigned the elevation value so we'll open our browser and then in our browser we'll type gps gps visualizer i'll leave the link in the description below for this and this says find missing elevations with gps visualizer so i'm going to upload a file here so i'm going to click on choose file and i'm going to find where there where actually i saved my my kml file that is under data kml and i have my nepal points here so i'm going to select the powerpoint open and i have loaded the default points here so i'm going to click convert and add elevation and the output is a gpx file you can actually save it as pain but i want to save it as a gpx file because i want to load it into qgive so gpx file then i click on convert and add elevation give it a few seconds to do that for me then you can see now an overview of my nepal points here and you can see an elevation has been added here so it's a very very long gpx file which has elevations so the next thing i will i'll do i'll click to download these gpx file i'm going to then i'm going to save it in data desktop gis data i'm going to call it new folder i'm going to say gpx files and i'm going to save these as nepal points so it's a gpx file i click on save and it has finished downloading my gpx file it's just you can open it with notepad to confirm if you have the elevation values now after doing that the next thing we want to do is we want to bring it into qgis so that you can create our nice dem so we're going to go to qgis and in qgis the first thing you need to do is you need to install a plugin and the plugin that you're going to install is called the gpx segment tool so you can see i've already installed the gpx segment tool here but for you you can just go to manage and install plugins then under all you can look for the gpx segment importer then you can actually install it for me i've already installed it so i have no problem but for you you have to install it so i click on close then it will be loaded under your plugins and you'll have the gpx segments tool here under your plugins so we want to actually bring our nepal gpx file so we're going to go to click on plugins now select the gpx segment tool and select the gpx segment importer then you're going to select where the file is so i'm going to click on select file then i'm going to select where my nepal file is which is under gis data and it's a gpx file so gpx file and i will only have this gpx file so i'm going to select that nepal gpx trucks then it will be loaded here and you can see an example of how the attribute tab will look is like this it will have an elevation which is a floater double then the example is these so i'm just going to click on my output directory or i can just click on ok to save it as a temporary file so what i'll do is i'll save it as a temporary file first and i click on ok and you can see it has loaded the gpx in qgis here it's just a very very very a line that is zigzag all over so we need we can actually look at the attribute table first to see what we have and then you see the attribute attribute table has the elevation but what you want to do is you want to first convert these line into point data how do we do that we go to a vector then we come to the geometry tools then under the geometry tools we'll come and select extract vertices right so i will select extract vertices and what what vertex do you want to extract we want to extract them from the nepal gpx points so what i will do i also create these as a temporary file i'll click on run and within no time i click on close now i have my vertices and i open the attribute table of the vertices now you will see it has the elevation which is very important it has the vertical index and all these other information including the distance and angle but they're not interested in these other statistics we're just interested in the elevation values or the points now let's go to the third step which is very very important we now have our vertices we are good to go we want we want to now convert these points into a dm the next process we're going to do is we're going to go to the processing toolbox then in the top processing toolbox we can actually just search for the id w interpolation and you can see there is interpolation and the idw interpolation here so i'm going to select double click on iw interpolation and then now the next thing the parameters that you're going to put is there which is the vector layer are the vertices right the ones that we have actually created the interpolation attribute is there elevation remember we want to use the elevation as that then we're going to click on the green plus button to add it into into our work area so and the vertices attributes and what what type of are we using we are using the point you can actually use the structure lines or black lines it doesn't matter but for now we're using the points each other vertices then the distance that is i leave it at 2 the extent i'm going to just use the vertices as the extent then the number of rows i'll change them to maybe say 50 then columns 77 it will actually generate rows and columns that so i'm actually increasing the number of rows and it will increase the number of columns so that we have a better result and i'm going to just click on run and then i click on close and i have my very very very nice raster layer loaded now in qgis so i'll uncheck on this and we can do a little bit of styling on my dm consider the dm so how do we do a styling of dm.properties then we go to symbology select pseudo color then i'm going to now select a color ram so i'm going to create new color ram and i'm going to use the catalog cpt cpt cities because i want to have the color ram for for topography then i'm going to select topographically you can actually have very very many more kinds of elevation very very many more kinds of how you can actually do your color ramp so i'm going to select topography then elevation then i'm going to click on ok then i'm going to now classify my my my dm so i'm going to click on classify and then i'm going to click on apply okay and you can see now we have a very nice dm showing the black region at the high points then the the brown regions and all that so this is your tem data now the next thing we need to do is we need to generate controls from this how do we generate controls from this we go to now to rasta then click on extract and click on contours so we want to extract the controls for this region we're going to use that because it's the only raster data available to you that interpolated if you have many raster layers loaded on your layer panel you can actually just select the one that you want to use then the interval i'm going to say maybe say 100 then what attribute are we using and using the elevation then i'm just going to click on run and just give it a few minutes to load and then you can see now the process is finished they come the contours has finished so i'll click on close and now you can see we have very nice contours generated or area so when you open the attribute table you can actually see the contours of the elevation value which is very important and you can just decide to name our contours to label them so i'm going to click on label then i'm going to use the elevation value then i'm going to leave it as a text and maybe just change the color to that because i haven't actually used any of those colors and then and i zoom in you can actually see the elevation values of my region of interest so that's how you generate contours from point data if you found this video useful and you want to learn more on qgis subscribe to my channel hit the bell icon so that you can get a notification when i upload the next lesson otherwise i'm just happy you're here see you in the next video

Channel: WiseGIS

Views: 1,186

Keywords: qgis, qgis 3.14, qgis3.14pi, dem, contours, interpolation, idw, opendata, foss, qgis tutorial, qgis 3, qgis 3.14 tutorial, gis, qgis tutorial for beginners, arcgis tutorial, arcgis tutorial for beginners, arcgis, raster data model, digital elevation model, digital elevation model in gis, qgis plugins, qgis plugin development

Id: 1qUYqUFGiB0

Length: 16min 48sec (1008 seconds)

Published: Mon Sep 21 2020