5. Downloading SRTM Data from within QGIS

hey guys today we are going to go over the steps required to download your srtm data directly into your qgis session [Music] the first step is to load a base map in the background i'm going to reach for open street map grab it as a background and then i already stored my area of interest which is the toshka area in egypt toshka lakes the second step is to go to the plugins manage and install plugins and then search for the srtm downloader and then install the plugin now i would like to download srtm data covering this area of interest so what i'm going to do is i'm going to go to plugins menu and then i'm going to click on srtm downloader which has been added as a result of the plugin installation and then i'm going to pick srtm downloader dialog box the dialog box shows some text input boxes north west south and east these are the text input boxes where you should put the lat long of your area of interest or since we have already defined a of interest by using the spatial bookmark you can just set these numbers to the canvas extent so you click set canvas extend and it will pick up the coordinates the proper coordinates for you and then you need to determine the output path where you are going to download your data so i'm going to write media d and temp and then you click download now the first time you use this application it's going to ask you for a username and password if you don't have a username name or password in the site on the nasa site you need to go there and register and you can just click on that link and it will take you there once i input my username and password it will quickly grab all the srtm data for me covering the area of extent so now that the download is complete i'm going to click ok now because i have left the checkbox checked for load images to qgis i should find these loaded in the table of contents and they are loaded and if i zoom out a little my area of interest has been loaded so what i'm going to do next is i'm going to merge all these files into one file so i'm going to go to raster miscellaneous and merge and the first thing i'm going to do is i'm going to click on the ellipses here and i'm going to select all except of course the open street map and then i'm going to change the output data type into integer 16 and the other thing that i'm going to change is i'm going to change the assign specified no data value to output to the value of minus 9999 and i can choose to save the output merged file into a temporary file saved just in memory or i can give it a name so i'm going to choose to leave it as a memory temporary fine so i'm going to click run and here you go you have one single file instead of four different files so first off i'm going to remove the four files these are the hgt downloaded files from srtm you look at the merged file here and you see that small icon that shows that this is only a temporary file a temporary layer so it's not stored if you close the project right now even if you save the project the layer is gone so you have to save it so i'm going to save it export save as i pick the format jotif is fine with me i'm going to store it at the same place so it's media the temp and the file name we'll call it toshka ptm 30 and this one is 30 meter resolution now this is very important you can reproject it while saving it so i'm going to choose a metric a projection system instead of the the geographic coordinate system i'm going to use a metric system so a projected system that is so this is the one that i'm choosing it's a wgs 84 utm zone 36 north and the other thing is i'm going to change the pixel size to 30 meters by 30 meters and i'm going to add no data value again minus 9999 and i'm going to click ok now this is my 30 meter resolution digital terrain model for toshka i can go further and and color it so i can either click on the properties and color it from there or i can just click the style button here and i can choose single then pseudo color can go to ramp and i can choose either one of these ramps or i can say create new color ramp and choose catalog cpt city okay and then i can go to topography and i can either pick elevation or maybe pick this palette okay and classify and this is how it looks i can even go further so i'm going to actually i'm going to delete the temp layer remove layer and then i'm going to duplicate this layer so i'm going to duplicate it i'm going to actually switch on both of them change it to hill shade use a blend multiply i'm going to rename this one to [Music] dtm and this one to hill shade here you go so now you have your digital terrain model and it's even rendered then all in like five minutes and you don't have to go to websites that's all what i wanted to tell you this time thank you for watching and see you next time

Channel: The GIS Specialist

Views: 516

Keywords: GIS, RS, Remote Sensing, Geographic Information Systems, QGIS, ArcGIS, ESRI, Google Earth Engine, ERMapper, GEE, SRTM

Id: XHh3hQ-WN8I

Length: 8min 22sec (502 seconds)

Published: Thu Dec 31 2020