Downloading Landsat 8 satellite image data to use in a GIS

I'd like to show you how to download Landsat 8 satellite imagery from the United States Geological Survey website you can just do a search online for USGS Landsat 8 data something like that if you want to find it or you can go to the URL earth Explorer USGS gov either way you'll I'm sure you'll be able to find it and so that will bring you to this interactive web Explorer type interface where you can zoom and pan to different parts of the world search for satellite imagery and then download it so I'm going to search for San Francisco just type that in hit enter and you'll see that that comes up right away so I'm going to click on that and so that's showing up on my map so I can zoom into that area now I can optionally put a date range in here I believe what it will do is list the results in reverse chronological order and since I'm interested in recent data I'm not gonna bother putting in a date range there but you could for example say I'm only interested in you know imagery from July or August from 2016 or whatever it happens to be I'm just gonna leave that blank and click the data set button so that opens up a list here I can expand the Landsat options and I'm going to go with Landsat collection 1 level 1 if I expand that I'm going to select Landsat 8 and so now I'll click the results button so here on the left you can see the different imagery that's available that meet the criteria that I've specified so this is for the San Francisco area I didn't set a date so it's given me lots of different options here as you look at the results of your search a couple of things you may want to keep in mind or the time of year and the amount of cloud cover that there is so depending on what it is that you're trying to map you may want to have say the vegetation in full leaf because that's what you're interested in looking at so that might mean getting an image from the summer months or maybe you don't want the leaves to be on the trees you want to be able to see the ground underneath then you might want something from the winter months unless of course you live in an area that has a loved snow then in the winter all you're going to be able to see you snow and so that's not gonna work so you may want to go with a spring or fall so that's definitely gonna be a factor is what time of year you want to look at and also cloud cover when you look at when you're using something like Landsat 8 that's of using visible and near close to visible wavelengths that are affected by clouds so in other words they don't penetrate clouds and so if there's cloud cover over your image then you're not going to be able to see anything under those clouds so when you look at the thumbnails you can easily see major amounts of clouds you can also filter the imagery for cloud cover if you want so that's just a couple of things that you may want to keep in mind as you look through the results so if I scroll down here I see some imagery from September here's an image that looks like it has a lot of cloud cover in it because you can actually see the clouds off the coast I think that's pretty common in San Francisco and if I keep going I see one here from June 1st 2018 that looks like it might be a pretty good candidate so a couple things I'll just mention is you'll see this little footprint here if I click that then it will show me the coverage of that image so that's the footprint on the earth of how much of that image covers the earth which can be extremely useful especially you know it's common that you'll have a study area that spans more than one image you want to make sure that you get all of the images that you need for your project if you click show browse overlay and if I turn off the footprint that will actually give you a quick snapshot of what that image looks like which is another quick visual wave being able to make sure that it looks the way you expect it to and whether or not there's any clouds present and then I can click here for download options so you'll notice there's a dialog box that's popped up here that gives me different options for downloading but that it's asking for me to log into my account in order to complete the download process you have to have an account in order to be able to download data it's free it's really easy to set up I'm not going to walk through it here I already have an account so I'm going to log in and then continue with the download procedure so you notice here that there are different options for downloading the first few are really just to download a snapshot of the satellite image so you one of the things that will kind of tip you off is that when the image is only six megabytes it means that it's really just kind of a it's not a full full resolution multispectral image it's just as a little tiny JPEG picture that you can use for reference later if you want to the full data is the one at the bottom here if we click download level one geo TIFF data product you'll notice that it's nine hundred and ten megabytes that's what will tell you that this is the full data set something something that's a large number like that I'll just go ahead and click download so you can browse to wherever you want to store that file I'm just going to keep it here on my demo drive and you'll notice the file name is fairly long that's including information about the the image itself so things like that are embedded in here or the file on the path and the date and so on and you also said it's a TA r dot G Zed or gz file extension so that's a tar or a tape archive file format and GZ D means that it's being compressed so we can download that but we're going to then have to use a utility to be able to convert it from a tar format into one that we can use inside our GIS software so I'll click Save so as this file is almost a gigabyte it may take a few minutes to download depending on your internet speed your bandwidth okay and through the magic of editing I sped up that little process here's our completed file as you can see this is a tar.gz file format what that means is we have to take it out of that tar format so that's a format that's used to kind of collect a bunch of files and put them together in a similar way to a zip if you're familiar with that so we have to take it out of a tar format and decompress it by taking it out of the gzip format so the utility that I like to use for this is called 7-zip it's free you can download it and it's straightforward and it's one of the few utilities that I found that you can easily convert 8r format and decompress very simply so I'll show you how that works so since I have that installed already all I have to do is right-click on this file and you'll see that I have 7-zip here and I can say extract here and that's been completed and you'll notice that this file is now about 1.7 gigabytes so what that's done is it's uncompressed the file or decompressed I'm never quite sure what the right way of saying that is but it's expanded it let's put it that way and so now we've taken our compressed dataset we've expanded it so now that it's the full dataset so it's no longer got the GZ at extension but now we still have to convert it from a tar format so we just right-click again select 7-zip and then say extract here so now we've decompressed it and we've converted it from the original tar format into the actual image files that we'll want to be able to access and use in our GIS software this may take a couple of minutes because these are fairly large files they're raster they're satellite images so they're fairly big but be patient and it should hopefully work correctly and now it's complete which is great so these are all the files that were bundled up and compressed and put together packaged up for us by the USGS now we've turned them into a format that we can now use inside our GIS software

Channel: Don Boyes

Views: 26,912

Keywords: gis, arcgis, donboyes, introduction to gis, landsat, satellite, landsat 8, remote sensing, download, satellite image

Id: 1ytgbKs93Kk

Length: 8min 9sec (489 seconds)

Published: Mon Sep 16 2019