Page 1Page 2Page 3Page 4GEO/EVS 425/525 Unit 13Obtaining Remotely Sensing ImageryRemote sensing is a field that has grown incredibly in the. last few years. As recently as 20 years ago, onlyone general-purpose satellite was functioning, and that carried only coarse panchromatic andmultispectral sensors. Now there is almost an embarrassment of riches to chose among, and differentsatellites carry sensors of widely differing characteristics. In this exercise, you will search out and find atleast three different satellite images of "interesting" places from at least three different satellites, and youwill download one entire Thematic Mapper image. You should also think about the relative advantagesand disadvantages of each satellite. Most of you should choose the Cuyahoga River watershed betweenCleveland and Akron, although you are free to choose any area in (or near) Ohio. The satellite systems from which you will choose are on the "links to neat places" page of the olddepartment web page (http://www.bqes.csuohio.edu/Iinks.html).' You should definitely plan to include oneLandsat-7 image, one SPOT image, and at least one of the images obtained from Spacelmaging (i.e.either an IRS/LISS image or an Ikonos image). You will download an image from the OhioView web site;this will be a Landsat-7 image.For all of these sites, you should look at the prices charged for each image. You will notice that the sitescan provide imagery in several forms. The basic unit is the scene. Some sites offer subscenes; others donot. Also, you can get data raw, partially massaged, or massaged more completely. You should askyourself what level of massaging you would find most useful, and what forms of the data are most cost-effective.The search sections of all of these systems has on-line documentation and usually a tutorial as well.However, they are all so idiosyncratic that they border on the useless. Hence rough instructions on the useof each system are given in this handout. If they are sufficiently detailed, you should be able to getinformation fairly easily. Otherwise, you should consult the "help" files available on the WorldWide Web.USGS SitesThe USGS has two main data gateways for satellite imagery. They are the EarthExplorer site and the EOSData Gateway site. Both do approximately the same things.Go first to the EarthExplorer site (http://earthexplorer.usgs.gov). Note that you will need to use InternetExplorer or Netscape 4 for this site; Netscape 6 will not work. Assuming that you do not have an accounton EarthExplorer, click on "guest" to log in as a guest. You will need to provide some information to thesite in order to find imagery.First, you have to indicate a location. The easiest way to do this is to click on "enter coordinates" andindicate the imagery you want by latitude/longitude. As a reference, Cleveland State University is roughly41° 30' N, 81° 40' W . You can indicate either a point (i.e. a single latitude-longitude pair) or a rectangle(i.e. two latitude-longitude pairs, indicating diagonal corners of the rectangle) as your location. The searchengine will look for all images containing any part of the area you have indicated.Next, you have to indicate a data set. You have several data sets to choose from. Concentrate on satelliteimagery. You should definitely choose Landsat-7 (also known as Enhanced Thematic Mapper Plus, orETM+), and you can include any other imagery you wish. Feel free to choose anything that soundsinteresting. You aren’t paying for the imagery (yet)! Indicate your choices by clicking on the square to theleft of the name.When you have chosen your location and data set, click on "continue." You can now specify several otherlimitations on your search. You may want to limit the dates to be searched (but you do not need to,especially if you are searching only for Landsat-7 data, since it will not search for data that do not exist),and you will certainly wish to limit cloud cover (for general use, you should limit imagery to less than 10%cloud cover). You will probably also wish to specify more than 10 images to be reported (50 is a goodnumber). You can leave all of the other fields at their default settings. When you have completed yoursearch criteria, click on "search." The search engine will go through the USGS data base and report thenumber of images meeting your search criteria.To see what you've gotten, click on the name of the data set. You will get images reported in groups of 10.Look at the information reported at this point. To see the browse image, click on the "show" column for theimage that you're most interested in. Pick one of the browse images. If it shows the detail of the area youwant, make sure that it is not already in our collection on the R drive. You will be downloading this imagelater from the OhioView site. Record the file name (i.e. path, row, and date), and print the browse image.The other USGS site is the USGS EOS Data Gateway (http://edcimswww.cr.usgs.gov/pub/imswelcome).Enter the data center as a guest by clicking on Enter As Guest. The search procedure is a 4-step process.You must first Select Search Keywords. You should use Method 2. Click on "sensor", then "select." Youdon't need to use a filter, but if you want to, choose "visible sensors." Choose your sensor. Landsat-7 islisted as Landsat ETM+. Note that this site has a great many more satellite images than the EarthExplorersite. Choose your sensor and hit OK.The second step is to choose your area. Here you indicate an area you wish to search for, again bylatitude-longitude. Note that this site does not have a field for North or South Latitude or East or WestLongitude. South latitudes and W est longitudes are indicated with a minus sign. You probably don't haveto worry about South latitude, but most of you will need to look for West longitude.The next step is to indicate the date range. The issues here are as they were with the EarthExplorer site.The default (standard date range) will probably suffice for your search. Finally, you need to indicate theother options you wish to consider. The basic options are given. You might want to look at the "all options"page to see what options exist beyond the basic, but you probably won't want to use them, Note that youcan't specify a maximum cloud cover figure. You will have to get this information from the informationreported back to you.The actual search and the information reported back to you are essentially the same as