Page 1Page 2Page 3Page 4Page 5Page 6Page 7Page 8GEO/EVS 425/525 Unit 1The ERDAS Imagine Viewer and File TypesERDAS Imagine is an extremely powerful Geographic Information Systems program oriented toward thedetailed analysis of satellite imagery and other complex raster data sets. There's good reason that it hasbecome an industry standard for raster-based GIS analysis. It is capable of environmental modelingbased on input data of several sources with complexity ranging from very simple to extremely complex. The key to using the ERDAS imagine is the viewer. The viewer is the graphic window to whatever imageyour dealing with. It is opened automatically whenever you learn enter Imagine. You can open as manyviewers as you want (within reason), and you'll be able to link viewers to carry out some very interestingsorts of analyses.ERDAS Imagine is capable of handling a wide range of file types. It is necessary that we distinguishamong two different classes of file types: native and importable. To say that a file format is native toImagine implies that the file can be read directly by the core software. Not only that, if you're saving animage, this is the format in which that image will be saved. There are two native formats. For rasterimages, the native format is the Imagine format. Image files have a .IMG extension. For vector images,the native format is the arc coverage format used by the industry-standard vector software packageARC/Info. Image components are stored in directories rather than individual files. Each image will haveits graphic component stored in a directory with a name corresponding to that of the image in question,and it will have its data stored in a directory named "Info." As indicated above, you are not limited to those file types that are ERDAS Imagine raster files or ARC/InfoArc coverage vector files. Other files can be read directly by the Viewer, and still others can be importedinto Imagine and then read. ERDAS Imagine can import a very large number of different formats – farmore than you are ever likely to use in your life. Even so, there are some formats that it cannot import. Noremote-sensing software can be all things to all people! Some of the form ats you will encounter in thiscourse are very important, however, so you need to be able to use the import and export functions ofImagine. Basically, you import files from a non-native form into the native raster or vector format, and youexport files from the native raster or vector format into whatever format you desire.In this laboratory, you'll learn the most common activities of the viewer, and you'll learn to deal with bothnative formats, and you will import a SPOT image. First, however, you need to learn some basic thingsabout ERDAS Imagine. Opening ERDAS ImagineTo open ERDAS Imagine, click on the icon labeled "ERDAS Imagine" on the desktop of any of thecomputers in the lab. This will set up the network and call Imagine. W hen imagine first opens, you'llnotice that it takes a while for anything to appear on your desktop. Imagine is a big program, and it takesa while for it to load. Two things appear on your desktop. The first is the main control bar, which appearsat the top of the screen. It contains a menu bar with five items: Session, Main, Tools, Utilities, and Help. You should click on all of these and determine what is there. Most of the menus that open up when youclick on one of the items in the menu bar won't make very much sense to you right now, but it is importantfor you to have at least a feeling the what is there. Below the menu bar, there is a series of icons enablingyou to do different things. You will not use all of these icons in this course, but you will use most of them.The second thing that opens up is the viewer. Imagine actually has two types of viewers. The simpler iscalled the “traditional viewer”; the one we will be using more commonly is the “geospatial light table.” W ewill refer to both types as “viewer.” The first geospatial light table opens automatically; it is labeled"Viewer #1". However, you can open up as many other viewers as you want to by clicking on the viewericons in the main control bar. You might try this and open another viewer or two. Alternatively, you can goto the “display” section of the viewer and click on one of the 4 icons. You will notice that other viewerwindows open within the single geospatial light table. This can be a very useful feature.All viewers contain a menu bar with 6 items: File, Utility, View, AOI, Interpreter, and Help (Figure 1). Beneath the menu bar is in icon bar containing 17 icons (Figure 2), most ofwhich you will need to become quite familiar with. Note that both themain control bar andthe viewer have threebuttons in the upperright hand corner(Figure 3). These are the standard buttons found in this position in most W indows programs. From left to right, the small underline will minimize the object in question. This means that youwill no longer see the object on the desktop, but the button corresponding to it will remain on the status barat the bottom of your screen, so that you can bring it back by pressing this button. Try this with the mainImagine control bar: press the minimize button, and the control bar will disappear for the desktop. Pressthe button on the status bar at the bottom of the screen labeled IMAGINE, and the control bar reappears. The next button to the right, the Square, maximizes the object in question, so that it takes up the entiredesktop. Again, you might wish to try this with a main control bar. You'll notice that when you maximizean object (and this is true of any object), the "maximize" button changes to a different form. Actually, whathappens is that it disappears and is replaced by the "Windows" button. Press this, and the object returnsto its normal view. You will probably never want to maximize the Imagine control bar. But you're verylikely to want to maximize the viewer. The last button on the right, the x, it is the "close" button. When youpress it (and don't do it for the main Imagine control bar), the object whose "close" button you havepressed disappears permanently. Try this with the viewer – and then reopen it.Some Details of Directory StructureBefore you actually open in image, it's useful to get a feeling for how your directories are structured. Clickon Session on the menu bar of the main Imagine control bar. From the