![]() Close the Spatial Profile table and click again on the graph button in the Viewer toolbar. The next exercise will use the Spectral Profile Surface, which is similar to the Spatial Profile, except that it is in 3D. To stop drawing the line and to display the results on your graph, double click with the left mouse button.ĩ. Each time you want to change the direction of the line click on the left mouse button. On the image, click once with the left mouse button to start drawing a straight line. A similar looking window as for the Spectral Profile will appear however, notice the the axes are different.Ĭlick on the line button. Click again on the graph button in the toolbar in the Viewer window, but this time choose Spatial and hit OK. Close the Spectral Profile window to get rid of your profile points. This part of the exercise shows you how ERDAS can help you visualize how different wavelength reflect along a transect of the land surface. With your new knowledge about the spectral profile for a given feature, you can go back and change your band combinations to make that feature show up more clearly on the image.Ĩ. Now choose a point over an urban area and see that you will get a different spectral profile on your graph.įinally, choose a forested area and repeat the procedure.Īs you have probably figured out by now, the forest has a different spectral profile. A new screen will appear:Ĭlick on the cross button on this NEW Spectral Profile menu and then click somewhere in the water on the image.Ī line will appear on your graph that describes the spectral profile at given point. Now click on the graph button in the toolbar and a menu with appear:Ĭhoose Spectral from this menu and hit OK. Change The band combination back to 4,3,2. water, urban areas, forested areas, etc.) reflect different wavelengths. The purpose of the next part of the exercise is for you to see how ERDAS can help you see that different features (i.e. Forests might show up more clearly in a different band combination than soils.Ħ. For example, by knowing that soils shows up really well with a certain band combination you can use this combination to see them more clearly than you would with another combination of bands. You can play around with this band combination to give the image some really funky colors, but this feature is also useful. From the Viewer menu choose Raster -> Bands Combinations and a table will appear:Ĭhange the values on the right-hand side of the table to 5,2,1Īnd notice that the forested and grassy areas now appear green. Zoom back out to fit the image to the window and close the table that is now open to get rid of the cross-hairs. The LUT Value column assigns a number to each pixel based on a combination of red, green, and blue used to make the colors on your screen.ĥ. The File Pixel columns are the actual pixel values of your data. The columns assign to each pixel a value from 0 to 255 (called a DN number). ![]() Notice that the X and Y values in the table still change, but that the values in the File Pixel and LUT (Look Up Table) Value columns do not change. Move the cross-hairs again, but this time stay within one pixel. Zoom in on the image a few times so that you can see each individual pixel. As you do this, notice that the X and Y values in the table change. Use your pointer to move the cross-hairs by clicking once in the intersection of the two lines and dragging the center of the cross around. The following menu will appearĪnd white cross-hairs will appear on the image. Change back to the arrow button and click on. This part of the exercise is to illustrate the point that *** Clicking on the right mouse button gives you access to many of the functions in ERDAS*** So.if you cannot find a function in the menu or on the tool bar, try clicking once on the right mouse button.Ĥ. This command is analogous to the "Zoom to Theme Extent or Full Extent" buttons in ArcView. Click on the image with the right mouse button and choose " Fit Image to Window" from the menu that appears. On the toolbar inside the the Viewer window, click on the Zoom In button. Make sure that the file type is ".img".ģ. Open the "pnw98_bbg.img" file from the folder. In the Viewer window go to File -> Open -> Raster Layer. ![]() All available functions for ERDAS can be activated from the Menu Bar however, not all functions can be activated from the Viewer.Ģ. Open ERDAS IMAGINE from your desktop by going to Start -> Programs -> ERDAS IMAGINE When ERDAS opens, a Menu Bar running across the top of the screen and a Viewer window below the Menu Bar appear.
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