Introduction to Remote Sensing with Imagine8.4                       14 Nov 00

 

Instructor:      Doug R. Oetter             oetter@fsl.orst.edu          737-8417

 

Login and Materials

      This course was written for the Richardson 203 GIS laboratory computers, however, it can also be completed on your local computer by downloading the materials from the internet.

      To access the data via the internet, first download a grid-zipped tar file via ftp from ftp://ftp.fsl.orst.edu/pub/gisdata/help/course1.tar.gz.  Once you download the file to your local workspace, use these commands to uncompress and extract the data directory named "course1."  Inside this directory, you will find a Microsoft Word version of this document, which you may find easier to use than this on-line translation.

 

        NT:  Use WinZip to open and extract the archive, saving it to a local directory while preserving the file structure.  The directory you create will be your working directory for this tutorial.

        UNIX:  Use these commands to uncompress and extract the archive:

                gunzip course1.tar.gz

                tar xvf course1.tar

 

Introduction to Remote Sensing

      The science of remote sensing has developed to provide spatial information about features on the Earth's surface.  Since the advent of the Space Age, a wide variety of airborne and satellite sensing devices have been created to detect characteristics such as  surface temperature, atmospheric composition, vegetation structure, and the presence of precious minerals.  The various sensors now used by many public and private organizations are generally geared toward specific targets, and typically vary in spatial and spectral resolution to enhance important features.  In this workshop, we will use Landsat Thematic Mapper data, however the principles presented here could easily be adapted to a wide variety of other data sets.

      In most instances, remotely sensed data are stored as matrices, with the X and Y dimensions relating to a geographical projection of the Earth's surface and the pixel value representing some characteristic of that surface, such as reflectance in the near-infrared spectrum.  Multiple-band images are expressed as muti-dimensional matrices.   For display purposes, however, computer monitors can only display three bands (Red, Green, and Blue), so the user must choose how to display his image, even though all bands can be used in data manipulations.  In this regard, remote sensing datasets are quite similar to digital color photographs, and the software we use to process the imagery is comprable to packages such as Adobe Photoshop.

      For more information on remote sensing, students may wish to register for one of the courses on campus, particularly, GEO 463/563, or review one of the standard college texts, for example:

 

Avery, Thomas E.  1992.  Fundamentals of Remote Sensing and Airphoto Interpretation.  Macmillan.

Lillesand, Thomas M. and Ralph W. Kiefer.  1994.  Remote Sensing and Image Interpretation.  Wiley & Sons.

 

or one of the primary journals:


Canadian Journal of Remote Sensing

International Journal of Remote Sensing

Photogrammetric Engineering and Remote Sensing

Remote Sensing of Environment

 

or these web sites:

 

USGS EROS Data Center  <http://edcwww.cr.usgs.gov/>

SPOT Image  <http://www.spot.com/>

ASPRS Home Page  <http://www.asprs.org/>

Jing Huang's Face of the Earth  <http://www.fsl.orst.edu/~huang/rs_geoinfo.html>

U of Minnesota GIS/RS Information  <http://www.gis.umn.edu/rsgisinfo/rsgis.html>

U of Wisconsin ERSC  <http://www.ersc.wisc.edu/ersc/>

Goddard Space Flight Center's Remote Sensing Tutorial  <http://rst.gsfc.nasa.gov/>

Yahoo search for Remote Sensing  <http://dir.yahoo.com/Science/Earth_Sciences/Geology_and_Geophysics/Remote_Sensing/>

 

Starting Imagine

      To launch Imagine8.4, choose Start/Programs/GIS/Imagine on your NT computer.  You can exit Imagine at anytime with the Session/Exit command, or by shutting down your system.

      In the  UNIX environment, type "imagine84" at a terminal prompt.  In UNIX, Imagine runs in the background, which means that after it starts, you will be able to issue UNIX commands in the same terminal.  It is imperative that you exit Imagine before you log out, or otherwise it will continue to run in the background, which steals CPU memory from other users of your workstation and can deny someone else access to an Imagine floating license.

      The first thing that appears is the Imagine toolbar:

 

 

 

Most of the commands you will use in Imagine will be accessed by clicking on one of the tool buttons shown above.  But first, you should set up your user preferences,  using the dialog box under the Session/Preferences menu.  Your preferences control your Imagine work environment.  Many routine tasks, such as changing directories, can be avoided by setting your preferences in advance.  The Session/Preferences menu is divided into several modules:

      User Interface & Session-  here you will set your default data input and output directories.  You will quickly discover that Imagine requires a lot of mouse clicks to get to your desired file.  If you store your images in a central directory structure, and set that location as your default, you can speed up accessing your data.  Note that you should NOT use your N:\user or /users/user directory for storage of data files or your temporary file directory, because for public users, that directory resides on shared disk space, and you could easily overwrite the disk with an image output and freeze everyone else's essential processes.   You may wish to turn on the default preferences to delete session log on exit,  and delete history file, or otherwise Imagine will fill your home directory with log and history files.  At the bottom of this preference dialog, you may set your band to color defaults for typical image types.  Depending on the number of bands, Imagine will open an image in the Viewer with the default settings for AVHRR (5-band image), MSS (4-band image), SPOT (3-band image) or TM (6 or 7-band image).

 

      default data directory = C:\work\course1  (or your local workspace)

      output directory =   C:\work\course1   (or your local workspace)

      delete session log on exit = on

      delete history file on exit = on

      temporary file directory = (NT) $TEMP  or   (UNIX) /tmp

      TM red band default = 3

      TM green band default = 2

      TM blue band default = 1

           

      Viewer-  there are two settings that you will want to use to maximize the display properties of you Sun workstation monitor.  If you anticipate displaying a lot of vector files, you should set your default vector symbology file.  In addition, you may wish to turn 'off' the clear display button, or Imagine will always clear the viewer before opening another image.

 

      default symbology file = C:\work\course1\poly1.evs

      clear display = off

      (UNIX) display card depth = 24

      (UNIX) X-windows display visual = TrueColor

 

      Spatial Modeler-  the spatial modeler operates most of the image processing routines embedded in Imagine.  To save disk space, it is a good idea to use run-length data compression, which reduces file size for images which have long rows of similar data values (background).

 

      data compression = run length

 

      Vector-  you may wish to turn the node snap, arc snap, and weed tolerance off, because Imagine doesn't seem to calculate the best default values.

 

      use node snap distance = off

      use arc snap distance = off

      use weed tolerance value = off

 

      Image Files (General)-  To save disk space, you may wish to turn compute pyramid layers off.  Pyramid layers allow the rapid display of images in a viewer, however, they can add substantially to the image processing time and file size.  You can compute pyramid layers manually using the Image Info tool.

 

When you have finished personalizing your Imagine preferences, be sure to save the settings as User, and close the dialog.  Some of the preferences will not be changed until you restart Imagine.

     

      User Save

      File/Save to v8preference/user level

     

Image Display

      Images are displayed in a viewer.  Imagine opens one viewer when you launch the program.  You may open as many viewers as you like by clicking on the Viewer tool button.  Be aware, however, that the more viewers you have running, the slower your machine will operate.  It is best to close viewers that you are not using, and, when possible, stack your layers within a single viewer rather than have a separate viewer for each layer.

 

 

 

The viewer is operated with the selection of both pull-down menus and tool buttons.  You will find the tool buttons provide a quick way to access common tools, whereas the pull-down menus offer more processes and routines. 

To open an image in a viewer, use the Open File button  .  The ensuing dialog box allows you to select a file.  The default list is set to Imagine files (*.img) in your default data directory.  If you would rather open an ARC/Info vector coverage or grid, .TIF file, or many other data formats, change the file type at the bottom of the 'Files' frame.  If you need to move to another directory, use the 'Goto' button on the right for a quick way to move within the file system.  To re-open a file you had opened recently, use the 'Recent' button.  Once you've selected the file you want to view, click on the 'Raster Options' tab on the top to go to that frame.  Here you can select how you want to display the image- True Color is used for multiple-band images, and Pseudo Color and Gray Scale are used to display one-band images or a single band of a multiple-band image.  You then select which bands you want to display, and whether to clear the display or fit the image to the existing frame.

 

      Open File button

            directory = C:\work\course1\

            file type = IMAGINE Image (*.img)

            filename = tm95_4529_andrews.img

            layers to colors = 3,2,1

           

      To close the top layer in a viewer, you can use the Close Top Layer button  .  To close all layers in a viewer, use the Clear Viewer button  .

 

      Use the Image Info button    to view the information about an image.  A lot of very important details about an image are displayed and edited in this dialog.  Image info tells you how many layers an image has, whether it's a continuous (pixel values represent interval level data) or thematic (pixel values represent classes) image, the width and height (in pixels), whether the image is compressed, and whether pyramid layers exist.  In addition, Image Info displays the map coordinates, pixel size, and projection information.  Many of these settings can be edited with the Edit menu.  Use Edit/Compute Pyramid Layers to add pyramid layers to an image so that it will display faster.  Frequently, you will need to Edit/Change Map Model to shift the upper left X and Y coordinates of an image so that it will match other images in your data library.  Or you may need to Edit/Change Projection to install a datum type if it was previously "undefined."  Use Edit/Compute Statistics to recalculate the statistics of an image.  You may want to Ignore Value = 0, so that the background doesn't influence the calculation of the display lookup table (if the display of an image ever appears very dark, check to see if the background value was ignored in the statistics).  And for some operations, you will need to recalculate the statistics with a skip factor of 1,1, which means that every pixel is sampled to create the statistics.  You can View/Histogram to see the distribution of pixel values band by band, and once you set File/Print Options, you can File/Print the statistics and histogram at your local postscript printer.

      You can save the top layer in a viewer with the Save Top Layer button  .

      Use the Zoom In    and Zoom Out    buttons to adjust the display scale of the image.

      The Measure Tool button    opens a dialog which allows you to digitize lines and polygons for measurement purposes.

      The Inquire Cursor button    lets you examine a single pixel in the image.  You can display its location in map projection, file, or latitude/longitude coordinates, and see the pixel values for each band.  The bands which are currently being displayed are shown with their appropriate colors next to them. 

      The Tools button    opens a separate toolbar for the top layer (AOI, Raster, Vector, or Annotation).  These toolbars speed your access to common procedures which are also available from pull-down menus.

      The Zoom In Lens    and Zoom Out Lens    buttons allow you to select the center point of the zoom area, or define the outer edge of a zoom area.

      The Hand button    allows you to move the image by clicking and dragging the hand icon.  Double-clicking activates virtual roaming (if it is set in the View menu).

     

      Under the Utility menu, you will find the options Inquire Color and Inquire Shape, which let you change the color and shape of your inquire cursor.  This can be particularly useful when your image is washed out and the cursor is difficult to see against the light background.

 

      When you have explored the above tools, open a second viewer with the same image displayed in bands 4,3,2.  Open the Arrange Layers tool, which shows you which layers you have in a viewer and their display order.  Open the Scale Tool, and experiment with adjusting the representative fraction for the display scale.  Next, use the Link Viewer option to link the two viewers and display the same geographic areas in different band combinations.

 

      Viewer button

      Open File button

            filename = tm95_4529_andrews.img

            layers to colors = 4,3,2

 

In Viewer #2:

 

      View/Arrange Layers

      View/Scale/Scale Tool

      View/Link-Unlink Viewers/Geographical (click in viewer 1)

 

      Open the Inquire Cursor to track the same pixels in the two viewers.  Notice the difference in band display.  You can change the display band combination of an image without reopening it.  Change the display band combination of  Viewer #2 from 4,3,2 to 5,4,3 with the Raster menu.  Note that you cannot scroll or zoom in the viewer until you have closed the dialog.  Experiment with other combinations such as 7,5,3 or 4,5,3.

 

      Raster/Band Combinations  (set to 5,4,3)

 

      Many commands in Imagine can be accessed in multiple places.  For instance, you can also open the Band Combinations dialog by using a right-hold on the layer icon in the Arrange Layers box.  Do a right-hold inside the viewer for the Quick View Menu, and fit the image to the window.

      Quick View Menu (Right-hold inside viewer)

            Fit Image to Window

 

You should now Close Viewer #2.       

      File/Close (inside Viewer #2).

 

Areas of Interest (AOIs)

 

      Areas of Interest are the line and polygon format files that IMAGINE uses for clipping and subsetting images and for creating signatures to be used in a supervised classification.  You can generate and edit AOI files with the AOI Menu and Toolbar.

Text Box:        First, create an AOI by opening a new file.  Then open up the toolbar by selecting AOI/Tools... or clicking on the Tools    button, and select the Polygon Tool by clicking on the Draw Polygon    button.

 

      File/New/AOI Layer

            Open AOI/Tools...

            Digitize Polygon

You can select an AOI with the Selection Arrow  , and then Reshape    or Delete    it using the appropriate toolbar buttons.  The Lock    button keeps one tool locked and ready.

      Use the Polygon Tool to digitize a rough boundary of the H. J. Andrews Experimental Forest (the triangular-shaped, heavily forested watershed in the center of the image).  Double-click to place the last point and close the polygon (UNIX: middle button).  Edit the polygon by first selecting it and the resizing or moving the selection box.  Using Reshape, you can relocate individual points, or even add points by moving the cursor to the polygon boundary and clicking the middle mouse button. You can delete points using this same procedure with the shift key depressed; just move the cursor to the point you want to remove and use Shift/middle mouse button. When you are finished editing the polygon, click in the viewer, but outside of the polygon to deselect the polygon.

      Save your AOI file to a name with File/Save AOI Layer As. Enter a name and click OK.


            File/Save/AOI Layer As

            "boundary.aoi"

            OK

 

Copy AOI to Vector

      There may be times when you want share AOI files with other people using ARC/Info.

It is usually easy to convert AOIs to ARC/Info vector or polygon files.

 

1.  Start by displaying an AOI file in the Viewer. In this case, you should still have the AOI file you just created on display.

 

2.  Create a new Vector layer by selecting File/New/Vector Layer from the Viewer menu bar. Enter "study" as the file name, click OK, and choose single precision.


3.  Click on the AOI "boundary.aoi" that you created. If it is selected, you should see a selection box around the polygon.

 

4.  From the Viewer menu bar select Vector/Copy Selection to Vector...

 

5.  Open the Arrange Layers dialog by selecting View/Arrange Layers from the Viewer menu. Move your cursor to the AOI layer, right-hold and choose Delete Layer.  Click Apply at the bottom (you do not need to save the AOI layer- it was not edited, but Imagine asks you this every time anyway).   Again in Arrange Layers, move your cursor to Vector: study, right-hold, and choose Save Layer.

 

Text Box:  6.  After you create a new vector layer you may want to create and edit polygon attributes.  To do this, select Vector/Attributes from the Viewer menu.  The Attributes dialog, also called an Attribute Editor,  is opened with the title Attributes for .../course1/study dialog box .  Select View/Polygon Attributes.  Select Edit/Create Attributes.  This should add area, perimeter, study#, and study-id columns.

 

7.  Now select Edit/Column Attributes in the Attribute Editor. Click on New and add the following information. When you are finished click OK.

 

      Title = "SITE"

      Type = String

      Max Width = 10

      Display Width = 12

 

8.  Select the Polygon Label point in your viewer (a small dot inside your polygon). This will highlight the record in the Attribute Table.  Enter "HJ Andrews" in the newly added column

 

9.  Close the Attribute Editor.  Save the vector file with the command File/Save Top Layer from the Viewer menu.

 

10.  Delete "study" by clicking the Delete Top Layer button.

 

11.  Build polygon topology for study by selecting Vector/Build Vector Layer Topology... from the IMAGINE Icon Panel.  The input coverage is "study", and the feature is polygon.

 

12.  If you re-load "study" and open the vector attribute editor, you will find that it consists of two polygons, the universal (background) polygon, and the polygon you drew around the HJ Andrews. 

 

13.  To re-edit the polygon or attributes, you must first choose Vector/Enable Editing.  Screen digitizing arcs and points in Imagine works quite well, using the same tools as with AOI digitizing.  To snap nodes and arcs, you will need to experiment with Vector/Options, because Imagine calculates default options which usually are not what you would want.

 

14.  After you've examined and edited the built version of "study", clear your viewer with the Clear Viewer button.

 

      Many of these vector functions can also be performed using the Vector Toolbar shown above.  As you get more comfortable with Imagine, you will find that it helps to have several ways to perform the same task.  The Vector Toolbar has several advanced features that we will not discuss in this class, however it shouldn't take long to get familiar with them.

 

Overlaying Vector Files

      More than one vector coverage can be brought into a viewer and used for reference or in Map Compositions. Each coverage can have its own display properties as long as they are saved separately in symbology (*.evs) files. These files are necessary if the vector coverages are to be used in Map Compostions. Examine now some of the possible vector properties that you can use. Open the following vector files with their associated *.evs files.

 

      File/Open/Vector "hja_bnd"

         Vector Options tab

            Use Symbology =  on

            Set ...:  /poly1.evs

      Open slides w/ point1.evs

      Open raingages w/ point2.evs

      Open hydro w/ hydro.evs

      Open roads w/ roads.evs

      Open mushroom w/ poly2.evs

      Open deposit w/ deposit.evs

 

      Vector/Show Symbology from Arrange Layers dialog

 

      Examine roads.evs and deposit.evs.  These two symbology files are examples of attribute-based symbology.  The appearance of the polygon depends upon the value of one of its attributes.  In the case of "roads", the thickness of the line depends on the size of the road (attribute CODE), and for "deposit" the coloration of the polygons comes from the stability code.  You can view the metadata file for "deposit" (deposit.doc) in a text editor.  You can check this if you want by selecting certain polygons based on a selection criterium in the Attribute Editor.

 

      Open Attributes for "deposit" by right-holding in the View Layers dialog

            Right-hold in the far-left column beneath Record for the Row Selection menu

            Select Criteria

                  Select Columns = STABILITY

                  Select Compares = "=="

                  Select Numberpad = 1

 

This will highlight all the polygons in the Attribute Editor and the Viewer which have a high hazard of earthflow susceptibility (please refer to the documentation file for the coverage "deposit.doc").  If you wanted to, at this point, you could copy the selected polygons to an AOI or new vector coverage which you could use to subset an image or coverage.

 

Open the raster image  "tm95_4529_andrews.img" as 3,2,1 using the Open Layer button with the Clear Display option.

 

Subsetting Images

 

      This is a way of reducing the extent of an image to include just the area that is of interest. If you have a small study area and a much larger image, you will save on processing time and disk space if you subset the image before classifying it. Two methods are described below.

 

Method 1: AOI (maintains original image extent, but eliminates unwanted image data)

 

1. With Image "tm95_4529_andrews.img" in a viewer, open a Vector file to display on top of it. From the Viewer menu, select File/Open/Vector and select the File "hja_bnd," click on Vector Options and make sure the use symbology file button is on and the the file poly1.evs is selected.

 

2. Once the polygon is displayed, select it by clicking on it. This should change the orange color to yellow. IMAGINE can display and manipulate ARC/Info vector files, but uses AOIs for more functions.  To convert the file to a format that Imagine can use, go to the Viewer menu and Click on AOI/Copy Selection to AOI.  To save this new file, go to View Menu Bar, File/Save/AOI Layer As and type in the name bnd.aoi.

 

3. You now have a file you can use to clip or subset the image with.  On the IMAGINE Icon Panel, click on Data Prep/Subset Image. Input the following  information:

 

      input file = tm95_4529_andrews.img

      output file = tm95_4529_andrews_6b_cut.img

      ignore zero in output stats = on

      select layers = 1:5,7 (will select bands 1,2,3,4,5 and 7)

 

At the bottom of the Subset Dialog Box, click on AOI, select file, and enter the newly created AOI file name "bnd.aoi."  Click OK on the Choose AOI Dialog Box. Click OK in the Subset Dialog Box.  While Imagine is working on your subset process you have the option of starting on Method 2, or doing what most of us would do, and going for a coffee break!

 

Method 2: Inquire Box (decreases image extent and elimnates unwanted image data, but does not clip to an irregular boundary).

 

1.  With the Image "tm95_4529_andrews.img" displayed in a Viewer (File/Open/Raster), start the Inquire Box (Utility/Inquire Box from the Viewer menu bar or Quick View Menu/Inquire Box in the viewer). Grab and drag corners of the box to fit the area you are interested in, in this case the HJ Andrews. You will notice that the coordinates will change in the small box.

 

2. Now you can use this coordinate information to identify the image area of interest in the Subset dialog box. On the IMAGINE Icon Panel, click on Data Prep/Subset Image. Input the information listed below:

 

      Input File = tm95_4529_andrews.img

      Output File = (leave blank)

      Click From Inquire Box to use the coordinates you identified with the Inquire Box

            (you may wish to round the subset coordinates at this point)

      Ignore zero in output stats = on

      Select Layers = 1:5,7

      CANCEL (since you have already subset the image using Method 1)

 

Now Clear Viewer and Load your subset image "tm95_4529_andrews_6b_cut.img" (3,2,1)

 

Unsupervised Classification

 

      Classification is the process of grouping pixels in a image into distinct classes based on the raw image bands. Once the groups are created, the image analyst (you or your grad student) assigns class descriptions/names based on their location in the image. This process is labeled as 'unsupervised' because the computer uses a statistical routine to develop classes based on image pixel values and is independent of any pre-existing information from the image processing analyst.

 

      The first step in this process is to run the statistical algorithm which will break the image into unique classes. For this exercise, you will just fill in program parameters but you will not run the process. The classified file has already been created, to save time.

 

Data Prep/Unsupervised Classification...

Input File = tm95_4529_andrews_6b_cut.img

Output = <leave blank>

Number of Classes = 15

Maximum Iterations = 10

Convergence Threshold = 0.990

Skip Factors = 1,1

Classify zeros = off

 

The main parameter to note for now is that we will generate 15 classes. This means the image will be broken into 15 groups.  The process will run for 10 iterations or until it reaches a convergence of 0.99.  It will examine every pixel in the image (skip factor), and ignore pixels with values of 0.

 

Click on the Cancel button and we will continue the exercise with the file that has already been created for you.     

 

Evaluating Newly Created Classes - Viewing Classified Thematic file over Raw Image

     

      One of the common ways to decide what the newly generated classes represent is to view the new file over the original image.

 

1.  Start by bringing the subsetted image, "tm95_4529_andrews_6b_cut.img", into the viewer if it is not already on display.  Go to the viewer menu bar, select File/Open/Raster and select "tm95_4529_andrews_6b_cut.img". Click OK.

 

2.  Next, bring the classified thematic file in as a second file on top of the raw image.  Go to the viewer menu bar, select File/Open/Raster and select "andrews_cut_unsup_15cl.img". Make sure the Clear Display button is clicked off.  Now you have two files on display in the viewer. The thematic classified file is on top, so it is the active layer. It looks like a gray scale version of the original image. In the next part of the exercise, you will view each class separately and assign a class name/description to it.

 

3.  In the Viewer tool bar, open Image Info. Note the layer type, statistics, and histogram

 

4.  Go to the Viewer menu bar, select Raster/Attributes.  Once the editor comes up, note the new categories. There are columns for class name, color, the RGB color values, opacity (transparancy value), and pixel count. This is where you can enter a description of the land cover type.  The layout of the Raster Attribute Editor has been set for you using Edit/Column Attributes.  Now change each class opacity to 0 so you can see the raw TM image below:

 

      Right-hold in the Row headings and Select All

      Left-click the Opacity column heading

      Right-hold the Opacity column heading and select Formula

      Left-click in the Formula box and type "0"

      Click Apply

 

Once all class opacity is set to 0, you will go back to each class, one by one, change its opacity to 1, make it a bright color and decide what it is.

 

5.  Go back to the Row column and right-hold to chose Select None.  Put your cursor over the Color Cell for Class 1. Hold down the right mouse button and a Color Menu will appear. Select RED and change the Opacity to "1". Class 1 will now show up as red on top of the raw TM image. 

 

6.  The next step is to flash the class selection on and off so that you can see what part of the image is beneath the class and determine what land cover type the class represents in the image.  Go to the Viewer menu bar and select Utility/Flicker. Click on the Manual Flicker button and the red colored class will turn on and off each time you click. After you determine what it represents in the image, you can click in the Class Name Cell and enter a description.  For this exercise, to keep things simple we will assign one of four class names:

 

      Disturbed (new clear cuts/roads/bare ground)              Yellow

      Old Forest                                                                  Dark Green

      Mature Forest                                                            Green

      Young Forest                                                              Cyan

 

7.  Once you have decided what Class 1 is, change its color according to the legend above (use a right-hold on the color cell for color choices), and enter a code in Class Names.

 

8.  Go to the Color Cell for Class 2 and change its color to Red with opacity = 1. Use Utility/Flicker to turn the class on and off.  Once you have assigned one of the descriptions above to each class, you can recode the file to simplify it for making maps and further analyses.

 

Thematic Image Recode

 

      Go to the IMAGINE Icon Panel and Select Interpreter/GIS Analysis/Recode.

 

Input File = andrews_cut_unsup_15cl.img

Setup Recode (set New Value for all classes)

Disturbed         >>     1

Old Forest        >>     2

Mature Forest >>     3

Young Forest   >>     4

Output File = andrews_cut_unsup_4cl.img

Data Type/Output = 4 bit

Ignore Zero = on

 

         Here "Value" represents the original Class Number (1-15), and New Value represents what its recoded value will be (1 - 4). You can type each value in individually or select all rows that will have value 1 and use the Change Selected Rows button.  When you have finished entering the new values click OK on the Thematic Recode dialog box and click OK on the Recode dialog box.  Because this is a thematic image, which requires much less disk space than a multiple-band continuous image, you may not have time for a full-out coffee break during this process.

      Next open a second viewer (click on the Viewer button from the IMAGINE Icon Panel), and display the newly recoded file "andrews_cut_unsup_4cl.img."

      Open the Raster Attribute editor of this file by selecting Raster/Attributes... from the Viewer menu bar. Notice that the attribute information you entered for  "andrews_cut_unsup_15cl.img" is gone.  Recode doesn't keep class attributes because they are merged; it is very important to KEEP A RECORD of your recoding decisions!  Enter Class Names and assign Colors to each class.  Add an area column by selecting Edit/Add Area Column from the Raster Attribute Editor menu bar.  Select hectares, acres or square miles, and click OK.  Save your changes with File/Save.

      To export your spatial information to a text file, Select All row headings and the Class Name and Area columns, then right-hold in the column heading and select Export....  The Export Column Data dialog appears, where you will specify the export filename for the column information.  This data file (*.dat) can be imported to spreadsheets and graphics programs.  You might also investigate the text report created with Edit/Report.

 

Map Making in Imagine

 

      The Imagine map making tool is a very simple way to generate high-quality map products which can be output directly to the color printers or plotters in the complex.  While we will not have time in this exercise to go into detail about Map Composer, you may wish to make a simple map using these commands:

 

1.  Set up the raster images and vector layers in a viewer exactly the way you want to display them in your map.  Use the Arrange Layers dialog to put line vectors on top of raster images.  Each vector layer must have a saved symbology ( *.evs) file.

 

Text Box:  2.  Click on the Composer button on the Imagine toolbar.

     

3.  Select New Map Composition and set these map parameters:

            Name = "HJA_letter"

            Width = "10"

            Height = "8"

     

4.  Start by sizing your map viewer window and Fit Map to Window.

 

5.  Use the Input Frame    tool to insert the contents of the viewer into the map.

     

6.  Add a title using the Text    tool (set the text size with the Annotation/Styles dialog).

     

7.  Add a scale bar using the Scale Bar    tool.

     

8.  Add a legend using the Legend    tool.  The legend tool will only work for the active, or top, data layer, so use Arrange Layers to move the thematic layer temporarily to the top.

     

9.  Add a north arrow

      Set the Annotation/Styles for point symbology to a north arrow option, then Insert Point    where you want the north arrow.

     

10.  File/Save/Map Composition.

     

11.  File/Print to "r207clj8500.for.orst.edu" (or other printer).

           

For more:

 

            This concludes our introductory workshop.  For more help with ERDAS Imagine, please refer to the ERDAS manuals (ask at the helpdesk or look in FSL345) or the Forest Science Research Network helpdesk web page <http://www.fsl.orst.edu/helpdesk/gis/>.  You should also become familiar with the Adobe Acrobat files that are stored within the software at M:\Win32\IMAG84\help\hardcopy\ (NT) or  /tools/erdas83/840/help/hardcopy/ (UNIX).