exercise 1 subsetting an image - portland state...

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Exercise 1 Subsetting an Image

Review viewer icon panel below (with instructor).

Obtain the file

1. Click open file icon.

2. Navigate to C:\Land_cover_tutorial to open file: westga89_georef.img.

3. Right click on the image and select “Fit image to window”.

i. This “full” TM image is 185 km wide/170 km high. Atlanta is in the NE

quadrant.

Review viewer menu bar (with instructor).

In Viewer menu bar

1. Click AOI; Select Tools

2. In AOI tool pallet; Select “create rectangle” button (1st row, 3rd

column).

3. Within viewer, click and drag to select a subset of the image.

Illustration I:

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(NOTE: Your selection should appear exactly as in Illustration I above. If you click outside

the AOI selection, it will become deactivated and you cannot proceed until you click again inside

the selection. An active AOI selection is represented by a solid white line with black squares

around the perimeter and one in the center.

On main icon panel

1. click Interpreter icon

2. Click Utilities.

3. Click Subset.

(Your screen should resemble Illustration II below).

Illustration II

1. Next to Input file field, click open file icon.

2. Navigate to C:\Land_cover_tutorial\westga89_georef.img.

3. Left click on this file.

4. Click OK.

5. Next to Output file field, click open file icon.

6. Navigate to C:\Land_cover_tutorial.

7. Type file name “subset_1”,

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8. Click okay twice.

9. Click “AOI” button (bottom center of subset screen).

10. Select viewer button.

11. Click okay.

12. Click okay again to initiate subset modeler

13. Click okay again once modeler is complete.

14. Close Image Interpreter, Utilities, and AOI windows.

15. Open new viewer by clicking “viewer” icon on main panel.

16. Click open layer icon, then click “recent” button and select

“C:\Land_cover_tutorial/subset_1.img”, then click okay.

17. Click okay again in “Select Layer to Add” window to display subset in viewer #2.

If you selected the same area as seen above on the image shown in this exercise, you should have a subset

showing Hartsfield airport.

1. Use the “+” and “-“ magnifying tools to zoom in and zoom out of the scene.

2. By zooming in just a couple of times, you can see the individual pixels that make up the scene. This

is TM imagery, so the pixels each represent the reflectance from a 30X30 meter-square ground

surface.

In the viewer #2 menu bar

1. Click “raster”

2. Select “band combinations”.

3. Change the layers to RGB = 5,4,2

4. Click apply.

5. Try a natural-color image

a. set the layers to RGB = 3,2,1

b. Click apply

c. Reset to 5,4,2 and close.

In the viewer #2 menu bar

1. Click on the “Roam/rotate image” button (the hand icon)

2. Roam/pan around the image.

3. Right click

4. Select “fit image to window”

5. Close viewer #2.

Create another subset or subsets of your choice from the full image, and save to the workshop folder.

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Exercise 2 Unsupervised Classification

Click open layer icon

1. Navigate to C:\Land_cover_tutorial to add file “carrollton89sub.img”

2. Caution: Don’t click okay yet

3. Select the “raster options” tab

4. Check the “clear display” box

5. Now Click okay.

6. Right click and select “Fit image to window”.

Click “Classifier” from main icon panel, and then select “unsupervised classification”. In the

Unsupervised Classification panel, next to Input raster file field

1. Click open file icon

2. Navigate the workshop folder

3. Select “carrollton89sub.img”

4. Click okay.

Illustration I:

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In the “Output Cluster layer” box

1. Click the open file icon

2. Enter file name “carrollton89unsup”

3. Click enter twice.

In the Output Signature Set


2. Enter file name “carrollton89unsup”

3. Click enter twice.

4. Under “clustering options” change # of classes to “20”. Click “initializing options”, select

“principal axis”, and then close small panel (NOT “unsupervised classification” panel).

Within viewer menu bar

1. Click raster

2. Select “Band Combinations”

3. display RGB = 5,4,2. If necessary, change layer 4 to layer 5, layer 3 to layer 4

4. Click apply and okay.

Illustration II:

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Return to Unsupervised Classification panel

1. Under clustering options click Color Scheme Option

2. Select “Approximate true color”

3. Reset red, green, blue to 5,4,2 respectively

4. Close.

In the “processing options”

1. Set “maximum iterations” to 10

2. Set “convergence threshold” to 0.95

3. Click okay.

The Isodata Classification Job Status Meter should appear.

1. Click okay when the job state is done

2. Close classification window.

Open new viewer by clicking “Viewer” icon on the main panel.


2. Click “recent”

3. Select “C:\Land_cover_tutorial\carrollton89unsup.img” (note .img NOT .sig)

4. Click okay twice

5. Right click and select “Fit image to window”.

Illustration III:

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In the “Viewer” menu bar

1. click “view”; Select “Tile Viewers”.

2. Click “view” again

3. Select “link/unlink viewers > geographical” (Click anywhere in opposite viewer to activate.)

In the left viewer

1. click on the magnifier (+) tool icon

2. Click once in the center.

In the right viewer, the area within the box corresponds to the area in the left viewer.

1. Click on the magnifier tool (+) icon; Click once in the center of the outlined box.

2. Click the hand icon in the left Viewer

3. Click and drag to pan both images simultaneously.

4. Right click to fit image to window in both viewers.

In the Unsupervised Viewer

1. click “Raster”

2. Select “Attributes” to allow renaming of preliminary class names. CLASS NAMES: BARE

GROUND, DEVELOPED, GRASS, TREES, WATER, WETLANDS.

In the Raster Attributes Editor

1. Click the Column Properties icon to reveal Column Properties dialogue.

Illustration IV:

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We will now duplicate the color column in the raster attributes editor as a back up.

2. Click the “New” button

3. Check the “Editable” checkbox next to the Title field

4. Change “column 8” to Color 2” as the new title.

5. Select “Color” in the Type field

Rearrange the order so that column titles “Class Names, Color, and Color 2” are consecutive (at the top)

1. select the column title

2. Click the “up” or “down” buttons to relocate.

Click “Class Names” from the top of list.

1. Change the “display width” to 10.

2. Click okay.

In the raster attribute editor

1. Copy the original colors into the new column (color 2)

a. Click the column name Color

b. Click the copy icon

c. Click column name color 2

d. Click the paste icon.

We will edit the color column; keeping the copy for backup in the highly unlikely event we make a

mistake…..

10. Click and drag the right corner of the Attribute table

11. Resize to show just class names and color patches.

12. Click on “1” in the “Row” column

13. Click the color patch for “class 1”

14. Select “gold” to allow this class to stand out.

15. Determine the name of this class. (water, bare ground, etc.).

Remember that the image in viewer #1 is the original, and the image in viewer #2 is the classification. Refer

to the original image for guidance on the land cover types. You can minimize the editor, zoom in and roam

to determine the land cover type.

1. Click the gold color patch again

2. Replace with blue representing water.

3. Replace the text “class 1” with appropriate land cover name.

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Illustration V

4. Click on “2” in the “Row” column

5. Click the color patch for “Class 2”

6. Select “gold”

7. Determine the name of this class. (water, bare ground, etc.).

8. Click the gold color patch again

9. Replace with dark green representing trees.

10. Enter “trees” in the class name column.

11. Repeat for all classes that are “greenish” in the original color column (Classes

3,5,6,7,9,12,15,17).

12. Discriminate between grass and trees.

13. Choose green as the color patch for grass.

14. Remember that you have to select the row number in the row column before you select the color

patch!

15. Evaluate classes 16 and 18, using the same procedure.

Notice that although the original color in the image and classifications were not “greenish”, there is a

clear association with the “grass” classifications. How would these two classes be renamed? Place the

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cursor close to UTM location 676811, 3715472, zoom in one click, and observe in both Viewers. What

type of human development is this? Fore is your clue. Change color patch to appropriate color and

rename. Fit image to window in both viewers.

16. Select the color patch for class 11

17. Change to gold. This represents commercial/industrial development.

18. Change color patch to red and rename field “developed”.

19. Evaluate and rename class 13.

20. For class 14, observe UTM coordinates 674642, 3722518 (far upper left corner of image) in the

original image. This dark pink signature represents bare ground.

21. Change color patch to white and rename.

22. Evaluate and rename class 19. What signature is associated with this class?


24. Turn class 8 pink. Based on the association with other signatures, is this class natural or

developed land cover? Do we need to establish a 7th class to accommodate non-commercial

development such as residential land cover? Name this class “residential”.


26. What about class four? Click on row 4 in the Row column and change the color patch to black.

Zoom in and observe the cluster of lakes in the center of the image. (UTM coordinates: 677846,

3718847). Zoom out and observe additional drainage patterns north of Lake Carrollton at UTM

679834, 3719889. Rename appropriately.

27. Change the bare ground color patches to orange.

28. Save and Close both viewers.

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Exercise 3 Combining or Recoding Classes

Open “carrollton89unsup.img” in an empty viewer

1. From the “Viewer” menu

a. Click “Raster”

b. Select “Attributes”.

c. Click “Raster”

d. Select “Recode”.

We will recode the twenty classes into seven classes, # 1 = water (blue); # 2 = forest (dark green); # 3

=wetlands (black); # 4 = residential (pink); # 5 = developed (red), # 6 = bare ground (orange); # 7 =

grass (green).

1. Click row 1 in the recoding dialogue; note the new value shall remain the same as the old value

because there is only one original water class.

2. Click row 2, while holding shift key select all forest classes: 2,3,5,6,7,9,12.

Illustration I:

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3. Change the “New Value” field below table to “2

4. Click “Change Selected Rows” (all preliminary forest classes are now recoded to class “2”) .

a. Right click in the Row column and “select none”.

5. Click Row “4”

a. Change “New Value” field to “3”

b. Click change selected rows.

c. Right click and select “select none”.

6. Click rows “8” and “10” (holding shift key)

a. Change “New Value” to “4”.

b. Right click and select “select none”.

7. Click Rows “11”, “13”, “20”



8. Click Rows “14”, “19”



9. Click Rows “15”, “16” “17” “18”



10. Once complete, click “Apply” and close.

11. Close Raster Attribute Editor by selecting “File> Close”.

The image in the viewer now DOES NOT look like we wanted it to! DON’T PANIC – YOU DID IT ALL

RIGHT (PROBABLY). You SHOULD only have three colors, but we will fix it below.

In the viewer,

1. Save recoded file as a new image by selecting “File>save> top layer as…”

2. In output file name enter “carrollton_89_recode”

3. Click okay.

Open “carrollton_89_recode”

click “Raster>Attribute”. Here we rename and color each class correctly. # 1 = water (blue); # 2 =

forest (dark green); # 3 =wetlands (black); # 4 = residential (pink); # 5 = developed (red), # 6 =

bare ground (orange); # 7 = grass (green).

1. Click on the column properties icon

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2. Move “class names” until it is underneath “value” to the top

3. Change the column width to 10.

4. Move “color” beneath “class names”.

5. Click okay.

6. Rename classes, and change color patches to match those given above.

12. Once finished, click “save changes to file icon”

13. Close Raster Attribute Editor.

14. From viewer, click “save top layer” icon.

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Exercise 4 Supervised Classification

Click open layer icon

1. Navigate to C:\Land_cover_tutorial to add file “carrollton99sub.img”.

2. Right click

3. Select “Fit image to window”.

4. Within viewer menu bar, click “raster”

5. Select “Band Combinations.”

6. If necessary, change to R:5, G:4, B:2

7. Click okay.

YOU ARE NOW GOING TO PICK “TRAINING AREAS” FOR SPECIFIC LANDCOVER CLASSES.

We have chosen specific pixels to do this, because we know that they will work. If you use another

pixel, you will get off track. At this point the instructions may get tedious, and you may be inclined

to explore. Good idea – but be patient for now and keep following the instructions so that this will

work for you the first time.

Choose a “training area” for the class “water”. Begin with the lakes in the center of the scene.

a. Within viewer menu bar, click the “inquire cursor tool” (the + sign).

b. Type in exact UTM coordinates 677846, 3718847 in the X and Y fields in the panel that

opens with this tool.

c. Use the zoom tool to enlarge the area, by clicking three times on the lakes with the positive

zoom tool at UTM coordinates: above)

d. Click the arrow tool in the viewer menu bar

e. Move the inquire cursor into the center of the water area.

f. Minimize the inquire cursor dialog box

g. DO NOT CLOSE IT!

Select “Classifier” from the main icon panel.

i. Choose “Signature Editor.”

ii. Close the “Classification” menu.

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Illustration I:

Within viewer menu bar

1. Click “AOI”

2. Select “tools.” (You will only need these tools if you make a mistake later in the exercise…)

3. Click “AOI”

4. Select “Seed Properties”. This opens the “Region Growing Properties” panel.

5. Change “neighborhood” to “eight neighborhood mode”.

6. Click on the area

a. Set area to “1000” pixels.

b. Set “Spectral Euclidian Distance” (SED) to 5.00.

7. Click “Grow at Inquire”.

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Illustration II:

Reset “SED” to 10.00

1. Click “redo” NOT “GROW AT INQUIRE!!!” If you accidentally click “grow at inquire”

again, use the little scissors tool on the “AOI tool” icon panel to remove the second AOI. Click

on the scissors icon, then click in the viewer to reselect your original AOI, then click redo with

your new SED.

2. Try resetting the distance until the entire lake is included in your training area. “Spectral

Euclidian Distance” settings over 20 are not recommended!

3. Return the setting to 10.00.

In the signature editor

1. Click on the “Create new signature from AOI” tool (third from the left). This adds your new

water signature.

2. Click the name Class 1 and type in water.

3. Click the color patch and select blue.

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4. Scroll to the right in the signature editor until you see the “Count” (column 9). This tells you

how many pixels are in your training area. Huge training areas are not necessary. Training

areas smaller than 7 pixels are ignored in the classification process. Check this “count”

after you create each training area in this exercise – it MUST be more than 7!!! Some

landcover classes may end up with <7 pixels, if you are being too conservative. This will

means that the signatures you picked are not used in the classification!

5. Fit image to window.

Illustration III

15. Maximize the inquire cursor panel by clicking “Viewer #1” bar at the bottom of your screen.

16. Type in UTM X = 681362, Y = 3714482.

17. Zoom in to the lower right portion of the image by clicking with the positive zoom tool twice at

the cursor location.

18. Select the arrow tool in the viewer menu bar

19. Grab the inquire cursor

20. Move the cursor to the DARK GREEN rectangular area at UTM 681290,3714772.

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21. Minimize the inquire cursor panel.

Go to the “region growing properties” dialog box

1. Reset the SED to 5.

2. Click “Grow at Inquire”. At least 7 pixels are needed for an adequate training area.

3. Set the SED 10

4. Click “redo”.

In the “Signature Editor”

1. Click the “Create new signature from AOI” tool.

2. Change the signature name to “deciduous trees”

3. Change the color patch to dark green.

4. Move the Inquire Cursor to the southeast, to UTM 681514, 3714553, by typing these X,Y values

into the inquire cursor panel.

5. Go to the “region growing properties” dialog box

a. Reset the SED to 5.

b. Click “Grow at Inquire”.

c. Set the SED to 10.

In the “Signature Editor”

1. Click the “Create new signature from AOI” tool.

2. Change the signature name to “evergreen trees”

3. Change the color patch to turquoise.

Establish a “grass” signature at UTM 676390,3716810. (Remember not to exceed an SED of 20).

1. Click Add signature

2. Rename signature to “grass”

3. Change color patch to green. Remembering that grass had several distinct signatures in the

unsupervised classification, establish another “grass” signature at UTM 675165, 3718475.


5. Rename signature to “grass2”

6. Change color patch to green.

Establish a “wetlands” signature at UTM 673633, 3716077. Keep raising the SED until you have at least

7 pixels in the count.


2. Rename to “wetlands”

3. Change color patch to black.

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Establish a “bare ground” signature at UTM 676933, 3721596.


2. Rename to “bare ground”

3. Change color patch to orange.

Establish a “roads” signature at UTM 681790, 3718211.


2. Rename to “roads”

3. Change color patch to red.

Establish a “commercial/industrial” signature at UTM 679286, 3715689, using the “create rectangle

AOI” tool from the AOI toolbar (top row, third column).

1. Drag a rectangle ~ 8 X 8 pixels in size. This rectangle includes both roofs and parking lots,

which establish the signature.


3. Rename to “commercial/industrial”

4. Change color patch to yellow.

Establish a “residential” signature at UTM 680352, 3718748. Keep the “Distance” small, or trees in

the residential area will overwhelm the signature. This is a problem in older residential areas

because trees obscure the residential signature. Use the minimum SED necessary to get > 7 pixels.


2. Rename to “residential”

3. Change color patch to pink.

Now is the time to check your pixel “Counts” to make sure they are ALL > 8. Save signature

editor to ATE workshop folder as “Carrollton_99_sup1”.

In signature editor dialog box

1. Click “classify”

2. Select “supervised”.

3. Name output file “Carrollton_99_sup1”. Accept defaults for other choices.

4. Click okay.

5. When the classification is complete, click okay.

6. Close the inquire cursor tool.

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Illustration IV:

In the viewer

1. Click the open file icon.

2. Navigate to the workshop directory and select “Carrollton_99_sup1.img”.

3. Click okay.

Within the viewer menu bar

1. Click “view”

2. Select “arrange layers”. There are three “layers” open in the viewer, with the AOI layer on top,

the supervised classification next, and the original 99 image on the bottom.

3. Right click the AOI layer

a. Select “delete layer”

b. Click “apply”

c. Click “close”.

Within the viewer menu bar

1. click “Utility”

2. Select “swipe”. You can now view both the original 99 scene and the supervised classification,

and evaluate the classification for accuracy.

Ideally at this point you would jump in a car or aircraft and go perform the “ground truth”. You

would refine your classification several times, and perform an accuracy assessment as well.

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Exercise 5 Evaluation and Editing of Supervised Classification

Your viewer should contain two layers: the original 99 scene and the supervised classification. You should

have the swipe function activated. We will be adding new signatures to the signature file to upgrade the

classification. Make sure the original image, not the classification, is “on top” in the viewer. You cannot get

new signatures from the classification – only from the image.

1. Click on the Classifier icon on the main icon panel

2. Select signature editor.

Open the signature file “carrollton_99_sup1” from the C:\Land_cover_tutorial folder.

1. Within the viewer menu bar, click “AOI”

2. Select “Seed Properties” to open the “Region Growing Properties” panel.

3. Change “neighborhood” to “eight neighborhood mode”.

4. Click on the area and set it to “1000” pixels.

5. Save the signature file as “carrollton_99_sup2”, to ATE workshop folder.

6. Activate the “inquire cursor” tool panel, and input UTM 680005 and 3715748 for X and Y.

7. Enlarge this area by dragging a box around the lake.

Illustration I:

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8. Reselect the arrow icon on the viewer tool bar.

9. Activate the “swipe” to by clicking on “Utility” in the viewer panel, and drag the classification

across the lake in the center of the viewer. Is ALL of the water classified as water? If not, create

a new signature as in the previous exercise. You must make sure the image is the top layer in

the viewer, or ERDAS will try to classify the classification, with disturbing results.

10. Activate the “Inquire Cursor” tool by clicking on the + in the viewer icon panel, and input UTM

680207 and 3715712.

11. Within the “region growing properties” panel Set “Spectral Euclidian Distance” (SED) to 5.00.

12. Click “Grow at Inquire”.

13. Reset “SED” to 10.00

14. Click “redo” (not “grow at inquire”!!!!).



water signature.

2. Click once on Class 11

3. Type in “water2”.

4. Click the color patch and select blue.

There seem to be a lot of red “roads” in the scene.

1. Activate the “inquire cursor” tool

2. Input UTM 680349 and 3716508 for X and Y. This broad area most likely represents the

“commercial/industrial” class.

3. Click “grow at inquire” adjusting the SED until you have > 7 pixels.


1. Click on “Create new signature from AOI” tool (third from the left). This adds your new

signature.


3. Type in “commercial/industrial2”.

4. Click the color patch and select yellow.

There seems to be a lot of residential mixed with obvious industrial.

1. Activate the “inquire cursor” tool

2. Input 680248, 3714733. This broad area most likely represents the “commercial/industrial” class.

3. Click “grow at inquire” adjusting the SED until you have > 7 pixels.

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signature.


3. Type in “commercial/industrial3”.

4. Click the color patch and select yellow.

Save signature editor to ATE workshop folder as “carrollton_99_sup2”.

In signature editor dialog box

1. Click “classify”; Select “supervised”.

2. Name output file “carrollton_99_sup2”.

3. Accept other defaults.

4. Click okay.

5. Close the signature editor and the region growing properties dialog boxes.

In a new viewer

1. Navigate to the workshop directory

2. Select “carrollton_99_sup2.img”.

3. Click okay.

In the new viewer menu bar

1. Click “view”; Select “tile viewers”.

2. Visually compare the new classification with the old.

Illustration II:

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After doing this kind of “obvious” evaluation of accuracy, you would again go to the field and

perform “field checking” of questionable areas, and of the classification accuracy in general.

You would lay out a field program for field checking, and you might even hop in an aircraft

and do overflights to assess the classification. Let your motto be:

THEY DON’T CALL IT “GROUND TRUTH” FOR NOTHING!

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Exercise 6

Merging Classes

You will merge the “repeats” within the classification in this exercise, so that the final classification has 9 only classes.

1. Open carrollton_99_sup2.img in a viewer.

From the main icon panel 1. Click “Interpreter” 2. Select “GIS Analysis” > “Recode”. 3. For the input file select carrollton_99_sup2.img. 4. Type in carrollton_99_recode_sup.img for the output file. 5. Click “Setup Recode” button. 6. In the “Thematic Recode” dialog box, notice that the column titles are the same as those present in

the Raster Attribute Editor. 7. Using the shift key

a. Click on duplicate rows b. Give them the same numbers, changing the “New Value” appropriately and clicking

“Change Selected Rows”. 8. Repeat this process, remembering to assign new numbers in the New Value area. 9. Make sure to recode sequentially and do not leave gaps in the sequence. 10. Click okay in the “Thematic Recode” dialog box 11. Click okay in the “Recode” dialog.

Display “carrollton_99_recode_sup2.img” in a new viewer. The colors are not still assigned correctly, and you will fix them in the “Raster Attribute” editor.

12. Display the “Raster Attribute Editor”. 13. Using the column icon

c. Open the Column Properties dialog box d. Add a new column for “class names”. e. Make the “Type” = “String”. f. Set “display width” to 10. g. Move this to the top, and move the color next in line. h. Click okay.

14. Save the changes to your the Raster Attribute Editor 15. Write down the class names and associated numbers for later use. 16. Close the editor.

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Exercise 7 Change Detection

1. In the main icon panel, click “Interpreter”, select “Utilities”, and select “Change Detection”. Next

to the “Before Image” field, navigate to the “C:\Land_cover_tutorial” and select

“carrollton89sub.img”. For the “After Image” field, click and select “carrollton99sub.img”. Next

to the “Image Difference” field, click folder icon and type filename: “carrollton_diff_89_99”.

Click okay twice. Next to the “Highlight Change” Field, click folder icon and type

“carrollton_change_89_99”. Click okay twice.

Under “Highlight Changes”, accept default settings. Note a 10% or greater increase in reflectance

will be shown in green. A decrease by 10% or more will be shown in red. Click Okay.

Illustration I

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2. When done, open “carrollton_change_89_99”. In the same viewer, open

carrollton_99_recode_sup2.img.

3. Open a new viewer, open “carrollton_89_sub.img” AND the change scene

“carrollton_change_89_99.img”.

4. Click view, and select tile viewers. Click view again, and select “link/unlink

viewers>geographical”.

5. Click once in the opposite viewer. Click “Utility”, select “Swipe”, move panel above viewer, then

repeat for opposite viewer.

Illustration II:

6. Activate “Inquire Cursor” in one viewer and type 675663, 3720889 for x and y coordinates.

7. Minimize “Inquire Cursor” dialogue.

8. In the viewer on the right, determine the original land cover of the 89 image. In the viewer on the

left, use the swipe function to determine new land cover in the changed area.

________________________________________________________________________

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9. Maximize “Inquire Cursor” and type 676947, 3721504 for x and y coordinates and determine land

cover change.

10. In the “Inquire Cursor”, type 674307, 3715738.

11. Select the magnifier tool in both viewers, click once on the crosshairs. What sort of land cover

change has taken place in this area? _______________________________________

_________________________________________________________________________

12. Move the “Inquire Cursor” tool to 677267, 3715182. What sort of land cover has taken place in this

area? _________________________________________________________

_________________________________________________________________________

13. Fit image to window in both viewers. In the “Inquirer Cursor” type 673634, 3720426. What sort of

land cover change has taken place in this area? ________________________

_________________________________________________________________________

14. In the “Inquire Cursor” type: 680205, 3715736. Remember this lake? What land cover change

occurred here between 89-99? How does this relate to out three-year drought?

________________________________________________________________________

________________________________________________________________________

15. In the “Inquirer Cursor” type 678725, 3714547. Select the magnifier tool and click twice on

crosshairs in each viewer. Note the large red (decreased reflectance) patch beneath the crosshairs.

Also note the large green (increased reflectance) patch directly to the north. Hypothesize land cover

change trends in this area. (Further discussion upon completion of exercise).

_______________________________________________________________

_________________________________________________________________________

16. Explore the viewer for other types of land cover changes, noting UTM coordinates.

_________________________________________________________________________________

_________________________________________________________________________________

_________________________________________________________

17. Close both viewers.

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Exercise 8 Filtering and Raster to Vector Conversion

1. Open “carrollon_99_recode_sup.img”.

2. Click Interpreter from the main icon panel,

a. Select “Image Interpreter”

b. Select“GIS Analysis”,

c. Select “Neighborhood”.

d. Designate “carrollton_99_recode_sup.img” as the Input file

e. Designate “carrollton_99_filter” s the Output file

f. Accept default settings.

g. Click okay.

3. When modeler is complete

a. Open a new viewer

b. Open filtered image.

4. Click “View”

5. Select “tile viewers”.

6. Compare the filtered and unfiltered versions.

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7. In main icon panel

a. Click “Vector”

b. Select “Raster to Vector”.

c. Designate “carrollton_99_filter” as the Input raster file

d. Designate “carr99lndcvr” as the Output file

e. Click okay.

8. In raster to ArcInfo dialogue box

a. Accept defaults

b. Click okay

c. Verify output coverage type selected is “polygon”).

d. Click okay.

9. Close viewers

10. Close ERDAS.

30

Exercise 9 Display Classification in a GIS

1. Open ArcMap, and click okay in the box.

2. Add new data by clicking the “plus” icon. Navigate to the “C:\Land_cover_tutorial” and click

once on “carr99lndcvr”, and click add.

3. Right click on the layer name and select properties then select the symbology tab.

Illustration I:

Under the “show” index on the left, click “categories” and then click “unique values”. Under the

value field choose “GRID-CODE”. Click “add all values” at the lower left.

4. Assign labels by clicking once in the label column under grid code. Start with number 1 (water) and

refer to your list from the previous exercise to label each grid code (class).

5. Assign colors by clicking twice in the color patch under the symbol column. In the symbol selector

dialog box, click on “fill color” under options. Choose lapis lazuli for water (#1). Change “outline

width” to zero. Click okay.

31

Illustration II

6. Change the other colors as follows: Deciduous trees = peacock green. Change outline width to

zero (for all). Evergreen trees = Chrysophase (green). Grass = medium apple. Wetlands =

black. Bare Ground = electron gold. Residential = rose quartz. Commercial = solar. Roads =

Mars red.

7. Click “apply”, and then click okay.

8. Add data by clicking the plus sign and navigate to ATE_workshop and choose

“carrollton_99_sup_filter.img”. Click “Add”.

9. In the table on of contents, compare the two maps by checking and unchecking the box beside the top

layer name.

10. Click save file icon and name carr99lndcvr_GIS. Click save.

exercise 1 subsetting an image - portland state...

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