Tutorial Supplement

James S. Aber


The following instructions are intended to supplement the tutorial exercises supplied with Idrisi Andes. The tutorial exercises are found in a pdf file--see Idrisi Andes Tutorial, by J. Ronald Eastman (Idrisi Andes\Documentation\Andes Tutorial.pdf). See also manual on Idrisi Andes Guide to GIS and Image Processing, by J. Ronald Eastman (Idrisi Andes\Documentation\Andes Manual.pdf).

Students should follow the step-by-step procedures provided in the tutorial exercises, except as noted below. Additional hints or suggestions are given according to lettered sections of the tutorials. Numbered questions are given below for some exercises. Students should provide written answers for these questions.

To turn in exercise results, students should submit digital files (as e-mail attachments). For text files, plain (ascii) text (txt) or rich text format (rtf) are acceptable formats. Do not send WordPerfect, Microsoft Word, or other proprietary formats. Image files can be sent separately as bmp (in 256 colors), gif, or jpeg formats. Do not embed image files in text documents.

Table of Contents
Exercise 1-1 Exercise 1-2
Exercise 1-3 Exercise 1-4
Exercise 1-5 Exercise 1-6
Exercise 1-7 Exercise 1-8
Exercise 2-2 Exercise 2-3

Exercise 1-1. The IDRISI Environment

This tutorial introduces the basic working environment for Idrisi.

b) Depending on your monitor resolution, the Explorer option may appear only as a narrow bar on the left side of the Idrisi window. Click the [+] sign at the top of this bar to display the full menu. You can expand the display by dragging the right margin to the right. You may click the [-] sign later to remove the full display.

d) Idrisi files, maps, images, and related data are organized according to projects. These projects consist of files arranged in working folders and resource folders which are accessed during project operations.

The working folder is the location where files may be input or output. This is the folder where map and image files may be saved. Only one working folder can be accessed for a project. The resource folder is a location from which files can be accessed and brought into a project session. However, files cannot be saved to a resource folder. Several resource folders can be open during a project session. In this way, available map and image files can be input from several resource folders as well as the working folder for an Idrisi project.

For using Idrisi tutorials, the source files (in the Idrisi Tutorial folder) should be set up as resource folders. The working folder should be designated as the student's personal folder, separate from the Idrisi Tutorial folder. In this manner, no permanent changes would be introduced into the original tutorial files.

Set the working folder to your personal student folder at this time, and move Idrisi Tutorial\Using Idrisi\ to the resource folder list. Keep in mind this change in the project environment.

e) The project environment should now show your personal student folder as the working folder. Idrisi Tutorial\Using Idrisi\ and Idrisi Tutorial\Introductory GIS\ should be listed as resource folders.

Note: in the GSA lab, several students may use Idrisi on the same computer. Be sure to check the project environment every time, to be sure you are working in your own folder.

o) The representative fraction (RF) is the map scale as displayed on the monitor. The scale thus depends on monitor settings (resolution) as well as the size of the map display.

1. What is the RF for the SIERRADEM map in its original display size?

2. Now click the "maximize display" key (7th button from left); you can also click the "end" key. What happened to the image? What is the new RF?

q) This section introduces new Idrisi on-screen functions, measure length and measure zone. Experiment with these functions.

3. What is the distance from the upper left corner of the map to the lower right corner? What are the units of measurement for distance and area on this map?

v) At this point, you should have a map composition that resembles the following example, which is a digital elevation model for a portion of Spain. Elevation is displayed by a combination of colored classes and contour lines. High elevations are depicted in hot colors which appear to stand up above the cool colors of lower elevations. This is a color stereographic effect.


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Now, add your name to the title (or subtitle) for the combined CONTOURS raster and vector display. To do this, select Map Properties in the Composer box. Click on the "Titles" tab, and enter your name in the title line (or subtitle), then click the OK button. You may need to reposition or resize some of the map composition elements. Hint: double click on the feature to move it or resize it.

Save the resulting image as a bitmap (bmp) file using the Composer box. You should now be able to display the bitmap file with any graphics software, such as Paint, Adobe Photoshop, etc. Hint: to reduce the size of the bmp file, convert it to jpeg (jpg) format.

x) This is a strange looking image. It's an example of a false-color image, which in this case resembles color-infrared photography. In this type of false-color composite, active vegetation appears in red and pink colors. Bare soil, rock, and pavement are light blue/cyan.

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Exercise 1-2. Display: Layers and Group Files

A map may display many "layers" of data, such as landuse, political boundaries, streams and lakes, transportation routes, and elevations. This exercise demonstrates how a map is constructed from raster and vector layers. The method of group files is also introduced. The approach allows simultaneous access to data from related datasets for the same map area.

Remember: Set the working folder to your personal student folder, and designate the Idrisi Tutorial\Using Idrisi\ folder as the resource folder.

f) Following this section, save an image of your map composition showing the forest vector overlay on the forest NDVI image. Give your composition a suitable title and include your name and date. Name the saved image "sierraforest."

g) Partway through this long section, the instructions say to "Rename" the newly created raster group file. Give "Sierra" as the new name. Note: this raster group file is located in the Using Idrisi resource folder, not in your personal student folder.

h) This is another example of false-color composite (see above). In this case, the selected bands and color coding produce an image in which active vegetation has yellow-green to dark green colors.

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Exercise 1-3. Display: Layer Interaction Effects

Advanced layer display effects include blends, transparency, anaglyphs, and composites. These visualization techinques are demonstrated in this exercise. Hillshade and reclass operations are introduced as well.

Remember: Set the working folder to your personal student folder, and designate the Idrisi Tutorial\Using Idrisi\ folder as the resource folder.

b) Hillshade creates an artificial illumination that highlights and shadows the "landscape" generated by the digital elevation model. The effect is quite good for creating a sensation of depth.

1. What is the apparent direction of solar illumination for the hillshade image?

c) At the end of this section, you should have a map that resembles the following example. This composition includes a digital elevation model, hillshade image, and pale contour lines, with a legend that shows contour intervals. If your image does not look like this one, back up and repeat the procedures of part c).


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d) Display the SIERRA4 image with the "greyscale" palette. There is one large lake in the upper right corner, and three much smaller lakes elsewhere in the scene.

g) After completing your display of lakes on the Sierra terrain model, save a map composition. The composition should include a suitable title, your name and date. In addition, place a scale bar below the map. The bar should be 10,000 meters long. Save an image named "sierralake" to turn in.

h) Another example of a false-color composite (see above). In this case, the selected bands and color coding produce an image in which active vegetation has blue and cyan colors. This and previous examples were acquired by the Landsat satellite system--see Landsat.

i) This visual effect is also called parallax. When the same scene is photographed or viewed from different vantage points, the relative positions of objects appears to be offset. This is the basis of stereoscopic vision in humans, which allows us to perceive depth. Ikonos is a commerical satellite system that provides high-resolution imagery in visible and near-infrared portions of the spectrum. The resolution of these images equals conventional airphotos, as this example demonstrates. See Ikonos.

j) For proper depth perception, place the red filter over left eye and cyan filter over right eye (see top drawer map case). Maximize the image display and zoom in for best effect.

2. Describe the appearance of the anaglyph image.

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Exercise 1-4. Display: Surfaces -- Fly Through and Illumination

This tutorial demonstrates the ability to visually "fly through" a simulated 3-d terrain.

Remember: Set the working folder to your personal student folder, and designate the Idrisi Tutorial\Using Idrisi\ folder as the resource folder.

c) Click the "Start window maximized" option for the fly-through demo. This will enlarge the simulation to fill the monitor screen.

1. What is a triangulated irregular network (TIN)?

d) The drape image is a false-color composite Landsat image in which active vegetation appears in pink/red colors. The necessary flight file (sf.csv) is located in the Using Idrisi resource folder. This flight begins to the south in the vicinity of San Jose and Santa Clara and proceeds northward into the San Francisco Bay region; the Bay area is home to several million people.

g) Following this step, create a block model of the scene using ORTHO. Select SIERRADEM as the surface image, and pick SIERRAILLUMINATED as the drape image. Choose output resolution of 800 x 600. Name the output image "sierrafire." Leave other options in default values, and click OK.

Add an appropriate title and subtitle (your name and date). North arrow and scale bar are generally not included on this type of perspective view. Note: change background of titles to black, matching the background of the image, and change font color to silver. Save a digital image file to turn in.

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Exercise 1-5. Display: Navigating Map Query

This exercise deals with map queries, that is obtaining information from map layers about specific features (polygons or cells) of interest. The ability to query map information is enhanced by using data layers from a group collection.

Remember: Set the working folder to your personal student folder, and designate the Idrisi Tutorial/Using Idrisi folder as the resource folder.

a) To begin, SIERRA234 should be displayed from the "Sierra" group. In the Idrisi Tutorial/Using Idrisi folder, click the Sierra entry from [+] to [-] to show sublist of included files.

1. What is a "primary" color? What is the "additive" nature of primary colors?

b) Click off legend and title for these displays.

2. What is autoscaling? How does it work?

f) The Group Link icon is 10th from left on the tool bar.

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Exercise 1-6. Map Composition

An effective map display consists of much more than the map image itself. Standard accessories include a scale bar, legend, north arrow, titles, captions, and date. The "map" often contains several layers of information that are overlaid for visual display, as you have seen in previous examples. This exercise deals with building map compositions from these various components.

Remember: Set the working folder to your personal student folder, and designate the Idrisi Tutorial/Using Idrisi folder as the resource folder.

b) You should have a map composition similar to this example. The composition consists of a raster layer as the "base map" plus two vector overlays. Also included are a title and a legend for land use.


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As you proceed through this tutorial, save your map composition periodically. Under Composer, click on the "Save" button. Then select, "Save composition to MAP file" using the name WESTBORO. See n) and o) for more details below.

d) The legend for roads may not be visible at first. Try expanding the size of the display window; drag right margin to right. The road legend may appear to the right of the landuse legend. Reposition road legend below the landuse legend.

f) The "Captions text" input box is found under the "Titles" tab of Map Properties. Follow instructions. Then add your name and date in the input box for "Subtitle text." Select Arial font, maroon color, bold, and size = 12. You may have to move and resize title and subtitle components on the map composition in order to achieve effective placement. Make sure titles do not overlap parts of other components.

g) The WESTBORO.BMP file is located in the Idrisi Tutorial/Using Idrisi folder. The graphic image may not be visible at first; it could be hidden underneath the main map image. Move the map image to locate the graphic inset image. Next move the graphic inset image below the roads legend, then move the main map back into its original position.

Note: the graphic image should be the same shape as the raster "base map" image--approximately square. When moving or resizing the inset image, make sure to retain its square shape.

h) At this point, you have completed most of the standard components of a map composition. Further steps will complete the composition.

Note: sometimes the scale bar does not display properly. If this happens click off the roads and road text layers, then try the scale bar. Once scale bar is correct, then click on the roads and road text again.

l) Do not place a north arrow on your map display. The presence of a grid provides sufficient orientation for the map.

o) Your WESTBORO map composition file should be located in your personal working folder.

p) Instead of printing a paper copy, students should save a graphic image. In the Save Composition menu, select "Save to Windows bitmap (BMP)." Enter WESTBORO as the file name, and click OK. The bmp file will be saved in your personal working folder.

Idrisi cannot display bitmap images directly, but you can view your bmp image with any graphics software, such as Paint, Adobe Photoshop, etc. Display the WESTBORO.BMP file with available graphics software. It should look identical to the Idrisi map composition. Use the image attributes or size function of your graphics software to determine the number of rows (height) and columns (width) in pixels for the bmp image.

1. How many rows and columns does your bmp image contain?

Now check the size of the bmp file in bytes. Use your computer's file management to view file details. Note: one kilobyte (KB) = 1024 bytes. Compare the file size (in bytes) to its size in terms of the number of pixels (rows x columns).

2. What is the size of your bmp file in bytes? How does file size in bytes compare to the number of pixels in the image?

Now open the WESTBORO.BMP file using Paint software (under Windows Accessories). Under the File menu, select the "Save As" option. Notice the file type given in the input box at bottom of window. The current file type is listed as "24-bit Bitmap." This is so-called true color, in which red, green, and blue color values are stored for each pixel in the image. Each color value is stored as one byte (8-bits), so 24 bits are required per pixel.

Change the file type to "256 Color Bitmap" selection, and enter a new file name, such as WESTBORO-256. Click the "Save" button. A warning message will appear; click "Yes" to continue.

3. What happened to the colors of your 256-color image? What is the new file size (in bytes) and how does this compare with the previous (24-bit) size?

BMP files are large in size, as a numerical value is stored for each pixel in the image. This is often redundant, as adjacent pixels may have identical values. More compact storage is possible with various graphics compression formats, such as graphic interchange format (GIF) and joint photographic experts group (JPEG or JPG). Convert your bmp file to one of these formats using your graphics software.

4. What reduction in file size (in bytes) were you able to achieve?

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Exercise 1-7. Palettes, Symbols and Creating Text Layers

A typical GIS database contains spatially georeferenced information about certain attributes or features. This numerical dataset cannot be displayed on its own. In order to create a display, the geographic dataset needs to be translated into colors and visual symbols. In addition, map displays often contain text labels--names of cities, rivers, soils, provinces, etc. This tutorial deals with the creation of color palettes, symbol files, and text layers.

Remember: Set the working folder to your personal student folder, and designate the Idrisi Tutorial/Using Idrisi folder as the resource folder.

a) Symbol workshop is the third icon from left on the toolbar.

h) At this point, you should have a map of Ethiopia that resembles the following example. The ETDEM palette is an example of a "continuous palette," in other words colors vary continuously or gradually from minimum to maximum values.


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1. Why do you suppose these particular colors were chosen to create the ETDEM palette?

2. Why is a continuous palette suitable for displaying a digital elevation model (DEM)?

m) Following this step, you might want to save a preliminary map composition (*.map file). Do this periodically as you move through the exercise.

n) After selecting "text" type and entering the new file name, click OK. The symbol workshop will reappear with a matrix of cells. Click on cell 0 (zero). Another dialog box will appear, in which you can choose font characteristics.

p) Be sure to select PROVTEXT as the symbol file. For the first province name, enter "Tigray" (not all caps), and continue the same way for other provinces.

r) This procedure is a bit tricky. You may have to try a couple of times to rotate the Shewa label.

t) Additional map components include an appropriate title, subtitle with your name and date, scale bar, and north arrow. Under titles, select the caption option to create a caption for the legend. Place the north arrow in the upper-left corner of the black map area; locate the scale bar in the lower-right corner of the black map area.

Note: the order in which you add components is important. Save the north arrow as the last thing to add, after titles and scale bar. You should change background and font colors to place legend caption, scale bar, and north arrow on the black background.

3. Why does the scale bar show degrees instead of a linear measurement, such as meters, kilometers or miles? Hint: see etdem.rst metadata.

u) Along with the map composition, save a digital image file, named ETHIOPIA.

v) This Landsat false-color composite of Las Piedras, Venezuela utilizes spectral bands and color coding so that active vegetation appears in green and yellow-green colors.

w) The photo layer is a new capability of Idrisi; this is an excellent tool for field operations. You may have to expand each window for photos to see the full titles. Notice the extremely steep terrain in this region.

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Exercise 1-8. Data Structures and Scaling

GIS databases come in two basic types--raster and vector, which require quite different file formats and structures. This tutorial explores the characteristics of files employed in Idrisi for these data types. The tutorial also deals with means for "scaling" data values for display.

Remember: Set the working folder to your personal student folder, and designate the Idrisi Tutorial/Using Idrisi folder as the resource folder.

b) WESTLUSE and ETDEM raster files are located in the Idrisi Tutorial/Using Idrisi folder.

e) Read through this long section carefully.

1. What are ASCII and UNICODE file formats?

g) Examine the metadata for ETDEM and note the entries for reference system, reference units, min/max x and y, min/max value, resolution, and value units. The distinction between these file attributes is important.

2. Explain the meaning of reference system, reference units, min/max x and y, min/max value, and value units in the ETDEM metadata file.

3. Why are reference units in degrees and value units in meters?

4. What do the values for resolution represent?

Following step (l), create a new false-color composite for the Sierra Landsat dataset. Find and open the COMPOSITE icon (5th from left on tool bar). Enter sierra2 as the blue band, sierra 5 as the green band, and sierra7 as the red band. Sierra 2 actually represents green light, sierra 5 and 7 are both mid-infrared radiation. Name the output file sierra257, and enter a suitable title. Leave other options in default mode, and click OK.


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You should have a false-color composite similar to the example above. This selection of bands and color coding produces a naturalistic portrayal in which active vegetation is green, water bodies are blue, and non-vegetated land is tan, yellow or white. Prepare a map composition that includes a suitable title, subtitle with your name and date, and scale bar. Save a digital file named SIERRA257 to turn in.

m) WESTROAD vector file is located in the Idrisi Tutorial/Using Idrisi folder.

n) The term "double precision real number" is mentioned in this part. Look up the meaning of this numerical format in the Help/Contents--see file structures: vector file.

5. What is the difference between single and double precision real numbers?

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Exercise 2-2. Datebase Query

This exercise deals with extracting information from multiple layers of data, such that compound conditions can be identified. In this case, the combination of elevation and soil type is necessary for determining the feasibility of an agricultural project. You will utilize the cartographic model approach to building a sequence of operations to be carried out on the datasets. See Tutorial 2-1 for an explanation of cartographic models.

Note: Answers for the numbered questions (1-8) in the tutorial are given at the end of the exercise. Be sure to confirm your answers.

a) Set up a project in your own student folder. Add Introductory GIS as a resource folder for the project. See footnote 48 at bottom of p. 56.

o) As you can see, there is no difference between PLOTS and PLOTS2. This is because background values (0) were ignored by GROUP. So you can eliminate the step to create PLOTS2 for the macro model (below).

After working through the exercise step by step, you should build a complete macro model to run the procedure from start to finish--input files to PLOTS. Do not include AREA or EXTRACT operations. See p. 65, and consult Figures 4, 5, 7 & 8 for guidance.

Build your macro model from left to right, and test it each time you add a new element. Save the file, and run. A warning message may appear about overwriting existing files; click "yes to all" button.

Once you have completed a successful macro model, save the model diagram. Under "File" click "Save to clipboard" option. Then open the Windows program Paint, and paste the image into Paint. From here you can save the image as a jpg or gif file to turn in.

Skip the section on "Using image calculator ..." (p. 67).

As your final task, make a map composition of the suitable soil plots for sorghum. The background should have a dull brown color, and each plot should have a distinctive yellow, orange or green color. You will have to make a special palette using the Symbol Workshop (3rd icon from left). The composition should include a suitable title, subtitle with your name and date, legend and scale bar. Save an image file to turn in.

Turn in:

Exercise 2-3. Distance and Context Operators

The tutorial exercise demonstrates suitability mapping using distance and context functions. Suitability often involves multiple input datasets and is usually related to proximity of one feature to another, for example proximity of a housing development to a sewage treatment plant in combination with prevailing wind direction. The first step in such an analysis is to identify limiting factors, in other words the suitability criteria. This example is based on choosing a site for a new manufacturing company based on such factors as ground slope, area, proximity to water, and available land.

Remember: Set the working folder to your personal student folder, and designate the Idrisi Tutorial/Introductory GIS folder as the resource folder.

Note: Answers for the numbered questions (1-7) in the tutorial are given at the end of the exercise. Be sure to confirm your answers.

a) Click on "legend" for the ORTHO display.

Following step e) your map of suitable slopes should be like this sample image. All colored cells represent slopes less than 2.5°.
Following step n) your map of suitability should be like this sample image. All colored cells represent suitable combinations of slope, reservoir buffer, and forest land.

o) Use the Qualitative palette with 256 classes and no autoscaling to display the GROUPS image.

p) Note: check AREA module to output hectares for group areas. Further improvement in display of the GROUPAREA image is possible. Use the Qualitative palette. Under autoscaling options, select "Equal intervals" and set "Number of classes" = 16, then apply. At this point, you should be able to identify the specific area that meets all criteria for the manufacturing plant.

q-r) With a proper RECLASS operation, you can move directly from the GROUPAREA image to SUITABLE. Name your reclass file, suitable.rcl, and submit.

Once you have completed a successful macro model, save the model diagram to turn in. For the final map composition, create a special palette in which the unsuitable background is a dull green color and the suitable area appears bright yellow-orange. Additional elements to include are a title, subtitle (your name and date), legend captions, north arrow and scale bar (with appropriate units). Turn in your final composition as a digital image file.

Turn in:

Return to ES 351, ES 551, ES 555, ES 771, or ES 775.
© J.S. Aber (2008), Emporia State University.