Tutorial Supplement

James S. Aber


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

Students should follow the step-by-step procedures provided in the tutorial exercises (Taiga Tutorial.pdf), 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, 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 1-1. 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.

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. In step p), click the icon for Full Extent Maximized (9th icon from left). 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 for 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.


Click for larger display

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.

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.

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.

Turn in:

Exercise 1-2. Display: Layers and Group Files

A map may display many "layers" of data, such as land use, political boundaries, streams and lakes, soils and geology, transportation routes, elevations, etc. 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.

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

Note: Taiga has improved pan and zoom functions compared with previous versions of Idrisi.

f) Following this section, save an image of your map composition showing the forest vector overlay as a dark-blue cross-hatched pattern on the forest NDVI image. Give your composition a suitable title, including your name and date, and save an image file (bmp). Name the saved image "sierraforest."

g) Partway through this long section, the instructions say to "Rename" the newly created raster group file. Note: this raster group file is located in the Using Idrisi resource folder, not in your personal student folder. It may appear that two "sierra.rgf" files have been created, but this is not the case--only one actually exists.

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.

Turn in:

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) Be sure to select the "Analytical hillshading" option in the SURFACE module. Hillshading 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 blue 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).


Click for larger display

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.

e) The RECLASS icon is actually fifth from right across the top tool bar.

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.

Turn in:

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.

Turn in:

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. This is a false-color composite, as noted above.

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 11th from left on the tool bar, and Placemarks is the 12th icon.

Turn in:

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.


Click for larger display

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, or it may be partly hidden behind the raster layer or landuse legend. 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 the map or 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) You might want to give the scale bar larger font, depending on its visibility and the resolution of your monitor. 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.


Click for larger display

At this point, you have completed most of the standard components of a map composition. Remember to save your composition frequently as you are working on it. Further steps will complete the composition.

i) The graphic inset may disappear (turn gray) when you apply the background color. If this happens, remove the graphic inset, and then restore it.

l) Place the north arrow below the scale bar and above the graphic inset. You may need to resize it in order to fit.

n, 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 Taiga 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?

Turn in:

Return to ES 351, ES 551, ES 555, ES 771, or ES 775.
© J.S. Aber (2009), Emporia State University.