Idrisi Assignments

The SURFACE module can derive three surficial characteristics:

  • Slope
  • Aspect
  • Analytical Hillshading (= shaded relief)
To be correct: the last one is not really a surficial characteristic, but akind of synthetical shading of a DEM for illustration purposes only.

In terms of IDRISIthe values in a slope image reflect the maximum slope around each pixel amongfour directions - N, W, E, S. Only these 4 neighbours are taken into account.Be critical of what you get 'at your fingertips', calculations of slopearen't that clear-cut they may seem to be (background reading e.g. BERRY 1993,p. 147ff.*). Be prepared to receive considerably - in terms ofreliability - different results throughout GIS software products treating one and the same dataset.Disturbing, isn't it?

Slopes may either be expressed as decimal degrees (0 - 90�) - - or percent (45� equals to 100%, whereas 90� slopesapproach to infinity) - -in the SURFACE module. Slope images may be used to derive constraint areas, e.g. for planningfactories, roads, ... they are part of predicting soilerosions, or danger of avalanches and so on.Keep in mind that slope computing is by no means strictly restricted to DEM datasets.
Let us now proceed to the aspect images. IDRISIs SURFACE module calculates them as'the direction in which the maximum slope faces'. The values are decimal degrees of type real thatrange between 0� and 360� (N). The direction is clockwise (90� means east, 180� south, ...). Valuesof -1 are assigned to completely flat areas (where slopes are 0).

Last but not least we may simulate the state of illumination for a DEM at given sun azimuth (260 - 290�)resp. elevation angle (0 - 90�). As with the ORTHO-module before we couldapply TRANSPOS to the DEM, rotate it, run the analytical hillshading and rotate the resultingimage back to the origin, thus simulating light sources from any direction. The algorithmic basis ofthe analytical hillshading is a simple combination of trigonometrical calculations with slope, aspect andthe zenith angle. Hillshade images are intended only for visualizations (e.g. enhancing textural anddirectional elements). Values range from 0 to 1 so a STRETCHing to 0 - 255 may be expedient.Notice, that cast shadow is not taken into account!
The following graphic is the 3D-representation of a hillshade draped over the raw DEM. Rivers, lakesand glaciers have been added subsequently in a prevoius step. The blue sky was a little bit tricky buthas been realized completely with IDRISI:


Joseph K. BERRY, 1993: Beyond Mapping: concepts, algorithms,and issues in GIS. GIS World Books, Fort Collins
last modified: | Comments to Eric J. LORUP

 

COMPETENCY EXERCISES

Because each institution has its own network setup, data paths would often differ from those in the tutorial exercises. These differences will be reflected in the project environment file that records the location of input and output data in Idrisi. In our case, the major differences are as follows (also see File Management in class and Idrisi  Demo 1. for details on how to set project environment in Idrisi):

1. All initial data sets for Idrisi Tutorials (competency exercises) are stored locally. Note that drive letters may differ, commonly d: or c:. The Resource Folders (for input data) include TWO folders - d:\Idrisi Tutorial\Using Idrisi and d:\Idrisi Tutorial\Introductory GIS. This is INSTEAD OF one folder c:\Idrisi Tutorial\Introductory GIS as indicated in the Tutorial text book.

2. The Main Working Folder (for output files) should be set as your U:\gissg\compex. Normally, Idrisi tutorial exercises can be done in one session and you do not need to keep the output files. You should delete them from U:\gissg\compex folder unless instructed to do otherwise.

CHECK THESE DATA PATHS EVERY TIME YOU BEGIN AN EXERCISE.

Note that the Idrisi tutorial exercises contain many questions that make sure that you understand what you are doing. Most these questions are for your own use and you do not have to turn in the answers; you only have to answer the questions that will be posted in the GIS SG course schedule (see below). In addition, the correct answers to each tutorial exercise are provided in the end of the exercise but I strongly encourage you not to look at the answers until after you have finished the exercise.

The data for mastery exercises will be made available for downloading from this web site. The output data will be written to a special folder on your U: drive. Instructions will be provided. Again, after you complete the exercise, delete the output datasets to save space on the server.

COMPETENCY EXERCISE 1. 

Idrisi Tutorial exercise 1-1.

Data:

Turn In:

Written answer to the following question: 

In which corner is water located on a three-dimentional view of the terrain in ? To describe the location, use cardinal geographic directions.

Idrisi Tutorial exercises 1-2, 1-3, 1-4, 1-5

Data:

D:\Idrisi Tutorial\Using Idrisi and D:\Idrisi Tutorial\Introductory GIS

Turn in:

Exercise 1-2. Print out the following pages from Idrisi on-line help: 1) definition of Vector  2) Definition of Raster 3) who is Idrisi. 
Print map one of your vector maps and sign your name.

Exercise 1-3 1-5. Just get a sense of how to query collections of layers and display vector and raster files in various ways. Nothing to turn in but these exercises provide you with important skills you will need in future exercises.

It is highly recommended that you start using Idrisi online help as soon as possible. Online help is accessible from the main menu (from here you can also open digital Guide to GIS and IP and Tutorial) and from each dialog box (press Help button). Help is context sensitive and provides useful information about operation of each module. There is also a Glossary of major terms (check this out as well). Many items can be found using Index of the Help System.

NOTE: When instructed to create and save a new raster group file SIERRA.rgf,  first copy all images (along with their documentation files) that you want to include into the group to your main working folder U:\gissg\compex. The problem is that the group file must reside in the same folder as the images that are the members of the collection.

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COMPETENCY EXERCISE 2. Maps

Idrisi Tutorial exercise 1-6, 1-7, 1-8.

Data:

C:\Idrisi Tutorial

Turn in:

Exercise 1-6. Add an extra-title to your map composition that includes your name. Print out the map composition on laser printer in the lab and turn it in. Note that it will print in gray scale only. 

Exercise 1-7. Add an extra-title to your map composition that includes your name. Print out the map composition on laser printer in the lab and turn it in. Note that it will print in gray scale only.

 

Exercise 1-8. Explain in a few sentences what “View structure” command does for raster and vector files.

COMPETENCY EXERCISE 3. Database integration (EXTRA-CREDIT)

Idrisi Tutorial exercises 7-2 and 7-3.

Data:

C:\Idrisi Tutorial

Turn In:

Ex.7-2: Print the map showing discrepancy between STREAMS and DEM. Do not forget to add your name and date. 


Ex. 7-3. Print the map showing the correctly integrated streams and elevation model with your name and date.

NOTE: Before you begin, add folder \Idrisi Tutorial\Database Development to your resource folders. This folder contains DLG files that you will be importing into a GIS.

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COMPETENCY EXERCISE 6. Cartographic modeling and database query.

Idrisi Tutorial exercises 2-1 and 2-2.

Data:

C:\Idrisi Tutorial

Turn In:

1. Written answer to the question: What is the maximum elevation of the potential sorgum plot Group 1? 
2. Printed cartographic model constructed in Macro Modeler. 

To print your model, Use Print button from the Macro Modeler menu.
The model must be annotated with exact reclassification data ranges and new classes, contents of attribute values files, and names of overlay operations.

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COMPETENCY EXERCISE 7a. Distance and context.

Idrisi Tutorial exercise 2-3.

Data:

C:\Idrisi Tutorial

Turn In:

Print out of the final map with the legend and your name. Insert legend captions. Add to the map a textbox that briefly (2-3 sentences) describes the content of this image.

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COMPETENCY EXERCISE 7b. Cost-Distance.

Idrisi Tutorial exercise 2-5.

Data:

c:\Idrisi Tutorial

Turn In:

Print out of the final map with the legend and your name. This map should show the new line (in raster) and location of the plant and the existing power line (add the appropriate vector layers). Insert legend captions. Add to the map a textbox that briefly (2-3 sentences) describes the content of this image. Add a scale bar.

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COMPETENCY EXERCISE 8. Map Algebra.

Idrisi Tutorial exercise 2-6.

Data:

c:\Idrisi Tutorial

Extra-credit 

 Do the optional problem (2pts to the grade for this exercise)

Turn In:

Print out of the final map of agrozones with the legend and your name. Add to the map a textbox that briefly (2-3 sentences) describes the content of this image. 


Submit a fully annotated cartographic model (either handwritten or in micro-modeler). 

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COMPETENCY EXERCISE 9. Multi-criteria evaluation: Non-Boolean approach.

NOTE: THIS EXERCISE IS DUE AFTER COMPETENCY EXERCISES 10 AND 11.

This exercise is 2 points worth.

Idrisi Tutorial exercise 2-7 and 2-8.

Data:

D:\Idrisi Tutorial\MCE

Turn In:

Ex.2-7: Use Image Calculator to build most criteria (Make sure you know what you are doing!)


For sections i), k), and m) write an expression that you would use in Image Calculator to create these constraints. 
Ex.2-8. Draw and label a graph that shows how you standardized the developed land factor.

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Competency exercise 10
Competency exercise 11

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