After becoming familiar with the display capabilities of Idrisi we will now begin to use it in a GIS study. This exercise will consist of Tutorial 5 from the Idrisi Windows Student Manual. Tutorial 5 introduces the concept of Cartographic Modeling and Database Query. The problem posed involves the finding of areas suitable for a certain type of agriculture in an area of Mauritania along the Senegal River. The criteria for suitability involve a certain combination of soil type and moisture availability, and will be established using the Database Query modules ASSIGN and RECLASS and OVERLAY. ASSIGN and RECLASS are similar and can be used to isolate categories of interest located on any one map. OVERLAY allows us to combines queries from pairs of maps, thereby produce compound queries.
One important concept we will learn in this process is the expression of simple queries as Boolean images (images made up of ones and zeros). These images allow us to use Boolean or logical operation with the arithmetic operations of OVERLAY to perform multiple attribute queries. We will also see how a Boolean image (or Boolean Mask) may be used in an OVERLAY operation to retain certain values and mask out the remaining values by assigning them a value of zero.
For more information on these concepts, refer to the Idrisi Tutorial on WWW at:
and to the On-line Help available within the Idrisi software itself.
With the supervision of your lab instructor or lab coordinator, use
Idrisi for Windows software to
carry out the directions for Tutorial 5 in the Student Manual.
The data for this tutorial is located in the Idrisi for Windows
sample exercise data directory., typically C:\EXERCISE. The path may vary
from PC to PC, so check with the instructor or lab coordinator.
For tutorial 5 on Database Query, answer questions 1 through
8. Prepare your answers in Microsoft Word format. Produce a printed
copy of your answers for your records.
For University of Hartford students, send your Word -formatted answers
to the questions in Tutorial 5 by way of e-mail to:
For students at UConn, submit your work to:
To reinforce the principles learned in Tutorial 5, re-do the analysis
using sandy clays as the most desirable soil, instead of clay. How does
the amount of suitable acres change? Send a copy of the final map (suitable
for insertion into a Word document) electronically to the e-mail
sites listed above.