TEACHING GEOG 385.02/GTECH 785.02 
Back to MP home page

GIS SG course homepage
Back to GIS SG schedule
GIS links and resources
Class Project


List of assignments and exercises


 Setting up working folders in Idrisi and ArcView

Download Data for Mastery Exercise 2. Downloading mastery exercise data.






Please read and follow the instructions in Downloading mastery exercise data on how to create a new project environment file to store your settings for each mastery exercise and to download your data.

Turn In:

1. Written answers to questions 1-4, the print out of your final map (see question 5)
2. A complete handwritten cartographic model of the steps you used with all annotations. Use the conventions shown in Idrisi Tutorial Exercises 2-1 and 2-2 for your cartographic models
3. Print out from the Macro Modeler with the same model. 

NOTE: Please remember that there is a difference between reference units (coordinates measurements) and value units (data measurements). In GIS layers that depict elevation or depth these two might or might not be the same.

The Exercise:

This is the second mastery exercise and the first to test your ability to work independently on solving GIS problems. It assumes that you have completed all the competency exercises assigned up to now and did all the class demos. Demo scripts are avalable from the GIS SG Schedule page. The exercise consists of a data set and a few basic questions that must be answered. These questions will test your ability to query a simple GIS database. In order to answer the questions you will need to use a variety of Idrisi modules that have been covered in class and competency exercises.

This exercise focuses on a problem in fisheries management. The issue concerns the environmental impact of shrimp fishing in Tampa Bay, Florida. Shrimp fishing involves dragging nets behind boats in relatively shallow water. These same shallow waters of the bay also contain "nurseries" for other commercial fish species. The nurseries are sea grass beds that grow on the bottom of the bay and they can be damaged by shrimp nets. This exercise explores the spatial overlap of shrimp fishing and nursery areas.


The first step in this exercise is to explore the database provided by the Florida Marine Research Institute. The first image to explore is called HABITAT. This image was produced from air-photo interpretation and shows differing densities of sea grass beds as well as other habitat categories. Display the raster image HABITAT in Idrisi with a legend, title, and a user defined palette called HABITAT. (To use a user-defined palette, click on the User-Defined radio button, then invoke the pick list from the input box below and choose the desired palette.)


Tampa Bay is on the west coast of Florida. The imagery covers the north half of the bay only, the Gulf of Mexico is to the left, and the main opening in to the bay is at the bottom left of the imagery.


The second image to display was derived from interviewed fishers who drew on nautical charts the areas where they fished. Display the raster image SHRIMP in Idrisi with a legend, title, and the Qualitative palette (you can also use the BW palette for this type of image, BW also good for printing this type of image).


The third and final image in our database was derived from standard nautical charts published by the National Oceanic and Atmospheric Administration (NOAA). An analog (paper) chart of the bay containing coastline data as well as point data showing water depth was digitized. The result was two vector files, one for the coastline and one of all the depth points. To explore these layers, display the vector file called DEPTHS using the symbol file also called DEPTHS and add the layer called COASTLINE using the uniform black symbol file. Highlight the DEPTHS layer on composer, then use the cursor query tool to examine some of the depths. Note that even though these are depths below sea level, the attributes of the points are positive, i.e., an attribute of 8 means the point is 8 ft below sea level.

The vector file of depths was interpolated into a smooth continuous raster surface representing bathymetry (or water depth).


Display the raster image of bathymetry called BATHYMETRY with a legend, title and a user defined palette also called BATHYMETRY. Add to this display the vector layer COASTLINE with the uniform white symbol file for better visual interpretation.


Explore the three main raster images using cursor inquiry and by viewing their Layer Properties. Note the data types, coordinate systems, min and max X/Y, and the underlying values in the images themselves.


Note that in the BATHYMETRY image, water depth is recorded as a negative value, i.e., a cell with the value -8 is 8 ft below sea level. Note also that you will see values of zero depth outside of the coastline. This is due to the number and position of the depth points used for the interpolation as well as the interpolation algorithm used. Donít worry about it for this exercise.


Question 1: What kind of palette is BATHYMETRY? What kind of palette is HABITAT? (quantitative or qualitative)


Question 2: Recall that in class we characterized different raster data as quantitative, qualitative, or Boolean (a particular type of qualitative image). How would you characterize each of the three raster images in this data set?


Question 3: What is the average depth of each sea grass category?


Exploring the data above included two forms of database query (by location). The remaining analysis consists of query by single attribute, and multiple attributes. It is important that you produce a cartographic model showing each step of this analysis. Do not turn in this exercise without a cartographic model detailing the remaining analysis. On the model indicate clearly all images, filenames, and modules used (use the conventions discussed in class and in the Idrisi Tutorial exercise 2-1 which is on reserve in the main office). Also, indicate on your cartographic model the actual values used in any procedure such as RECLASS or Edit/ASSIGN. Also indicate the methods chosen (e.g. OVERLAY multiply, OVERLAY add). Please DO NOT use Image Calculator for this exercise. (We need to master the individual modules first, before we begin using shortcuts like Image Calculator.)


Nursery areas in Tampa Bay that are most vulnerable to shrimp fishing are those that are used by shrimp fishers and have dense sea grass beds (the best areas for young fish of other species) and are in shallow water less than 3 feet in depth (it is more likely that a net dragged in shallow water will damage sea grass beds on the bottom). Note that depths are recorded as mean values at low tide. This means that when tide is not at its low, there is more than 3 ft of water above these areas that we identify as shallow water.


Question 4: What is the area (in hectares) of those locations most vulnerable to shrimp fishing? To answer this question you will have to produce a final image from your analysis showing locations most vulnerable and then calculate their total area (in hectares) using another database query tool. The steps you take to get the final image should be clearly indicated on your cartographic model.

Question 5: Create a map composition based on your final image. Use BW palette, add title, legend and legend captions, and your name. You can add other map components if you wish. Print out your map and turn it in along with the answers to questions 1-4 and the complete cartographic model. Also, print out the output from the Macro Modeler of the same model (save to clipboard, paste to a MS Word file, and then print).

Top of page