Introduction

This lab will get you started with Erdas Imagine. Imagine was designed for various operating systems and platforms, so its interface is different from other Microsoft Windows-based software. This is your opportunity to explore the software and to get acquainted with the interface. Use the help system as well as the field guide to learn about the different software options. Try to repeat the steps or procedures a second time without reading the instructions. This will enforce your memory of how to use the software. You will learn how to set preferences, display an image, query for pixel information, arrange layers, adjust image contrast, link images from different viewers, use AOIs, and use several raster tools.

Instructions

Before you start the first lab, you need to know where to save your lab data. You are only allowed to put data in the C:\users folder on the computers in CH469 or CH475. You can use your odin ID or your name to create a working folder in C:\users so that your data won’t get mixed with other students’. Then copy the lab data to your working folder and do your exercise. For lab 1, you will have to copy the following files to your working folder. You can find these files in I:\Students\Instructors\Geoffrey_Duh\GEOG4581\Lab1.

ColorBlocks.img

eldoatm.img

eldodem.img

hyperspectral.img

lanier.img

lndem.img

lnsoils.img

If you want to access your working folder from other computers on campus, please follow the instructions on this page.

1. Click the window start menu and select “All Programs -> GIS -> Leica Geosystems -> ERDAS Imagine 9.1 -> ERDAS Imagine 9.1” to start the Imagine software.

2. Open the lab book (ERDAS TourGuide9_1.pdf) and skim the Preface of the tour guide (pages xvii to xxvii). The lab book (TourGuide9_1.pdf) is in the I:\Students\Instructors\Geoffrey_Duh\ERDAS Imagine folder. Complete the tutorial exercise in Imagine Essentials section (pages 1 to 61) and answer the questions at the end of this document. Don’t just read the text! Some useful tutorial information is also shown in the figures.

3. After the completion of the tutorial exercises in the tour guide, display the colorblocks.img image in a viewer and use the inquire cursor tool to find the band values on the locations specified in the table at the end of this document. Record the color and values associated with each location in the table. Make sure you set the X, Y coordinate unit to “File”.

1. Write you name, type the answers to all questions, and submit a hardcopy to the instructor by 4pm Jan 25.

Questions

What are the default band-image color channel settings when a viewer displays a Landsat Thematic Mapper (TM) image (e.g., lanier.img)? A TM image has 7 bands. You can set band-image channel default values under the User Interface & Session section of the preferences editor.
Explain three other preferences that you can set that were not discussed in the tutorial. Use the help tools to understand what they do.
What is the difference between the recent and goto options when opening a raster layer?
Explain what might have caused the variations of red-brownish color on the lanier image when you display it using Red=4, Green=5, and Blue=3. Please use the band descriptions and band combinations pages as references.
Display the lanier image several times using different raster options available to you when you open a raster layer. Then answer the following questions.

What does the fit to frame raster option do?
Explain what the image looks like when using the no stretch option and why it looks that way.
Explain the difference between “true color” and “pseudo color” images.
Resampling is used to calculate pixel values when one raster grid must be fitted to another. When a raster image is opened, the raster grid defined by the file must be fit to the grid of screen pixels in the Viewer. All Viewer operations are file-based. Any time you resample in the Viewer, the Viewer uses the file as its source. If you zoom the raster layer, the Viewer resamples the file grid to the new screen grid. The resampling methods available are: nearest neighbor (uses the value of the closest pixel to assign to the output pixel value), bilinear interpolation (uses the data file values of four pixels in a 2 x 2 window to calculate an output value with a bilinear function), and cubic convolution (uses the data file values of 16 pixels in a 4 x 4 window to calculate an output value with a cubic function). When displaying the lanier image using these three different resampling methods (in three viewers) what is the difference in the way they look. You'll need to zoom in on a small area such as one of the bridges using three different viewers. Explain why each looks the way it does based on the different methods described above.

Explore the information available in the cursor inquiry dialog window. In order to understand the different types of information you will need to play with the window and use the help buttons. Explain the different types of information available to you within this window. What happens to this information when you move the cursor?
Use the polyline measurement tool to calculate the approximate width of the lanier image in meters.
Use the perimeter and area measurement tool to calculate the approximate area of the lanier image. Note: you didn't use this tool in the tutorial.
Explain the different zoom options.
How do you think you could use the utility of linking viewers geographically?
What is an AOI? Explain the two different methods you used to create AOIs.
For what can the piecewise contrast tool be used?
Why does the LUT value of Band 2 change when you do a piecewise contrast adjust? Does the original data (file pixel) change?
Print the soilsreport.txt file.
Explain the spectral profile. What do the X and Y axes represent?
Explain the spatial profile tool. What do the X and Y axes represent?

Color code used in the table below:

1: Red, 2: Magenta, 3: Blue, 4: Cyan, 5: Green, 6: Yellow, 7: Gray. If the color is dark blue, then record “Dark 3”. If the color is not in the list, then describe the color with your own word (e.g., cobalt blue).

File X, Y	Color Code*	Blue Band File Pixel DN	Green Band File Pixel DN	Red Band File Pixel DN
30, 30
100, 30
170, 30
240, 30
300, 30
380, 30
450, 30
170, 400
450, 400
What color is this?		0	70	70
What color is this?		0	100	200