Geography 372

Geography 372

Lab 3: Visual Data Analysis

Background: This lab exercise will introduce you to the Environment for Visualizing Images (ENVI). ENVI is state-of-the-art image processing software that is designed to provide comprehensive analysis of satellite and aircraft remote sensing images. There are many different software packages that are available to handle remotely sensed images. Often these software packages have certain strengths and weaknesses. ENVI is one of the more user-friendly packages and is especially good at dealing with hyperspectral imagery.

No late labs can be accepted. Please type the answers just below the questions and hand the printouts at the beginning of the next lab: September 26th (0102) and 27th (0101)

First, we need to open ENVI. You will find ENVI under Start and then go to programs. When it opens you should have a tool bar across the top of your screen. To begin, take a few minutes and familiarize yourself with some of ENVI's pull down menus and options. Simply use your mouse to explore the graphical user interface (GUI) or ENVI's main menu bar (this is what should be on your screen).

ENVI is quite an intuitive software package but if you get stuck you can refer to the help. Trial and error is the best way to learn. Most of the commands we will use in this lab can be accessed through the File menu on the main menu bar or through the Tools menu on the image. This lab will also expose you to one source of satellite imagery. The imagery we will be using in this lab was acquired by Dr. C. J. Tucker through NASA's ESE SDP Program.

When you are ready to look at the image, go to the U: Instruction drive 372-fall07 folder. The images are located in the lab3data folder.

Now you can open the image. In Envi: - File - open image file – then navigate to the location above and select the file named lab3_subset - open

Load the image – click the RGB Color button, load Band 3 - R, Band 2 - G, Band 1 - B

Do this simply by clicking on the bands in the band list in the order you want them to appear.

When the image loads, an ENVI image display will appear on your screen. The display consists of an Image window, a Scroll window, and a Zoom window. These three windows are intimately linked; changes to one window will be mirrored in the others. All windows can be resized by grabbing and dragging a window corner with the left mouse button.

1. What is this band combination called?

2. What projection is this image in (File - Edit ENVI header)?

3. How many channels/bands does this image have?

4. What is the size of a pixel in this image?

5. What is the source of this image? (i.e. landsat, ikonos, etc. Try: http://www.digitalglobe.com/product/basic_imagery.shtml )

6. What are the spectral bandwidths and locations of the four channels (give your answer in um)?

7. Now look at the image and try to find the IKEA store. What are the coordinates in lat/long (LL) of the new IKEA? Was the construction completed before or after this image was taken?

Load each band individually, beginning with band 1 (remember to click gray scale):

8. Which band produces the most noticeable visual contrast? Why do you think this is?

Reload the image - click RGB Color, load Band 3 - R, Band 2 - G, Band 1 - B
Set your cursor on the following location by entering the following x/y image coordinates:

394, 2055 (go to tools - pixel locator)

9. Describe what you can see in the immediate surrounding area, i.e. describe the vegetation

Leave your cursor in the same location and put band 4 in R, band 3 in G, band 2 in B:
10. What is this band combination called?

11. Now describe what you can see in this area? Why do you think you see this?

Analyze the vegetated area running parallel to Rt193 (on right heading to Rt1), extending between 515, 2257 and 592, 2182:

12. Describe the area

13. What weather-related phenomenon occurred on September 24, 2001 that could have resulted in this patch characteristic?

Set your cursor on the following location, 1298, 2601:

14. If a bright sand soil were added to one of the objects how do you think this would impact the reflectance and why?

Set your cursor on the following location, 753, 1554:
15. What are the rectangular shaped objects in this general area?

16. Why do you think they appear as different colors?

17. What happens when you change the band combination?