Lab 2: Download LandSat Image and Make Maps From Satellite Imagery (Due by 4pm Feb 1)

Introduction

In this lab you will learn how to download and save a LandSat image and make maps using the Erdas Imagine Map Composer.

Instructions

Part I. Download a LandSat TM Image

1.      Before you start, create a lab2 folder under your workspace in C:\users folder.

2.      Go to the Landsat.org website (http://www.landsat.org/) and select “Landsat Ortho (FREE)” from the “Search for Imagery” dropdown menu. Follow the instructions on that page and use the “Row-Path Finder” tool to find the Worldwide Reference System II (WRS II) Path/Row numbers of the scene that covers the estuary of the Columbia River. The WRS is a global notation system for Landsat data. It enables a user to inquire about satellite imagery over any portion of the world by specifying a nominal scene center designated by Path and Row numbers. The path in WRS II notation is a sequential number from east to west to identify 233 nominal satellite orbital tracks. Row refers to the latitudinal center line of a frame of imagery (i.e., a scene). You should find a 5-digit number associated with the scene. The first two digits represent the Path number. The following 3 digits represent the Row number. Write down the path and row numbers and close the “Row-Path Finder” tool.

3.      Go back to the FREE Global Orthorectified Landsat Data page and use the Path and Row numbers to navigate to the ftp folder containing the source Thematic Mapper (TM) image files. You will find several .gz and .jpg files, among others. Double-click on the browse.jpg file to verify that you are in the correct data folder. Check the file size of each .gz file. You should pay special attention to the file size of _nn6.tif.gz. If that’s the right folder, then copy and paste the three .gz files with the _nn3.tif, _nn4.tif, _nn5.tif, and _nn6.tif suffixes to your working folder in C:\temp.

4.      Now we need to unzip (decompress) those gz files. Double-click on the gz file and check “Select the program from a list”. Click OK and then click on the “Browse” button. Navigate to “C:\Program Files\7-zip” folder and select “7zFM.exe”. The 7-Zip File Manager window will appear. Click on the Extract icon, specify the lab2 folder as your output folder and click OK. This will unzip the gz file. Repeat these steps to unzip all gz files. When done, check the file sizes of these tif files. (Note: You can unzip gz files using WinZip as well, but we don’t have WinZip installed on our lab computers.)

5.      You can use the viewer to display individual tif files by changing the file type to TIFF in the “Select Layer to Add” dialog window when loading a raster data layer. Next, we will create a multi-band .img file from these tif files.

6.      Click Import icon on the main icon panel to open the Import/Export tool. Set Type to “Geotiff”, Media to “File”. Click on the file browser icon and go to the folder where the tif files are. Press the control key and use mouse to select XX_nn3, XX_nn4, and XX_nn5.tif. Click on the “Multiple” tab and set the Proxy File to “C:\users\your_workspace\lab2\lab2.vsk” (replace your_workspace with the name of your working folder). When done, click OK.

7.      You will find ERDAS Imagine automatically creates a multi-band virtual stack (.vsk). Now, change the Type to “Virtual Stack (Direct Read)” and select the vsk just created as input. Use the file browser icon to set the output file name (e.g., crestuary.img) so that you can direct the output to your working folder. Click OK to continue. Click OK again on the next dialog window.

8.      Now you created a 3-band image. Band 1, 2, and 3 of the file correspond to TM’s band 3, 4, and 5. Display the image in a viewer using the TM 4-5-3 (R, G, B) band combination, that is, set band 2 to red, band 3 to green, and band 1 to blue.

9.      To help you keep track of the original TM band numbers, you can use the Layer Info tool to rename layer names. Select “Layer Info” from the viewer’s Utility dropdown menu. In the Layer Info window, you can use the “Change Layer Name” function in the Edit menu to change the name of the current layer. You can use the up- or down- arrow or the pull-down list to change the current layer. Change Layer_1 to TM_Band_3, Layer_2 to TM_Band_4, and Layer_3 to TM_Band_5.

10.  Make sure the Layer Info window is the active window and, then, hold down the alt key and press the Print Screen key to screen-capture the picture of the dialog window. Paste the dialog window picture into your MS Word report. Next, screen-capture a blowup view of the estuary of the Columbia River and paste it to your report as well.

11.  Answer the following questions in your report.

Questions:

1.      What are the path and row numbers of the scene that covers the estuary of the Columbia River?

2.      What is the date the TM scene was taken? Hint: check the information in the .met file in the Landsat.org ftp folder. You can use Notepad to open the file.

3.      Why the file size of _nn6.tif.gz is significantly smaller than other .gz files? Why the file sizes of the unzipped tif files are the same? (Hint: What spectral range is TM band 6? What’s its spatial resolution?)

 

Part II. Make Maps from Satellite Imagery in Erdas Imagine

Open the lab book (ERDAS TourGuide9_1.pdf). The lab book (TourGuide9_1.pdf) is in the I:\Students\Instructors\Geoffrey_Duh\ERDAS Imagine folder. For this lab, you will use modeler_output.img to produce a map. You can find the file in I:\Students\Instructors\Geoffrey_Duh\GEOG4581\Lab2. Please copy the file to your working folder and complete the tutorial exercise on pages 79 to 104 of the tour guide.  Produce the map composition in the exercise and put your name on it with a text box. Print the map and hand it in.

Note: Use the following settings to print your map composition.

1.      On the “Printer” tab, set print destination to “ch-469”.

2.      On the “Option” tab, set Image Orientation to “Force No Rotation”.