Lab 1: Intro to Remote Sensing Concepts and ERDAS Imagine

Geog 477-Lab1 Due September 4, 2007

Lab 1: Intro to Remote Sensing Concepts and ERDAS Imagine

Part I: Remote Sensing Concepts

1. Represent the base-10 number 175 in base 2.

2. Represent the base-2 number 10010111 in base 10.

3. Represent the base-4 number 3121 in base 10.

4. Represent the base-10 number 93 in base 4.

5. What would be the dynamic range of a sensor that coded each pixel value using a 12-bit byte?

6. Calculate the frequency of radiant energy at wavelengths of 0.4μm and 0.6μm.

7. What is the wavelength of 91.5 FM (WUNC) (91,500,000 Hz)

8. Calculate the total energy emitted by blackbody emitters at the following temperatures: 6000K (Sun), 4000K, 3000K, 2000K, 1000K, 600K (Venus), 300K (Earth) and 100K (Jupiter). Plot the total energy as a function of temperature on a graph.

9. Calculate the wavelength of maximum emittance for the objects at the above temperatures. Plot the wavelengths as a function of temperature.

10. Consider a sensor for which the continuous response of the detector elements is integrated (sampled) every 10μs in order to produce 50m spatial resolution data. The width of the scan in the across-track direction is 120km. If we assume that a scene is 100km long in the along-track direction, how long will it take for the sensor to sample an entire scene? How long will it take to sample a single scan?

11. For the sensor above, assuming it samples the surface in three spectral bands and has an 8-bit dynamic range, what will be the data volume of a single scene? Give your answer in megabytes.

12. Read the Current Stories section of http://earthobservatory.nasa.gov/ and write a 1 paragraph synopsis on a story of particular interest to you. The paragraph must describe the following elements in a maximum of 2 sentences each: 1) the research question; 2) methods used; 3) results found; and 4) the implications of the research.

13. Figure 1 illustrates the spectral signatures of different surface materials extracted from a Landsat Enhanced Thematic Mapper (ETM+) image for central New Mexico. The wavelength range of each spectral band of the Landsat ETM+ sensor is listed as follows:

Geog 477-Lab1 Due September 4, 2007

Band 1 0.45-0.52μm (Blue),

Band 2 0.53-0.61μm (Green),

Band 3 0.63-0.69μm (Red),

Band 4 0.78-0.90μm (NIR),

Band 5 1.55-1.75μm (SWIR),

Band 7 2.09-2.35μm (SWIR),

Band 6 10.40-12.50μm,

Band 8 0.50-0.90mm

Geog 477-Lab1 Due September 4, 2007

Bands 6 and 8 are not plotted on the graph.

(a) Based on the graph below, which region of the spectrum shows the greatest reflectance for (1) grasslands; (2) conifers; (3) dark soil; (4) light soil; and (5) NPV (non-photosynthetic vegetation)?

(b) Which two bands appear most useful for distinguishing among these five classes?

(d) Which two classes appear least distinguishable?

(e) Which two classes appear most distinguishable?

(f) Identify three major differences between band 6 and the six spectral bands used to produce the signatures shown below?

(g) What are two major differences between band 8 and the six spectral bands used to produce the signatures below?

Figure 1 Spectral signatures of 5 surface materials extracted from a Landsat ETM+ image for central New Mexico.

Part II: Getting to Know ERDAS Imagine

(1) Directories

Note that the data directory and student directory for this course are located at:

/afs/isis/html/courses/2007fall/geog/477/001/Data

/afs/isis/html/courses/2007fall/geog/477/001/studentsa-j and …/studentsk-z

The location …/Data is the directory from which you will copy files for the lab assignments. So, within this directory you will find files that you can copy to your own working directory. Under …/studentsa-jor …/studentsk-z there is a subdirectory for each of you. For example, if your ONYEN is jones, then your own directory is …/studentsa-j/jones.

· Create a Lab1 folder in your own directory and copy uncimage.img and subset.aoi from /afs/isis/html/courses/2006fall/geog/477/001/Data to that folder.

· To create a shortcut to your directory click on the AFS lock icon in the lower right hand corner of your desktop. Click on Add…and select a drive letterfrom the pull down list (for example, F:) and enter to following as the AFS path (make sure “restore this mapping whenever I logon” is checked):

afs\isis\html\courses\2006fall\geog\477\001\studentsa-j or studentsk-z\onyen

(2) Starting ERDAS Imagine

· Start ERDAS Imagine by selecting Start | Programs | GIS Applications | Leica Geosystems | ERDAS Imagine. A toolbar and an image viewer will appear on the screen. Click OK for a Classic Viewer. Look over the tool bar for a couple of minutes.

· You can tell Imagine to go directly to your work space every time you load a file by selecting Session | Preferences… Make sure User & Interface Session is highlighted in the preference editor. Now enter F:/ for the Default Data Directory and the Default Output Directory. Click on User Save and then close the preference editor. Now anytime you open or save a file you should be automatically redirected to your work space on AFS. This will save you a ton of time!

(3) Viewing a raster image in Imagine

· Viewer # 1 should automatically open at Imagine startup (if the Viewer is closed, click on the Viewer Icon on the Imagine toolbar to open one). Go to File, select Open, and then select Raster Layer. Double click on uncimage.img after navigating your way to your work directory and the image should appear on the viewer screen. Click Yes to pyramid layers

· Spend some time exploring the viewer toolbar.

· Pan and zoom the viewer to find the UNC campus.

15. What are the UTM coordinates for the Dean Dome? For Saunders Hall?

(4) Subsetting an image using an Area of Interest (AOI)

· This lab will focus on the area directly surrounding the campus. Thus you will create a subset of the image that includes only this area of interest (AOI). Go to DataPrep | Subset Image in the Imagine toolbar. Navigate to your working directory by clicking on the folder icon next to the input file box. Select uncimage.img as your input file and name uncsubset.img as your output file (be sure to save to your working directory). You can select map coordinates for the corners of an AOI but for the purposes of this lab, you will be provided with specified AOI coordinates. Click on AOI… at the bottom of the subset box to load the predetermined AOI file. Check AOI file and select subset.aoi from the data folder (/afs/isis/html/courses/2006fall/geog/477/001/Data). Click OK. The process of generating this subset may take a few moments. Open uncsubset.img in a new viewer.

16. What are the different file sizes of the original and the subset UNC images? Why is this important?

(5) Changing the spectral band combinations for an image

· In the viewer, select Raster | Band Combinations…You will see a default color combination for bands 4, 2, and 1 (assigned to the red, green, and blue, color planes respectively). This color combination can be changed using the up and down arrows next to the band (layer) number to emphasize a range of landscape features. Make sure the Auto Apply box is checked and explore different combinations of red, green, and blue for all of the band numbers.

17. Which band combination appears the most “realistic”?

18. Which combination would cause the campus to appear Carolina blue? What color is the baseball diamond using this combination?

19. Which combination would cause the forest to appear Duke blue? What color are the buildings on campus using this combination?

20. What happens when you select band 2 for red, green, and blue? Why?

(6) Spectral signatures of different land cover types

· Select from the viewer toolbar. Click OK for spectral signature. Select the cross button and click on a point in the viewer to create a spectral signature for that pixel.

21. Create a chart depicting the spectral signatures of forest, buildings, water, and Astroturf using the spectral profile tool. Scale and label your chart so that you can see separation of the signatures on the y-axis. To do this, go under Edit | Chart Options… and Edit| Chart Legend… Include the chart of spectral signatures in your lab report using the print screen and paste functions.

22. Create a spectral signature for the forested area southwest of the Dean Dome and one for the forest southeast of the Dean Dome. Why do the two signatures appear so different in Band 4? Hint: you could go there and look for yourself!

Delete uncimage.img from your working directory to conserve disk space.

When you quit Imagine, don’t print the log file!

The ERDAS Tour Guide is a useful resource for information on the software:

J:\isis\pc-pkg\imagine-86\program\help\hardcopy\TourGuide.pdf

What should be saved in your working directory?

Your completed lab assignments should be saved to your directory as onyen_lab#.doc by noon on the day that they are due. We will not accept paper labs.

Note that there are limits to available disk space. Please keep your directories clear of redundant and/or unnecessary files.