SAMPLE MIDTERM QUESTIONS

Transcription

1 Geography 309 Sample MidTerm Questions Page 1 SAMPLE MIDTERM QUESTIONS Textbook Questions Chapter 1 Questions 4, 5, 6, Chapter 2 Questions 4, 7, 10 Chapter 4 Questions 8, 9 Chapter 10 Questions 1, 4, 7 Chapter 11 Questions 1 Chapter 14 Questions 1, 3, 4 Other Questions Define remote sensing. What are 3 common applications for remote sensing imagery? The City of Regina is planning to build a major multi-modal transportation hub to the west of the airport. This hub will consist of significant rail and road transport infrastructure and associated office and warehouse space. What sensors would provide the data to best suit their needs for planning construction? Why? We have seen during the image presentations in class that there are a lot of very good remote sensing pictures freely available on the web. Why, then, would anyone want to spend $500 or more to purchase a remote sensing image? What are 3 important advantages that remote sensing offers over other methods of data collection? What are 3 significant developments in the history of remote sensing? Why were they significant? What is being sensed by remote sensing instruments? On a sketch of the electromagnetic spectrum label the approximate positions of the following spectral regions: UV, visible blue, visible green, visible red, near IR, thermal IR, microwave (wavelength ranges are not required). What is light? Why do we see objects in different colours? What is a channel on a remotely sensed image? Define spectral reflectance.

2 Geography 309 Sample MidTerm Questions Page 2 What is a spectral reflectance curve? Draw a spectral reflectance curve for healthy green vegetation over the spectral range from blue to near-ir. Label your horizontal axis with the names of the spectral regions covered (e.g., green, near-ir, etc.); label your vertical axis appropriately. Define spectral signature. Describe (what colour is it?) and explain (why is it that colour?) the appearance of healthy green vegetation on a false colour composite image of Regina in summer. Describe (what colour is it?) and explain (why is it that colour?) the appearance of commercial / industrial areas on a true colour composite image of Regina in summer. Which regions of the spectrum show the largest reflectances for vegetation/soil/water? Which of vegetation, soil, and water have the highest and lowest reflectances in the visible portion of the spectrum? What is a fundamental premise upon which much of remote sensing is built? What are 4 types of image resolution that we are concerned about when interpreting remote sensing data? For each resolution type, give one example of an actual resolution value from a common remote sensor. You may use the same or different sensors for each value. What are three factors that determine if an object is big enough to be seen on a remotely sensed image? What is the relationship between the ground sample distance (GSD) at which an image was acquired and the image's spatial resolution? What is radiometric resolution? What effect does radiometric resolution have on remote sensing (i.e., how does changing radiometric resolutions affect image interpretation)? What is the radiometric resolution of the ETM sensor? What is a multispectral scanner? Why are the orbits for resource satellites: a) sun synchronous, b) near polar, c) have a mid-morning equator crossing? What is a geostationary satellite? Are the Landsat satellites geostationary?

3 Geography 309 Sample MidTerm Questions Page 3 If you were in Central America and wanted to take some spectral reflectance measurements on the ground at the same time as a Landsat or SPOT satellite passes overhead, at about what time should you start taking your measurements? Why are the satellites programmed to cross overhead at this time? What type of orbit does a remote sensing satellite have to be in to acquire images of sea ice? Why? Why, when comparing images from different years, it is important to try and have the images coincide on the day and month of acquisition as closely as possible? Identify three major ways in which the SPOT satellite orbits and sensors are similar to those of Landsats 4-7. What are three major innovations that the SPOT system had over the Landsat system (before Landsat 7)? Give one reason why each one is important. What is meant by off-nadir viewing on the SPOT satellite? Identify two major reasons why the off-nadir viewing capability is useful in the acquisition of imagery. Most remote sensing systems can collect data in both a panchromatic and a multispectral mode. What is one advantage of each mode? In order to create a colour composite image, we select 3 bands from a multispectral scene and display one band in red, the second in green, and the third in blue. If you wanted to display a Landsat ETM image, which ETM band numbers would you assign to each colour to create: (a) a true colour composite; and (b) a standard false colour composite? Identify the basic elements of object interpretation and give an example of how they can be used when interpreting a remote sensing image. Why do we analyze images digitally? List some advantages and disadvantages of digital image analysis. What are the 3 basic steps of digital image analysis? List one procedure which is commonly used from each step. Under what conditions do remotely sensed images need to be radiometrically corrected?

4 Geography 309 Sample MidTerm Questions Page 4 Draw a one-dimensional histogram for the following image: PIXELS L I N E S BAND A Why do we need to apply contrast enhancements to remote sensing imagery? List one advantage and one disadvantage of contrast enhancement. Show, with the aid of a diagram, how a linear contrast stretch changes the distribution of pixel values in a histogram. Identify and describe 3 sources of geometric distortions commonly found in remote sensing imagery? Name one resampling method commonly used during geometric correction. List one advantage and one disadvantage of that method. Explain the two steps involved in generating a geometrically corrected image. Which image resampling techniques are commonly used to geometrically correct (a) a classified image; and (b) a reflectance image (i.e., an unclassified image)? What is the difference between a spectral class and an informational class? Give one example of each. On what assumptions do we classify remotely sensed data? Why can we say that an unsupervised classification can never be wrong?

5 Geography 309 Sample MidTerm Questions Page 5 How does this assertion apply, or not, to a supervised classification? What are the steps involved in supervised classification? What are the steps involved in unsupervised classification? What type of classification (supervised or unsupervised) would you be more likely to use: to identify water areas? to update a land use map? to learn more about the types of land covers in a region? to learn more about the types of land uses in a region? if you were in a hurry? if you needed to be sure there were no classification errors? if you needed to be sure you could identify all your classes? Show, with the aid of a diagram, why use of a minimum-distance-to-means classifier is not always a suitable classification procedure to use in image analysis. Identify 3 differences between a supervised and an unsupervised classification. For each difference be sure you state its consequence for both supervised and unsupervised classification. Identify two situations in which you would use an unsupervised classification. During a single-band classification, the computer came across a pixel with a value of 100. Assume the user had defined 3 classes with the following spectral statistics: Class Min Max Mean Std.Dev Into which class would the pixel be placed during: (a) a minimum distance to means classification?

6 Geography 309 Sample MidTerm Questions Page 6 (b) a parallelepiped classification? (c) a maximum likelihood classification? How can you assess the accuracy of a classification? What is a mixed pixel? How do mixed pixels affect the interpretation of an image?