Introduction to Environmental Remote Sensing
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Frequently asked questions
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a. Lab hours, lab access, etc.
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1. Where can I use ENVI in Science Hall?
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Since you do not have access to room 380 after hours, you can use ENVI on any of the public computers in Science Hall. These include:
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The Geography Library - for hours, location, http://geography.library.wisc.edu/
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The Map Library - for hours, location, http://www.geography.wisc.edu/maplib/loc_hour.html
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The M376 Lab
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2. Are there other labs on campus that have ENVI?
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Yes. Please check out the Forest and Wildlife Ecology lab in A120. The lab hours are posted on the door of the lab. Forestry sets the schedule for that lab so the availability may change due to meetings and lectures.
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b. Lab questions
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1. For the Introduction to ENVI lab, I'm a bit hung up on the first question and what exactly constitutes 'discriminating'. In order to "discriminate a feature" should a band portray it in black? Or white? Or in the band that offers the most contrast between the feature and its surroundings? Or that offers the least variation within the areas classified as containing said feature?
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Start by making a quick list of land cover types or features that you would like to be able to see in a given scene. Then for each, look for the band that helps you differentiate that feature from others -- it is likely that contrast is going to be the most important thing here. Try to find which band helps you see this feature the best.
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Also take a look at Jensen's Remote Sensing of Environment page 205. There is a nice table on the utility of certain wavelengths to discriminate features. Just remember that we used Landsat bands 1-5 and 7 in lab (you did not view the thermal band, band 6).
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2. I am having some trouble with my classification. Highly reflective areas such as urban areas and bare fields are confused in the classification results. Should I redo the map?
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There is no need to make the most accurate maps at this point. Remember, the point of this exercise is for you to learn the process, understand your results and determine what may have gone wrong, and explore ways to fix these issues. In future labs, we will explore ways to fix some of these problems, but for now, you will describe and assess the problems in your lab write-up. You may also wish to highlight the area where you are having trouble by zooming in and taking a snapshot, and then including this as a figure in the write-up.
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c. ENVI technical questions
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1. I'm having trouble retrieving my class statistics. What should I do?
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Your stats need to come from your saved ROIs to do this
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Open the original Landsat image
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Restore your ROI's from the file you saved them to
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Run the stats for all the ROI's as per lab handout
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Save the stats as text (for import into Excel)
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Conduct analysis of data in Excel
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2. I am having trouble getting my ROI's to show up on the scatter plots. What should I do?
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Have you saved the ROI's? Then, in the scatter plot dialogue box, go to:
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File > Import ROIs
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They should now appear in your scatter plot and on your image.
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d. General lab write-up questions
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1. Can I turn in my lab if I miss lab time?
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Yes, please hand it in to your T.A.’s mailbox.
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2. The size of my pdf file is over 30 mb and I cannot email it. What should I do?
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Please reduce your jpg images to reduce the size of you document and resend it via email. One option would be to open the files in a graphics program and then save them as a lower resolution or a smaller physical size.
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3. If I attend another lab section, when is my lab due?
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No matter what session you attend, your lab will be due at the beginning of the lab period for the lab section for which you are officially registered. You may always hand it in early if you attend a session earlier in the week.
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