Part 2: Present Your Research

On Day 4, you began a simulated research project. The first step was to become familiar with the datasets, then you pre-processed some of the images and created a set of ROIs (Regions Of Interest) for your study areas. Today you'll use these ROIs to identify and measure monthly sea ice coverage data for each study area. The directions for this session will be less detailed than previous sessions—if necessary, return to previous exercises to review detailed instructions. Note: This WILL take both practice and patience, as well as trial and error to find out what works best for you without compromising the quality of your data. If these techniques don't work perfectly for you, read the directions again, then improvise.

Complete Pre-Processing

Before you begin data collection, download these additional sea ice images, import them into ImageJ, and save them in TIFF format. If you don't remember the import settings, see Day 4 Part 2.

• Arctic Sea Ice 1979 March (Zip Archive 50kB Jul22 11)
• Arctic Sea Ice 1979 Sept (Zip Archive 30kB Jul22 11) *This was the file you used yesterday, so you should already have it.
• Arctic Sea Ice 2006 March (Zip Archive 45kB Jul22 11)
• Arctic Sea Ice 2006 Sept (Zip Archive 30kB Jul22 11)
• Arctic Sea Ice 2007 March (Zip Archive 45kB Jul22 11)
• Arctic Sea Ice 2007 Sept (Zip Archive 26kB Jul22 11)

Open these images from Day 4 in ImageJ. If any of them are missing or incomplete, return to Day 4 to complete them before continuing.

• Arctic_2007September sea ice image (from Day 4), saved in TIFF format.
• Arctic_Pixel_Area image (from Day 4) saved in TIFF format.
• Arctic_ROI.zip file containing four (or more) carefully-made ROIs of your selected study areas. ROI Manager for your selected study areas.

Identify Sea Ice Extent for September 2007

The working definition of sea ice extent is that it includes all pixels with 15% or greater sea ice coverage.

• Activate the Arctic_2007September image and use thresholding to highlight the pixels with values of 150 to 1000. This corresponds to 15–100% ice coverage. (Hint: Click the Set button and enter the min and max threshold values.)
  
  Show me the threshold settings
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• Convert the threshold area into an ROI (Edit > Selection > Create Selection, add it to the ROI Manager, and name it Sep2007.

Measure Sea Ice Coverage For Your Study Areas

All your ducks are in a row—now you can start making measurements of the sea ice coverage for each of your study areas!

• Choose Analyze > Set Measurements and turn off all of the measurements except Integrated Density and Display Label. Set an appropriate number of decimal places for your answer.
• Activate the Arctic_Pixel_Area image.
• In the ROI Manager, click the Sep2007 ROI then control-click (PC) or command-click (Mac) the Arctic Ocean ROI (that's the one everyone should have done on Day 4). When you click the second ROI, the More menu should automatically pop up.
• Choose the AND operation from the More menu.
Show me what it should look like just before I click AND
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The AND operation creates a new ROI that is the intersection between the selected ROIs. This ROI represents the sea ice coverage IN the Arctic Ocean study area. You may add the new selection to the ROI Manager, but it is not required.


CAUTION – Select None = Select All! If the sea ice extent and study area ROIs don't intersect, nothing is selected. Remember, in ImageJ no pixels selected is treated the same way as ALL pixels selected. In this example, measurement 3 is the area represented by the entire image!





• Choose Analyze > Measure to measure the area of the sea ice in the Arctic Ocean study region for September 2007.
  Show me the ROI and measured area
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• Continue this process of "intersect and measure" for each of your study areas.
  Show me the results for all study areas for September 2007 (no peeking!)
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  Arctic Sea Ice Areas for September 2007

  Note that measurements 2 and 6 (Gulf of St. Lawrence and Sea of Okhotsk) show the area of the entire image. These results should be interpreted as no sea ice coverage. All measurements are in square meters. To convert to square kilometers, divide areas by 1,000,000. Your results will not match these exactly, but they should be close.
  
  

  

  
  

  Part 2 Assignment

  1. Repeat these measurements for at least 2 additional months for each of your selected study areas.
  2. If possible, transfer your measurements to a spreadsheet. (See Graph the Results on this page from the Introduction to Analysis workshop for instructions.)
  3. Go to the Part 2: Share and Discuss page and post a screen shot of your Results window or spreadsheet, along with a brief discussion of what you learned from the data and/or the process used to collect it. Where might errors have occurred in the process and what steps could you take to avoid or correct those errors.
  4. Share a brief outline of an investigation you might have your students carry out using image analysis techniques you learned during the advanced image analysis course, then engage in an online discussion, sharing and comparing ideas with colleagues.

  Source

  ¹Adapted from Earth Exploration Toolbook chapter instructions, "Whither Arctic Sea Ice?" under Creative Commons license Attribution-NonCommercial-ShareAlike 1.0.
  ²Adapted from Eyes in the Sky II online course materials, Copyright 2010, TERC. All rights reserved.
  ³New material developed for Earth Analysis Techniques, Copyright 2011, TERC. All rights reserved.