Part 1—Download Software and Data

Step 1 Download and Install ImageJ Software

ImageJ is in the public domain. It can be freely downloaded and installed on any computer including those at schools, homes, and businesses.
  1. Go to the ImageJ Download page and open it in a new window.
  2. Click the link that appears directly below the name of your computer's operating system (e.g., Mac, Linux, Windows). This action will transfer a compressed file of the software to your computer. Your browser should automatically expand the file, creating an ImageJ folder on your computer's hard drive.
  3. For more detailed instructions from the ImageJ website, click Installation Instructions, then select your operating system.

Note to Windows Users: It is recommended that you install ImageJ in the Documents directory, rather than in the Program Files directory. For security reasons, Windows 7 and Windows Vista do not allow programs to alter themselves by writing files to the Program Files directory. If ImageJ is installed in the Program Files directory, then the update function in Step 2 below will not work properly. In addition, if you are a Windows Vista user, be sure to choose the correct version of ImageJ (either 32-bit or 64-bit) for your computer.

Step 2 Update or Downgrade ImageJ

ImageJ Updater Window ImageJ update dialog box.

Double-click the ImageJ icon ImageJ Icon Small to launch the application and choose Help > Update > ImageJ.... A window will appear, telling you the version you are currently running and a list of upgrade versions. Choose the version you want to upgrade to (usually the most recent, or default version) and click OK. After the update downloads, you will need to re-launch ImageJ to run the new version.


ImageJ Updater Window Options ImageJ update dialog box showing upgrade and downgrade options.

ImageJ is a professional research and analysis tool, and is under constant development. If the latest update of the application introduces new bugs or errors, or has an unfamiliar interface that does not match written instructions, you can downgrade your copy of ImageJ to an older, more stable or familiar version.

Step 3 Download Sea Ice Data from the National Snow and Ice Data Center (NSIDC)

  1. Download Sea Ice Data for the Arctic from the years 1978-2006 from the NSIDC website as a "tar" or compressed file. Click the Monthly Sea Ice data sets link to download the images in monthly order. Your computer will ask you what to do with the file. Simply save it to your downloads or desktop folder. Do not try to open it at this point in the lesson.

    A .tar file is a compressed file. Later in the lesson you will be instructed how to open it. To learn more about this type of file read this Wikipedia article.
  2. A new window will open and the download will be ready to begin. A dialog box will ask you where to save the data.

    save-tar-file_small
  3. Create a new folder for all of the data and products of this exercise. Store it in a place you can access easily such as on your desktop or in your documents folder. The file that you are downloading is about 45 mb so it may take several minutes to download.
  4. If you have difficulty with the .tar files you can try the zipped folder attached to this site. While our goal is for you to be able to download and analyze whichever Sea Ice images you want directly from the NSIDC site, we're offering another link to the necessary images so you can work through the analysis technique presented in this activity.

    Download a compressed file that contains the sea ice images
    • Right-click (ctrl-click on Macs) this link to monthly.zip (Zip Archive 10.3MB Aug16 12) If you have limited memory choose quarterly.zip ( 2.8MB Nov22 07) (an even smaller file - 2.8mb, only has the files from months 3,6,9 and 12).
      Choose the "Download Link to Disk" or "Save Link As..." option.
    • Once the file downloads, you may need to double-click it to decompress it. The decompressed file will be a folder named monthly or quarterly.
    • On most computers, simply double-clicking - the file will launch your decompression software.

    The NSIDC Sea Ice Index is a collection of summary data and browse imagery of monthly sea ice conditions. It is derived from raw data fields produced for one of NSIDC's products: "Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data"

    To download the data:
    1. Go to the website http://nsidc.org/data/nsidc-0051.html
    2. Click on the "Access Data" button. You will be asked to fill out a User Registration Form, though this can be bypassed with a link in the upper right-hand corner of the page.
    3. There are three directories, each for different time periods.
    4. Most of the data, the oldest data, are in "final-gsfc", more recent data from the end of the "final-gsfc" through ~3-6 months ago are in "preliminary", and the most recent data (the last 3-6 months) are in "near-real-time". The data in the "final-gsfc" folder was processed by scientists at the Goddard space flight center.
    5. Click on the "final-gsfc' folder to select it.
    6. Within each directory, are subfolders by hemisphere and then by "daily" and "monthly." It will generally be easiest to work with monthly data. The time of each field is in the filename with the 4-digit year immediately followed by the 2-digit month (and then immediately followed by the 2-digit day of month for the daily data).
    7. Select from the list of files and download by right-clicking on the name of the file and saving it to your desktop.
  5. Once the download is complete and the file is decompressed, you can check to see if you have the full dataset. Open the folder named pub and keep opening all the embedded folders until you have opened the monthly folder (buried 7 levels down). NOTE: Do not open these files, merely check that they are available.
    Recent versions of operating system software can recognize and decompress .tar files. Once it is downloaded, the .tar file may decompress automatically, or you may need to double-click on the file's icon to begin the process. If the computer you are using won't automatically decompress the file, check for decompression software on your computer. Launch the software, choose the option to decompress or "unzip" a file, then browse to where the compressed file is stored. If necessary, use an Internet search engine to search for "decompression software" for your computer. Two popular packages that are available are WinZip (PC) or StuffIt (Mac).
  6. Familiarize yourself with the dates of each image from the file names. The first 4 digits indicate the year and next 2 digits tell the month. The "n" at the end of the file name indicates north. Scroll through the files and you will see that they are from 1978- present (2010). The first file name is nt_197810_f07_v01_n.bin. It represents sea ice concentration from October, 1978.

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