PERFORMANCE ASSIGNMENT                                 NIH 1

Basic Tools: Measuring Distance and Area

Background

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PIA09297: Fractures: Thermal Emission Imaging System on board the
2001 Mars Odyssey, 2007-05-18

The rough and smooth lava flows in this image are part of the extensive flows from Arsia Mons. Image information: VIS instrument. Latitude -20.9N, Longitude 235.2E. 17 meter/pixel resolution.
NIH Image is an image processing program developed by Wayne Rasband at the National Institutes of Health. It was first developed to look at medical images. NIH Imager takes an image defined to be a function of two real variables, for example, a (x,y) with a as the amplitude (e.g. brightness) of the image at that coordinate position (x,y). NIH Image provides for three levels of function:

Image Processing
image in -> image out

Image Analysis
image in -> measurements out

Image Understanding
image in -> high-level description out

Here's a typical screen shot of NIH Image desktop. There are five windows shown here:



    • The color look-up table (LUT) shows what colors are or shades of gray are used in your image.
    • The TOOLS window lets you pick different tools, like a magnifying glass to zoom in on a feature.
    • The MAP window lets you change the brightness and contrast of your image. It's really handy for bringing out detail in washed-out images.
    • The INFO window gives you a readout as you move the mouse over an image. It shows the pixel value, its location, and some other stuff as well.
    • The image window (Valles Marineris in this case - a big canyon on Mars) shows an image that you've opened. You can have several images open at once.

Procedure

Download and Organize Your Materials

    1. Download the NIH Image Program (Scion Image for PCs) HERE to a folder premade called nihimage.

    2. In the nihimage folder, make sure there is a folder called images. If it is not there, make one. Save the image file
        mars.tiff to that image folder by clicking on the image link. The file download popup box will appear, save
        the file to the images folder.

Start NIH Image and Load the Image

    3. Open NIH Image (Scion Image for the PCs) by clicking on the NIH Image icon.

    4. Load the image by selecting the File dropdown menu and clicking on Open. Navigate to the images folder
        and select the file: mars.tiff. You may need to move the five windows arounds so that you can see them.

Scale the Image

    5. Select the magic wand tool from the tool window. Measure a prominent landform such as a crater rim, by placing the mouse on the left side of the rim, depressing the mouse button, dragging the mouse acr oss the diameter of the crater rim and releasing the mouse button.

    6. Select the Analyze dropdown menu and click on Set Scale. A dialog box will appear.


         Notice that the top line in the dialog box has the "Measured Distance" in number of pixels of the straight line
        segment corresponding to the diameter of the crater rim. First, change the units to "meters" in the "Units:" box.
        Now compute the length of the line in meters. Do this by multiplying the "Measured Distance" in pixels (23.00 in
        our example) by the resolution in meters/pixels, 17. Click OK to set the scale.

Analyze