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MVH Web August 9, 2006 Download WORD doc of this page

Using MVHImage to identify features in a Landsat JPEG

Rita Freuder From a Teachers Workshop, June 2006, Portland, Maine

The students were using MVHImage on the JPEG format of a Landsat 3-band false color image to look at colors within limits defined by a user box. We all made some discoveries. If the box is drawn with the most uniformity of color in mind, it may tell you about landuse in the image. For example, in a false color image, (Landsat bands 4-3-2) a bright light blue is usually concrete, or buildings or other infrastructure.  It turns out that the residential areas and highways are better defined by the blue-grey areas.

Materials: (1 & 2)

1- Right click on this image to download. (http://mvh.sr.unh.edu/mvhinvestigations/images/Portland-ETM2000.jpg)

2- Download MVHImage software. (http://mvh.sr.unh.edu/software/software.htm) Scroll down the page, then chose the type for your system (Mac or PC).

3- Double click the MVHImage application. Use the Select New Image button in the upper left of the screen to load the jpeg file from step 1. It is Portland, Maine - ETM2000.jpg, from an Aug 26 2000 Landsat image.

4- You can define a scale or not. Say none for now. The unit of pixels will work since this jpeg was made from a 512 by 512 pixel data input. So the percent of the image that matches the user-defined box of 3-color bands could be computed in square meters if desired, since one Landsat TM or ETM+ pixel is 28.5 m on a side.

5- Now that you have the image on the screen, try this example:

    A- Analysis Tool: Area

    B- Draw a box within the darkest red color (probably conifers)

To draw a rectangle in MVHImage, click on the mouse for the upperleft corner(it highlights in blue) and drag the cursor. When you release the mouse button, the red dot is the lower right of your box.

 C- Display Tools should be: Set Range of Colors to Show.
(default is RGB when you load your image)

   D- Near the bottom left side of the screen choose: Show Colors within Limits.

 

 A black and white image appears where black represents the pixels that match the range of RGB of those in the box. The white is the unmatched pixels. The percentage of pixels in the whole image that match the box is given at the bottom center.

 

   E- Choose Show Original Image to help clarify what the black area is representing.   

 

F- To draw another box, first choose Display Tools: Red-green-blue, then draw a new box (steps B->E)

Now decide on what other color/landuse you may like to see.  I suggest deep ocean, light pink areas, the cove area, bright blue in urban area, and grey-blue in urban area, and medium red.  I noticed that the sum of all the "color types" did not add up to 100%.  What landuse do you think these boxes represent -- e.g. lakes and rivers, etc.