Directions: Subsetting
 

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Introduction

Using Remote Sensing

  1. Obtaining
  2. Linking
  3. Subsetting
  4. Compositing
  5. False coloring
  6. Ratioing
  7. Supervised classification

Examples

Pre-post test

Directions for Subsetting LANDSAT Images

These directions are needed if you want to limit the size of your file and or the area of interest.
Background requirements: Downloaded and familiarity with the free MultiSpec© software and tutorial (see
http://cobweb.ecn.purdue.edu/~biehl/MultiSpec/Index.html) and a basic understanding of satellite images (i.e. bands, false color imaging, resolution). See A Guide For Teachers http://www.geo.utep.edu/pub/keller/AGuideforTeachers.html

You must have downloaded and linked bands from a terrain corrected LANDSAT 5 or 7 image, and reformatted, renamed and saved them as a .tif file. Refer to the direction sheet titled: Directions For Obtaining Ohio LANDSAT Images and Directions For Linking Ohio LANDSAT Images.

  1. Open MultiSpec©.
  2. Click File.
  3. Click Open Image.
  4. Open the reformatted linked bands image.
  5. Click view. Select Coordinates view.
  6. Change “Lines-Columns” to Lat-Long (Decimal) by clicking on the down arrow in the top menu.
  7. Optional enlargement: The magnification scale is identified in the upper right hand corner of the image menu. A workable magnification is 1:191,339.
  8. Place the pointer of the mouse on the upper left corner of the area on the image you would like to include in a subset of this image.
  9. Click, hold and drag the mouse over the desired area. A rectangle will be created. To redo just reselect your rectangle. It is suggested you include an easily identified landmark such as a mall, river bend or airport. Note the statistics of your selected area are listed at the top of the image. It is suggested that the area selected by less than 4,000,000 pixels, starting with about 400,000 to 600,000 pixels or about 400 –600 sq km. Click on the down arrow in the upper right corner to change the area from pixels to sq kilometers.
  10. Click Processor. Select Reformat. Select Change Image File Format. Click Ok in next screen.
  11. Rename your file with a descriptive name and extension .tif such as: ss Sept 9 05 b1233457.tif