Directions: Ratioing
 

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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 making band ratios from LANDSAT images 

These directions can be used after data has been downloaded and linked and at least one image as been subsetted. Ratioing helps identify land cover types. Notice in figure 1 that the slope of the line connecting red and near infrared reflectance is greater for the cotton than bare soil, than any other band combination. By dividing these two bands (slope of line) the vegetation/bare soil surface cover is accentuated and other conditions such as lighting and surface slope is minimized.
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 is helpful (i.e. bands, false color imaging, resolution).

Refer to the direction sheets titled: Directions For Obtaining Ohio LANDSAT Images, Directions for linking LANDSAT single band images, and Directions for Subsetting Single Images of LANDSAT images.

  1. Open MultiSpec©.
  2. Click File. Click Open Image. Select the file of linked bands you want to ratio.
  3. Select Processor.
  4. Select Reformat.
  5. Select Change Image File Format.
  6. Select Transform Data.
  7. Select New Channel from General Algebraic Transformation.
  8. Change numerator to C4 and Denominator to C3 and multiplier (X) to 255.
  9. Click OK.
  10. Click OK in next window.
  11. Save image as a .tif file with a new name such as ratio b4db3 may 00.tif
  12. Close initial file and open newly saved ratio file.
  13. Select:  Display type 1-channel grayscale. Click OK.
  14. Zoom in and re-center as needed.