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Thursday, 12 July 2012

Image analysis: Reclassify the pixels of an Image


To reclassify an image into classes could be useful when we need to investigate what is going on inside the cloud of pixels. At this time I am sharing an example on how to do that using Arcmap. The example shows the next step on the NDVI analysis presented in the previous post Acknowledgments are for Buitron and Fernandez (2102), and the copyrights statement is shown on the bottom of the page.

  • Go to ARCMAP, and open the image you wich to reclassify (ex. l520030830_ndvi.img).
  • Right click→Properties. The window “LayerProperties”pops up.
  • There, go to the tab Symbology→Classified→Clasification.
  • Go to ClassificationMethod
  • Look for the option Manual
  • In Classes write 4.
  • In Break Values write the ranges we want (ex. for the case of the figure below, it has been carried a NDVI analysis, where have been used the ranges 0,2 ; 0,35; 0,5  until 1)
  • OK.
  • On the window “Layer Properties” you will be able to observe the changes that have been made. You can also change the color of the legend
  • Accept.
  • Go to ArcToolbox Spatial Analyst Tools Reclass Reclassify. 
  • In Input Raster look for the image, ex. l520030830_ndvi.img, which will be reclassified.
  • Click on “Change Missing Values to Not Data”
  • OK.

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