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I have sample points in an Excel file with XY coordinates and canopy density. I also have a Landsat ETM+ image. All points are collected from the same area as in the image.

  1. I exported all sample points by first ‘Display XY data’ and then ‘Export data’, thus I got a shapefile.
  2. I used "Sample" extracted all points from ETM+ image, then I got a table and exported it to a DBF file. In the DBF file I have XY coordinates for all sample points and band values.
  3. Then I copied all band values from DBF to original sample points Excel file, then I calculated NDVI and did linear regression (canopy density as dependent variable and NDVI as independent variable) in Excel. Therefore I got a regression equation.
  4. After added the Excel to ArcGIS and joined it to sample points shapefile, I carried out OLS. However, I only got all sample points regressed.

What could be the problem and how should I apply regression equation to the image so I can produce a map?

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you should apply your regression equation to your NDVI image using the raster calculator (map algebra tool)

"ndvi_raster" * slope + offset

where slope and offset are the numerical values of the parameters of your regression

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