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I have a land cover classification derived from Landsat TM imagery - I created this classification using ENVI. I would like to edit individual and groups of cells in some areas of the classification in order to improve the accuracy of the output by comparing it with aerial imagery.

Is there a way, using ENVI or ArcGIS, to manually edit large groups of cells by selecting them and assigning them to a new or existing class? I am aware of merging methods based on class statistics, but the area I'm classifying has a high amount of spectral confusion due to thin cloud cover - it seems like a manual edit is the only way to go.

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Have you considered running atmospheric correction on the base image, such as dark body subtraction? –  Aaron Nov 13 '12 at 13:24

3 Answers 3

up vote 7 down vote accepted

I don't think there's a really simple way to do this, but one way would be to:
Create a new polygon layer and create polygons over the areas you want to change the values of.
Code the polygons with the desired land cover value.
Convert the shapefile to a raster.
Use the Raster Calculator to substitute the new values.

Con(("POLYRAST" > 0),"POLYRAST","CLASSIFIED")

That's about the simplest way I can think of. :-/

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That's a decently simple solution - I can just digitize polygons over the aerial imagery and follow the steps you outlined. I wish there was a way to do it simply like MSPaint for rasters, but as far as I know MSPaint doesn't support Geotiffs :$ –  Nick Ochoski May 9 '12 at 23:10
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@radar, it's possible to use any graphics program that understands regular tiffs: 1) save georeferencing, 2) paint image -- being careful not to change dimensions, or using colour values outside the valid data range, 3) save, 4) restore georeferencing from #1. This work flow is worth a new question on it's own; the closest answer I see so far is gis.stackexchange.com/a/24798/108, while the subject for this Q gis.stackexchange.com/questions/76572/touch-up-tool-for-rasters is perfect (body is a bit too specific). –  matt wilkie Mar 7 at 23:01
    
Thanks forestman - your "Con" statement just saved me a bit of time, and I learned a new little trick. Much appreciated. I 1 upped you!! –  dklassen Apr 4 at 22:40

If your imagery is in ESRI GRID format the editing can be done with the ARIS GRID Editor for ArcGIS: www.aris.nl/grideditor_arcmap

The ARIS GRID Editor adds a toolbar to ArcMap. This toolbar provides a set of tools to change the value of one or more cells. With these tools it is possible to:

  • change the value of a single cell or pixel (pencil)
  • draw a free line (pencil)
  • draw straight lines from one point to another (line)
  • draw a solid polygon (polygon)
  • set pen size in cells to be affected while drawing
  • change the value/color of a zone of cells with identical values (paintcan)
  • recover the original value of individual cells (eraser)
  • replace one value with another value in the entire grid (value replacer)
  • create a selection area in the map to limit the working area for the above operations (edit area)

Available as 5-day free trial. Current pricing is 320 Euro.

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Very nice, but rather expensive. –  nadya Nov 13 '12 at 22:49

I've used arcscan and the paint tool to edit individual pixels but this was on a grid which had only 2 values for pixels.

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