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I've been working with NLCD data at a county level. My goal is to reclassify the pixels that fall under the open water classification. I've got a hydrography shapefile for the same geographic location so I can compare and areas and see what the open water actually classifies as, whether it's river, lake etc. Is there an easy tool to reclassify these based on the hydrography. For some reason I'm drawing a blank on the most efficient way to do this? Pretty much I want to take the open water cells from my raster and change them from open water to river lake or whatever based on what the hydrography attribute table says.

NLCD : National Land Cover Database. It's published by the USGS every five years in raster format 30x30m pixels. Each pixel is classified by a number which corresponds to a legend representing ladncover type. For instance, any pixel that is classified as 11 means open water. So basically I want to classify all the 11 pixels more in depth to indicate whether they are a lake, river or actually open water since I am looking at an area around the puget sound

  • What's NLCD? I think you should write that out in full the first time that you use the term in a question here. – PolyGeo Dec 9 '15 at 22:49
  • Sorry, it stands for national land cover data. It's published by the USGS every five years in raster format 30x30m pixels. Each pixel is classified by a number which corresponds to a legend representing ladncover type. For instance, any pixel that is classified as 11 means open water. So basically I want to classify all the 11 pixels more in depth to indicate whether they are a lake, river or actually open water since I am looking at an area around the puget sound. – T. Volz Dec 9 '15 at 23:05
  • There's an edit button beneath your question that you can use to revise it with any requested clarifications such as this. Also, as someone new to the site you should take the Tour to learn about our focussed Q&A format that is quite different to discussion forums and any other Q&A sites you may have worked with. – PolyGeo Dec 9 '15 at 23:12
  • Regardless of the workflow you end up using, you may very well need to come up with some sort of rule set for how to deal with Open Water pixels that are not coincident with your hydrography. The NLCD has a classification accuracy of ~80% (for 2001). You may run into issues specifically where vector representations of rivers do not capture the true width of that water feature. – Lovette Feb 8 '18 at 15:09
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Check into features to raster, overlay, and raster calculator functions. For example, if you convert the features to raster you could use the output raster (containing values for lake, river, or open water) as a mask to determine which cells to change, and use the raster calculator to convert the values as needed.

Here are a couple of resources I found related to the Raster Calculator in ArcGIS (requires Spatial Analyst license) and QGIS.

This question may also be helpful as it seems similar and has a more detailed answer.

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