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Started by kij4, February 12, 2017, 10:43:44 AM

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I was just wondering how you incorporate NWI codes into SLAMM, I am a beginner with SLAMM and computer codes in general, I am struggling with the incorporating of the NWI codes. I have got a friend who has helped with the conversion of slope and DEM data but we are both stuck on the NWI codes!

I got the main bulk of my dem and aerial imagery from earth explorer and has been manipulated in arcmap, and exported! I am just struggling with the NWI, any advice or help will do!

Many thanks,

Jonathan S. Clough

Hello.  The steps are basically as follows:

1. Get the NWI shape-file
2. Add an integer field to the NWI dbf file called SLAMMCODE for ecample
3. Use the latest xls crosswalk to fill in the fields of the SLAMMCODE based on the NWI code
4. Convert the shapefile to raster using the SLAMMCODE as the basis
5. Always QA/QC and ground-truth the conversion.  The NWI is not perfect, the crosswalk is not perfect and sometimes there is ambiguity between Cowardin classes and SLAMM codes.

Now, we can and have provided additional assistance on individual steps, so let us know if and when you are getting stuck.

Also, see this thread:


Thank you!

I got it working in the end, I followed the steps on the other thread but wasn't working. My friend got it working after noticing the file wasn't exporting properly!

Thank you for your assistance though.


i got 2 queries,
1. how to produce NWI data ( i was looking for a more clear answer as i am not that expert in GIS)?
2. If I use ASTER GDEM data other than LiDAR, will I face any problem with my result?

Jonathan S. Clough

NWI is a product of considerable technical expertise from US FWS that includes satellite data, infrared photography data, photographic interpretation, and considerable GIS expertise.

You do not need an NWI data set to use SLAMM however.  You do need some sort of high-quality vegetation land-cover polygons that can be cross-referenced to the SLAMM categories.