Hi,Jonathan:
Would you please tell me how i can find the meaning of the categories of NWI ? I need a link to know all of these stuffs, you know i dont have any background of this field, thank you very much
Please start with the technical documentation, especially table 5, and the reference shown below that table.
Other resources include:
http://www.fws.gov/wetlands/Data/WetlandCodes.html
http://wetlandsfws.er.usgs.gov/nwi/decoder/decoder.aspx
http://www.fws.gov/wetlands/_documents/gNSDI/ClassificationWetlandsDeepwaterHabitatsUS.pdf
Good luck! -- J