Processing National Wetlands Inventory (NWI) Data
at 1:24,000 Scale

The following instructions describe how to process NWI data in order to create polygon coverages with NWI attribute information. The procedures outlined were done on a Unix Workstation using the ESRI software products ArcInfo 7.0.1 (herein referred to as "Arc") and ArcView 3.0. The procedures work well for the scale noted above, and for data obtained from the U.S.G.S. website listed below. We cannot guarantee that these instructions will apply to other data scales or data obtained from other sources.
We recommend that anyone using this instructional manual first consult the ArcInfo and ArcView user manuals for additional information on the topics and commands described herein. We accept no responsibility for any problems resulting from the use of this document.

Process 1: Obtain the NWI data

NWI data and related information is available from the following National Fish & Wildlife Service ftp site: ftp://www.nwi.fws.gov
Be sure to read the readme.txt as there is a lot available from this site. The NWI data can be found in the dlgdata/ directory. The NWI data is distributed by 7.5 minute quads. A given quad can be found in a directory named by the 1:250K scale map unit in which the quad is located.
The NWI quad file that you download will be a gzipped, tarred archive file with the .tgz extension. This file will contain the attribute (*.att) and line (*.dlg) files that together make up the NWI data.
Uncompress the downloaded NWI file at the UNIX prompt with the GUNZIP command:
E.G.:
```
	gunzip <quadname>.tgz
```
This produces <quadname>.tar
Untar this file at UNIX prompt with the TAR command, using the flags xvf:
E.G.:
```
	tar xvf (quadname).tar
```
This produces the files <quadname>.dlg and <quadname>.att

Process 2: Convert NWI DLG Data into ArcInfo point, line and polygon coverages

In Arc, set precision to double coordinate precision using PRECISION command:
```
Arc: precision double double
```
In Arc, use the DLGARCcommand to convert the NWI's *.dlg file to an Arc coverage:
```
DLGARC <STANDARD | OPTIONAL> <in_dlg_file> <out_cover> {optional_out_point_cover}

E.G.
	dlgarc optional avenal.dlg avenal_nwic avenal_nwip
```
NOTES:
- The NWI dlg data is in the optional format.
- The "nwic" and "nwip" additions to the output coverage names are conventions for NWI coverage and NWI point coverage.

Build point,line, and polygon topology with the BUILD command.

	Arc: build avenal_nwic line
	Arc: build avenal_nwic poly
	Arc: build avenal_nwip point

NOTE: If build fails or finds intersections, use the clean command.

Process 3: Generate the Attributes for the ArcInfo Coverages

Use a text editor to delete the first line of the NWI attribute (*.att) file. This line is a FORTRAN read statement that is not necessary and will just confuse Arc if left in the file.

In Arc, enter the TABLES subprogram to define an INFO datafile that can be called something like <quad_name>.major. This file will contain the dlg3 major codes and the wetland attributes listed in the NWI <quad_name>.att file.

E.G. (where our NWI quad name is "avenal"):

	Arc: tables
	Enter Command: 	define avenal.major
	      		1
			Item Name: major1
			Item Width: 4
			Item Output Width: 4
			Item Type: I
      			5
			Item Name: attribute
			Item Width: 20
			Item Output Width: 20
			Item Type: C
     			25
			Item Name: <return>
	Enter Command:

Use the Arc-Tables command ADD FROM to select the newly created INFO datafile <quad_name>.major and populate it with values from the <quad_name>.att file.
E.G.:
```
	Enter Command: select avenal.major
	0 Records Selected.
	 
	Enter Command: add from avenal.att
	
```

Use the Arc-Tables list command to make sure that the MAJOR1 codes and attribute values were added successfully from the <quad_name>.att file to the INFO datafile:

E.G.:

 
	Enter Command: 	list
			Record  MAJOR1 ATTRIBUTE
     			1     l   PEMA
		     	2     2   U
     			3     3   PUBHx
     			4     4   PSSA
     			5     5   PFOA
     			6     6   PUBFh
     			7     7   PUSCx
     			8     8   PUSAx
     			9     9   PUBFx
    			10    10   R4SBA
    			11    11   PEMC
    			12    12   PFOAx
    			13    13   R4SBAx
    			14    14   PEMAx
	Enter Command: q stop
	Leaving TABLES...
	Arc:

Process 4: Join the Attributes datafile to the Feature Coverages

In Arc, use the JOINITEM command to attach the wetland attributes to the feature attribute tables of the point, line, and polygon coverages created in Process 2 above. The feature attribute tables (*.pat, *.pcode, *.aat, *.acode, and in some cases, *.xcode) are automatically generated when Arc creates coverages. The DROPITEM command is also used to remove duplicate, uneeded attribute fields.

Care must be taken to type in the filenames correctly.

E.G.:

Arc: joinitem avenal_nwic.pat avenal_nwic.pcode avenal_nwic.pat avenal_nwic-id avenal_nwic-id ordered
Arc: joinitem avenal_nwic.pat avenal.major avenal_nwic.pat major1 major1 ordered
Arc: dropitem avenal_nwic.pat avenal_nwic.pat (!major1,minor1!)
Arc: joinitem avenal_nwic.aat avenal_nwic.acode avenal_nwic.aat avenal_nwic-id avenal_nwic-id ordered
Arc: joinitem avenal_nwic.aat avenal.major avenal_nwic.aat major1 major1 ordered
Arc: dropitem avenal_nwic.aat avenal_nwic.aat (!major1,minor1!)

NOTE: If the coverage doesn't have an .acode file, then go on to do the following, with the .xcode file:

Arc: joinitem avenal_nwip.pat avenal_nwip.xcode avenal_nwip.pat avenal_nwip-id avenal_nwip-id ordered
Arc: joinitem avenal_nwip.pat avenal.major avenal_nwip.pat major1 major1 ordered
Arc: dropitem avenal_nwip.pat avenal_nwip.pat (!major1,minor1!)

SPECIAL NOTE:

Process steps 2, 3, and 4 above have been automated in the AML nwi.aml which can be saved as a file to your local computer and then run from in arc, using the command: &run nwi.aml <quadname>.dlg This AML is available from the FWS ftp-site noted above. We recommend that you read the AML and understand it before running it on your system.

Process 5: Projecting the data (optional)

The processed NWI coverages will have the following coordinate system information: UTM zone #, NAD27. You must use the Arc PROJECT command to change the coordinate system or projection information. In our case, we changed the datum from NAD27 to NAD83 as follows:

	Arc:  project coverage <input_coverage> <output_coverage>

E.G.:
	Arc:  project cov avenal_nwic avenal_nad83 

        project: projection UTM
        project: datum   nad83
        project: zunits  meters
        project: uits   meters
        project: parameters
        project: end

Process 6: Making Shapefiles with ArcView

Open the ArcView 3.0 program
- Click on New View
- Click on Add theme icon
- Scroll to directory with the NWI coverages
- Add the coverages as themes by highlighting them and clicking ok
- Go to Theme menu and select "convert to shapefile"
- Save shapefile with a new name, 8 characters max if you wish to use the coverage on a PC that does not support long file names.
- The *.shp extension will be automatically added so do not give the filename an extension.

This Instruction Manual was prepared by the REGIS group (Research in Environmental Planning and Geographic Information Systems) at the University of California at Berkeley, for the Monterey WATER Project. Further questions can be mailed to: Frankie@regis.berkeley.edu