Process Description:
To improve the performance of the web applications displaying the 2007 wetlands data, it was necessary to create a new simplified layer that included only the minimum number of polygons and attributes needed to represent the 2007 wetland conditions. This new layer, WET07, was created using the following steps: The existing statewide integrated 2007 land use geo-database layer, which includes the 2007 wetlands polygons and codes, was first converted to a polygon coverage. This was done because the processing steps needed to simplify the polygons and retain the needed attribute items in the separate output layer can be more directly done using a coverage than a geo-database layer. This coverage was named LULCFULL. Once the coverage was created, several new attributes were added to the polygon attribute table (.pat) to facilitate further processing. First, a new field, LU07INT, was added to replace the original field, LU07, which holds the land use code values. These code values are only four digit integers, but the conversion process from the feature class to the coverage results in LU07 being defined as a floating point attribute in the output coverage. LU07INT is correctly defined as an integer field with width 4. LU07INT is then calculated to equal LU07. The conversion process also causes the original impervious surface field, IS07, to be defined as a floating point attribute in the output coverage, which complicates further processing. A new field, IS07INT, defined as an integer field with width 3, was added and evaluated by calculating IS07INT = IS07. The impervious surface values could now be further simplified to a two digit impervious surface category using a look-up table and the ARCINFO JOINTIEM command. Since the impervious surface values are given in 5% increments starting at 0 and ending with 100%, there are 21 possible impervious surface values in the coverage,. The look-up table created had two fields IS07INTand IS07CAT. IS07INT was defined as described above and populated with the original impervious surface percentage values. IS07CAT was defined as a two digit integer field and evaluated from 1 to 21, with an IS07CAT value of 1 representing an IS value of 0, an IS07CAT value of 2 representing an IS value of 5, etc,. The JOINTEM command was as follows: JOINTEM LU07.PAT IS07CAT LU07.PAT LU07INT LU07 With the two new integer fields created and evaluated, the land use code and the impervious surface value for each polygon for 2007 could be represented by a single 6 digit integer attribute, ISLU07, created from concatenating the two new fields into a new attribute. This was down in INFO using the expression CONCATENATE ISLU07 FROM IS07CAT,LUO2INT. Once the concatenated field was evaluated, a new simplified 2007 land use layer was created by dissolving on ISLU07, using the ARCINFO command DISSOLVE LULCFULL LULC07 ISLU07. Since the output coverages from the dissolve processes only include the dissolve item, ISLU07, several additional steps were required to fully populate the dissolved coverage with all the attributes needed to fully define the land use characteristics of each polygon remaining in the coverage LULC07. First, the field ISLU07 was converted into two separate virtual fields using the INFO command REDEFINE. IS07CAT was redefined as the first two digits of ISLU07 and LULC07 was redefined as the next four digits. The attribute, LU07, was added back to the coverage, and was calculated to equal LULC07. The JOINITEM command was then used to add the attribute IS07 to the .pat using IS07CAT as the join item. Once LU07 and IS07 had been added and correctly evaluated, ISLU07, and the redefined items associated with it could be deleted. This results in the coverage LULC07 having separate correctly defined fields for LU07 and IS07. Additional attributes, LABEL07 and TYPE07 were added to the .pat using the JOINITEM command, with LU07 serving as the join item. Two final attributes, ACRES and ISACRES07, were added and evaluated as follows: ACRES = AREA / 43560; ISACRES07 = IS07 / 100 * ACRES. Once all attribute fields were added and populated, final checks for node errors, label errors, and Invalid codes were run. Any errors were identified and corrected. Lastly the LULC07-ID field was calculated to equal LULC07# - 1, and the IDEDIT command run. The coverage containing only the 2007 wetlands polygons could then be created by reselecting the appropriate polygons from the LULC07 coverage All polygons with TYPE07 = 'WETLANDS' were selected and placed in the separate wetlands coverage. Errors checks as described above were again run on this layer, any needed corrections made, and the coverage, WET07, was loaded into the SDE geo-database for use in the web applications.