King County RECDNET

Probably the single most important data source in the analysis is the King County GIS parcel database, here referred to as RECDNET. RECDNET is the result of a massive project undertaken by the county's GIS division. Essentially, RECDNET is a vectorized version of the County Assessor's section maps (Figure 1), attributed with the Assessor's parcel data.

Scanned Assessor's Map Section

KC RECDNET

At the time of analysis, however, RECDNET was not in final release form, so most of the necessary parcel data were not available in this product. Luckily, the parcel identification numbers (PINs) were attached as attributes to the parcel polygons.

MetroScan

Although RECDNET did not contain attributes such as the number of units, property value, and building square footage, these data are available on MetroScan CDs (TransAmerica Corp.). We were able to select only SeaTac parcel records by selecting all records which matched the levy codes known to be in the City. MetroScan contains an exhaustive list of parcel attributes, most of which were unnecessary for the analysis. We only used the attributes we needed for this particular analytical task. Because these data are also referenced by PIN, relating the MetroScan data to the RECDNET polygon attribute table (PAT) was a trivial task. The typical MetroScan interface is a GUI in which a user queries the database and is returned matching records, in a condensed (Figure 2).

or more complete format (Figure 3).

We needed the output from MetroScan to be an input source for ARC/INFO, and fortunately MetroScan includes utilities for dBase and ASCII output. With a data dictionary provided from TransAmerica Corp., we were able to translate the cryptic internal names of MetroScan's database items into a more understandable form.

City of SeaTac GIS Data Layers

A few of the coverages in the city's GIS library were also used in the analysis, mainly to tag parcels with municipal-planning attributes (zoning, comprehensive plan designations),to limit the boundary of the study area, to flag areas of concern, such as wetlands, steep slopes, etc. These selected data sets are listed in Table 1.

City Limits polygon	Zoning polygon	Comprehensive Plan polygon
Urban Center polygon	Streams and Buffers line & polygon	Wetlands and Buffers polygons
Airport Use Area polygon	40º or Greater Slope polygon (from lattice)

Introduction Analysis