Is Data Driving Your Fire Engine? Continued from page 36 There is one more use for assessor parcels: if you convert the parcel polygons to centroid points and associate the highly accurate and standardized assessor site addresses, you have an excellent, reasonably current E-911 geocoding point file! [See "The Call Comes In" in the Spring 2010 issue of ArcUser for more information on geocoding point files.] The district uses traditional cadastral data to define and map Fire Demand Zones (FDZs) and design response zones (or Fire Boxes). FDZs are defined by quarter section aliquots in PLSS. [An aliquot part is a standard subdivision of the area of a section based on an even division by distance along the edges, rather than equal area. Half section, quarter section, or quarter-quarter section are examples of these units.] In Washington State, the PLSS is administered by the Washington Department of Natural Resources. In your state, the land subdivision could be administered by the U.S. Bureau of Land Management or other agency. For additional information and to download PLSS data in the western or central United States, go to www.geocommunicator.gov/geocomm/lsis_home/home/index.shtm. In the district, recent, high-resolution imagery that was carefully rectified was used for validating the location, orientation, and footprint area for structures; the preferred method of access for large parcels; points of building ingress and egress; placement options for fire apparatus; and even fire hydrants. Public safety mappers are highly visual people who are continually finding new uses for aerial imagery. Kent City updates its high-resolution imagery every one or two years. In addition, a contractor provides biannual updates of registered vertical and oblique imagery. District staff is just starting to use the oblique imagery for prefire planning, building inspections, and tabletop scenarios. Fourth on My List—Administrative Units With streets and parcels mapped and studied, administrative boundaries can now be refined. Boundaries, including county lines, city limits, fire districts, and Urban Growth Areas (UGAs) [boundaries designed to contain urban sprawl] are defined and maintained on a cadastre. The county clerk/recorder or surveyor often maintains this data at the local level. Regional boundary information may be recorded by state agencies (e.g., transportation, public lands, environmental). Federal agencies, such as the U.S. Forest Service, Bureau of Land Management, and Federal Emergency Management Agency (FEMA), can also provide boundary information. At the Kent Fire Department, municipal and district boundaries are maintained by King County and Kent City. King County also maintains county, special district, and other boundaries countywide. Examples of special district boundaries for natural hazards and areas of environmental sensitivity are defined and maintained by the Washington Department of Ecology, Washington State Emergency Management District, FEMA, and other agencies. The district includes regions of rapid urban and suburban growth. State-defined UGAs are essential, as they predict where and when additional services will be needed. During the 2009 reaccreditation, UGA-based growth projections provided key planning information. In a broad sense, all strategic/master plans and capital facility plans are guided by growth boundaries. Fifth and Sixth—Elevation and Hydrography As an old firefighter and geologist, I have combined these two framework pieces and placed them toward the bottom of the list. However, in areas with certain natural hazards, these datasets should probably be listed first. Digital terrain data, including 10-meter digital elevation data, is available nationally from the U.S. Geological Survey (USGS) Seamless data site (seamless.usgs.gov). Digital hydrography is available nationally from the National Hydrography Dataset at nhd.usgs. gov/data.html. Riverine inundation data may be previewed at FEMA’s Map Service Center at msc.fema.gov. Data may be ordered from this site or it may be available without charge through your county or state emergency manager. Other terrain and water-based hazard information could be available through county or state emergency or engineering agencies. In the district, 10-meter USGS terrain data provides a regional base. The Puget Sound Lidar Consortium provides terrain data as grids with 6-foot pixel resolution throughout the southern county. By combining high-resolution terrain with imagery, hydrography, geolwww.esri.com Assessor parcels, high-resolution imagery, transportation systems, and the Public Land Survey System (PLSS) combine to map parcel and building-level occupancies in the City of Kent. Third Choice—Orthoimagery With street alignment and parcel boundaries on a map, the next step is checking those layers against imagery. Imagery is the third item on my list because it can be used for visually validating the streets and parcels in coordinate space. Current, high-resolution imagery is an invaluable tool for viewing and understanding many aspects of a street dataset including street alignment, lane count, intersection geometries, road width, and new construction. Aerial imagery shows the relationship between street edges, street centerlines, and parcel edges. It also shows the placement and orientation of structures on parcels. This is especially helpful when mapping and addressing apartments or condominiums that have many residential units on a single tax parcel. At the wildland-urban interface, imagery provides a quick way to visualize fuels and measure the distances separating hazardous fuels from structures. In these areas, it is best to obtain two recent imagery sets—one with leaves on trees and one with leaves off trees. 38 ArcUser Summer 2010