GIS of County Address Map Series for City of Carson, California

Address maps, originally produced by the Los Angeles County Public Works Department, are used daily by city of Carson planners and building officials. This series of 57 maps provides information about parcel lines, permits, easements, zoning, and a variety of redevelopment area and overlay boundaries all in a large-scale format that facilitates discussion with applicants across city hall's front counter.

In 1999, the county relegated the responsibility for updating these maps to the city. The county converted the hand drawn maps to CADD files and provided these to the city. Carson Geographic Services began updating map notation and some line work in AutoCAD; however, weekly parcel line changes, redevelopment area amendments, and other ongoing boundary revisions were only made to GIS data layers. The need to convert the address map series entirely to GIS soon became clear.

Several issues had to be addressed from the outset. The first was transformation of the CADD files to the city's coordinate system. CADD files were produced in unprojected planar coordinates, and the city uses California State Plane Zone V, 1983 Datum. The second issue was to limit the GIS data layers to each map's area of detail. This was accomplished through the creation of a new geodatabase polygon feature, an address map index. Converting CADD annotation to GIS layers became feasible with the advent of the geodatabase feature type.

Address maps contain line features that are not available through the GIS library. These chiefly include those associated with annotation (pointers and text boxes) and lot lines. A special class of line work that the city wanted as a separate data layer was easements. All easements in the city for sewer, water, or other utility lines; storm drains and catch basins; and private fire lanes and driveways are included. The final data layer contained more than 900 features.

All other data layers included in the address maps (parcels, zoning, redevelopment areas, overlays, and city outline) derive from existing GIS data layers. An agreed symbolization scheme for each was saved as a layer file. The introduction of color, showing zoning designations, was one of the most noticeable and best received of the changes in the new address maps.