Most municipal geography information systems are started with the creation and management of digital
parcel geography for Assessors and Assessing Departments. Once detailed assessing parcel maps have
been digitized, the resulting data becomes available for many other uses within local government.
The areas where GIS utilization is most common are: real property assessment and taxation; utilities
and water management; open space and land management; planning and development control; transportation
management and planning; emergency management and crisis handling, etc.
Parcel Data Development:
The parcel data development process, also referred to as parcel geometry development or parcel digitization,
involves the conversion of paper maps and/or AutoCAD geography files into a property level geography
information system (GIS). Typically this entails the tracing of individual property lines and the
identification of each property with a unique identifier that can be connected to an existing information
database (assessing records).
Geocoding is very often a misunderstood term. In a general sense, it refers to the association of a series of
geographic references to a list or tabular dataset. Typically for an address list, this means an
association of x-y or lat-long coordinates. In a GIS map, these coordinates are depicted as a simple
point on the GIS base map. One point represents each record from the listing or dataset.
The accuracy of these x-y references sometimes creates confusion when utilizing geocoded data within
a GIS. Listings can be geocoded at various levels and it depend on the base map that is used whether or
not a geocoded list can be appropriated used on that base map. For example, some lists may be geocoded
to zip code boundaries only. In these cases, points can only be portrayed on a base map depicting zip code
geography or larger aggregate geography. Listing data can be georeferenced to any geographic area, however
most typically geocoding is performed by zip code boundaries, address locations, parcel geography or
Raster Data & Ortho Images:
Raster data is represented by square and rectangular pixels. It is a different form of GIS data that is
not often used in consumer application except as a visual aid and reference. However it is used in the
development of standard GIS data such as parcel geography systems.
In the development of parcel geography, an aerial orthography photo image (raster data) is used to
register scanned assessing maps. (These scans are also raster based data images.) The parcel lines on the
assessing maps are traced converting raster data into what is called vector data. Vector data is
information represented by point, lines and polygons.
Internet & Web Mapping:
Internet Mapping is quickly becoming the desired method of viewing an analyzing GIS data. Unfortunately,
the delivery of vector graphics through the web is only in its infancy. Typically web based Internet
applications require a map server running from the host server location. The map server creates temporary
images on the server and delivers them through web to be rendered on the client’s Internet browser.