Inventing a GIS
Execution
The basic components necessary to accomplish these goals were:
- "a geographic database (map library) that could model the electric system
- "an application to facilitate the design process and to update the map library and the
site inventory databases
- "computer hardware
- "software such as relational databases and middleware to connect the components
together.
The geographic database would reflect existing paper electric system maps of which four
distinct types were maintained:
- "inventory maps which depicted a large amount of detail for a relatively small area of
the system and included an inventory list for each site
- "operating maps which covered larger areas and included information on disconnects
and fuses
- "phasing maps which again covered large areas and included information on the
physical configuration of overhead conductors and the connected phase and size of
transformers and
- "tagging maps which showed the relationship between underground facilities. All
information except tagging would be incorporated into the map database.1
The design application would be required to:
- "add and remove design elements from a job
- "access corporate site inventory data
- "create work sketches and parts lists to support the construction process
- "maintain the necessary relationships, such as connectivity, in the electrical model
- "post design changes to map, inventory and related databases
The major requirements for computer hardware and related software would be cost
effectiveness and support for the first two components. Likewise the environment into
which the map library would be captured would be determined by the design application
chosen. Therefore specifications and an RFP for the design application were produced as
the first step in the process.
Proposals were evaluated and a pilot project was initiated in which a small portion of the
electrical system was converted and a design application created. This system, however,
did not fully meet some requirements and was completely unable to interact with legacy
systems. Further evaluation led to a second pilot project by Miner & Miner Consulting
Engineers of Greeley CO. Miner & Miner produced a database design, supporting
applications based on ESRI's Arcinfo AML (Arc Macro Language) and better
connectivity to IBM AS/400 legacy data. The second pilot project sufficiently
demonstrated the feasibility of the basic concepts of the system and was approved for
further development.
With a stable database design from the design application conversion specifications were
drafted and a conversion vendor, Cartotech Inc. of San Antonio TX.2, selected. The first
step in the conversion process was the creation of a base map comprised of PLS section
corners captured from the USGS 7½ minute quad map series. The next step in the
creation of the base map was to rubber sheet assessor's parcel maps into this framework.
Because mapping conventions varied over the District's four county service area and
because "local knowledge" helped in the interpretation of the source maps, district
personnel performed a clarification process or "scrubbing" prior to providing the source
material to the conversion vendor.
The District's electric inventory, operations and phasing maps were also scrubbed before
delivery to the conversion vendor. Data from the various system maps was to be captured
into a single map layer and delivered in native format i.e. ArcInfo coverages. A quality
assurance process was then performed on small areas as they were delivered. Corrections
were made where warranted and the vast majority of converted data has been used
without further adjustment.
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1. Tagging information, in the form of an image, is available to GIS users but that data, unlike data about
the rest of the electrical system, is not maintained as part of the design process.
2. Cartotech is now a division of Analytical Surveys, Inc.
