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| Case Study |
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Patni's GIS solution for Tax-Parcel Mapping increases tax revenues for City of Chicago |
Patni's solution has resulted in streamlined processes, huge savings on expenditure and high tax earning from correct valuations.
The Client
The City of Chicago, Illinois, US
The Challenge
In the City of Chicago, the Assessor's Office estimates the value of parcels of real estate, bringing in several thousand dollars annually in taxes. These valuations were, however often challenged and not defendable. The major problem was that determining property values was cumbersome and prone to error, since all the tax maps and their several copies were manually drafted / updated, filed and maintained. Moreover, to conduct valuations, maps had to be compared manually with lists of statistics.
The City, therefore, needed to convert parcels, maps and scales as part of digitization and creation of Arc/Info coverages. The input data included scanned images of map sheets and base maps in .dgn format. The scope of the project included conversion of 720,000 parcels from 2072 maps divided in 259 sections with each section containing 8 map sheets. The entire project, driven by stringent deadlines, was to be executed within a short span of eight months.
The Solution
Patni developed the datasets in two different GIS Platforms, Viz. ESRI's Arcinfo and Intergraph's MGE (Modular GIS Environment). The major challenge was that both platforms support data in different formats. The data initially developed in Microstation environment, then converted to MGE and built into Archinfo coverages.
Highlights of data requirements
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Digitize data from scanned images to contain features such as: roads, railroads, highways; ROWs and polygon features like parcels condominiums, vertical parcels, blocks, sections, district boundaries, town boundaries, lakes, water bodies, marshy lands; Condominium parcels for every floor as individuals .dgn files. |
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Block face with a positional accuracy of 0.2" of the corresponding features in the DPD base file |
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Attribution within a permissible limit of 2% of total attributed elements. |
GIS Process
Patni made extensive use of tools, developed inhouse, to maintain the quality of the data during digitization and to meet the stringent delivery schedule. The data developed in Microstation was migrated into Intergraph MGE. Routines were developed using MDL (Microstation Development Language) for this conversion.
The data was converted into Arcinfo GIS format using AML applications, to automate the conversion process. Condominium parcels were digitized so as to enable 3D coverage configuration in the future.
The Technology
The Benefits
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Digitized and always current tax maps available across departments of the City |
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Streamlined processing and dissemination of uniform and accurate information |
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Huge savings on storage and considerable reduction in human resources required. |
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New spatial data warehouse enables recovery of huge revenues, well in excess of the cost of the system |
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Higher earning in tax revenues from being able to defend valuations in court (property records are instantly linked to GIS datasets and are accessible to provide spatial reference). |
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