| Category |
Administrative/Ownership Data Base |
| Name |
.structures |
| Type |
Library Layer |
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| Abstract |
The Structures data layer is basically the outlines of apartment buildings. Structures are necessary to extend the ability to address match or locate individual dwelling units within the boundaries of larger properties. Traditional data base designs have included all structures outlines. Due to the additional expense in that approach, the City optioned to use the ability to observe structure outlines by viewing the Digital Orthophoto Image data layers. |
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| Maintenance |
Maintenance of City structure information continues using the "Parcel Maintenance System" developed in Arc Macro Language (AML) by ITSD for use in maintaining the Cadastral and Structure data layers. Configuration of Librarian tiles changed from Neighborhood to Section based structure in 1998 for simplification of maintenance procedures. Future plans include interfacing with SQL tables and expansion to additional classifications of structures. |
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| Source |
Large-Scale GIS Data Base Cadastral Base and Digital Orthophoto Images |
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| Agency/Contact |
Information Technology Services Department / mjohnson@ci.ann-arbor.mi.us |
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| Accuracy |
National Map Accuracy Standards for 1"=100', 1:1200, 1-2 foot positional accuracy |
| Projection |
NAD83 State Plane, Michigan South Zone 6401 |
| Units |
US Survey Feet |
| Spheroid |
GRS1980 |
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| Domain |
Quarter Sections within the Large-Scale GIS Data Base Development Project Area |
| Format |
Double Precision Polygon Coverage STRC_COV; Polygons with INFO attributes and related SQL table AAUIS.STRUCTURES |
| Tiles |
167 tiles approximating Quarter Section boundaries |
| Count |
2053 Polygons - 2071 Arcs |
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| Qualifications |
Existing City structure data files and paper diagrams were audited and converted for each quarter section within the Large-Scale GIS Data Base Development Area. The general procedure for creating the structure outlines included digitizing the building roof lines on screen in registration with a Digital Orthophoto background.
Accurate content and current nature of the Structure data is now much better due to maintenance application and the ability to show structures in relationship to property boundaries. |
| Qualifications |
Inconsistencies can be detected regarding the placement of structure outlines due to differences in radial displacement of taller structures in the original 1993 and updated 1997 imagery. These inconsistencies are being corrected as time allows. |
