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Ann Arbor GIS Metadata


Category Administrative/Ownership Data Base
Name .structures
Type Library Layer
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.
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.
Source Large-Scale GIS Data Base Cadastral Base and Digital Orthophoto Images
Agency/Contact Information Technology Services Department / mjohnson@ci.ann-arbor.mi.us
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
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
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.

STRC_COV.PAT - Polygon Attribute Table Definition and Content

Column Field Name Width Output Type N Dec Alt Name Indexed? Field Content
1 AREA 8 18 F 5   - Polygon Area (square feet)
9 PERIMETER 8 18 F 5   - Polygon Perimeter (feet)
17 STRC_COV# 4 5 B -   * Polygon Internal ID
21 STRC_COV-ID 4 5 B -   - Polygon User Assignable ID
29 STRUCTURE_ID 3 3 C -   - Structure Identification Number
32 LPIN 10 10 C -   - Land Parcel Identification Number
42 KFEAT 4 6 B -   - Symbolization Code