Home | GIS Online

   Ann Arbor Geographic Information System (AAGIS)

Ann Arbor GIS Metadata

Tiling Structure

Category Land Base Data
Name(s) atiles btiles ctiles dtiles etiles ftile
Description Tiling Structure
Type Coverages
Abstract Timely access and efficient maintenance of data depends on the storage of data layers in manageable units. These manageable units or tiles vary in size due to the density and/or type of data. Layers consist of rectangular tiles based on the State Plane coordinates, and are independent of administrative boundaries.
Maintenance The number and extent of the tiles was altered during the Large- Scale GIS Land Base Update Project due to the expansion of the original project area to meet the needs of the University of Michigan. Any further changes would be associated with project area expansion or interfacing with County data.
Source Large-Scale GIS Data Base Update Project (1997)
Information Technology Services Department - mjohnson@ci.ann-arbor.mi.us
Accuracy National Map Accuracy Standards for 1"=100', 1-2 foot positional accuracy
Projection NAD83 State Plane, Michigan South Zone 6401
Units US Survey Feet
Spheroid GRS1980
Domain Large-Scale GIS Data Base Update Project Area, 51.5 Square Miles
Format Double Precision Polygon Coverages; Polygons with INFO attributes
Count See Qualifications Table
Tile Names Tile Dimensions Tile Counts Associated Data Layers
atiles 1,000' by 1,500' 953 1/2' Image Catalog
btiles 2,000' by 3,000' 245 1' Image Catalog, Street Index
ctiles 4,000' by 6000' 72 2' Image Catalog, Planimetrics
dtiles 8,000' by 12,000' 23 4' Image Catalog
etiles 16,000' by 24,000' 6 8' Image Catalog
ftile 48,000' by 48,000' 1 16' Image Catalog

The boundaries of the tile coverages were created using the Arc/Info Command GENERATE.

xTILES.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 xTILES# 4 5 B -   * Polygon Internal ID
21 xTILES-ID 4 5 B -   - Polygon User Assignable ID
25 TILE-NAME 8 8 C - - - Tile Identification