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3. Spatial Data Organization



Spatial Data Organization describes the mechanism used to represent spatial information in the data set. This section contains definitions and examples for the following metadata elements.

Indirect Spatial Reference
Direct Spatial Reference Method
Point and Vector Object Information
Raster Object Information


Indirect Spatial Reference


Definition
: The name of types of geographic features, addressing schemes, or other means through which locations are referenced in the data resource.

"Indirect spatial reference is any way to describe a location without using coordinates. Indirect spatial reference methods usually use a geographic feature, such as a county, state, township or section of the Public Land Survey System, or a road, to uniquely identify a place. The reference may use the name of the feature (for example "Westmoreland County") or a code that identifies the feature (such as a county FIPS code). Other examples of indirect spatial references include street addresses, linear reference systems, and River Reach codes.

Indirect spatial references are [important] because they are a very common means by which observations of other attribute information are tied to a place. The location of many socioeconomic, environmental, and other data often are referenced by identifying a unit of political geography (e.g. block, block group, or tract), street address, linear referencing system (e.g. milepost), and so on. While these indirect spatial references alone may not be sufficient for geographic analyses, they can serve as a means to link the attribute data to coordinate descriptions of the places to which the attribute data apply."
1

Format
: Free text.

Example
:


Direct Spatial Reference Method


Definition
: The system of objects used to represent space in the data resource.

Format
: Select from list: Point, Vector, Raster.

Example
:
Direct Spatial Reference Method
: Raster



Point and Vector Object Information


Point and Vector Object Information contains the types and numbers of vector or non-gridded point spatial objects in the data resource. This metadata element encompasses the following sub-elements.

SDTS Point and Vector Object Type


Definition
: The name of point and vector spatial objects used to locate zero-, one-, and two-dimensional spatial locations in the data resource. Terminology provided for the point and vector objects is drawn from the Spatial Data Transfer Standard (SDTS).
2

Format
: Select from the following list:

SDTS list:
Point
Entity point
Label point
Area point
Node, planar graph
Node, network
String
Link
Complete chain
Area chain
Network chain, planar graph
Network chain, nonplanar graph
Circular arc, three point center
Elliptical arc
Uniform B-spline
Piecewise Bezier
Ring with mixed composition
Ring composed of strings
Ring composed of chains
Ring composed of arcs
G-polygon
GT-polygon composed of rings
GT-polygon composed of chains
Universe polygon composed of rings
Universe polygon composed of chains
Void polygon composed of rings
Void polygon composed of chains


Point and Vector Object Count


Definition
: The total number of the point or vector object type occurring in the data resource.

Format
: Point and Vector Object Count > 0

VPF Topology Level


Definition
: the completeness of the topology carried by the data set. The levels of completeness are defined in Vector Product Format (VPF).
3

Format
: Integer; 0 <= VPF Topology Level <= 3

VPF Point and Vector Object Type


Definition
: The name of point and vector spatial objects used to locate zero-, one-, and two-dimensional spatial locations in the data set. Terminology provided for the VPF point and vector objects is drawn from Vector Product Format (VPF).

Format
: Select from list: Node, Edge, Face, Text.

Point and Vector Object Count


Definition
: The total number of the point or vector object type occurring in the data set.

Format
: Integer; Point and Vector Object Count > 0.


Raster Object Information


Raster Object Information provides the types and numbers of raster spatial objects in the data set. This metadata element encompasses the following sub-elements.

Raster Object Type


Definition
: Raster spatial objects used to locate zero-, two-, or three-dimensional locations in the data set.

Format
: Select from list: Point, Pixel, Grid Cell, Voxel.
With the exception of "Voxel", the terminology provided for Raster Object Type is drawn from the Spatial Data Transfer Standard (SDTS).
2

Row Count


Definition
: The maximum number of raster objects along the ordinate (y) axis. For use with rectangular raster objects.

Format
: Integer; Row Count > 0

Column Count


Definition
: The maximum number of raster objects along the abscissa (x) axis. For use with rectangular raster object.

Format
: Integer; Column Count > 0

Vertical Count


Definition
: The maximum number of raster objects along the vertical (z) axis. For use with rectangular volumetric raster objects (voxels).

Format
: Integer; Depth Count > 0


References


1
Federal Geographic Data Committee (FGDC). 1995. Content Standards for Digital Geospatial Metadata. Workbook (March 24). Washington, D.C.: FGDC. pp.3-1.

2
U.S. Department of Commerce. 1992. "Spatial Data Concepts". Part 1, Chapter 2, in Spatial Data Transfer Standard (SDTS) (Federal Information Processing Standard 173). Washington, D.C: U.S. Department of Commerce, National Institute of Standards and Technology.

3
U.S. Department of Defense. 1992. Vector Product Format (MIL-SDT-600006). Philadelphia: U.S. Department of Defense, Defense Printing Service Detachment Office.



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Revised: March 1998.
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