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2007-12-21


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ESRI

ESRI Shapefile

Simple Definition: A file format created by ESRI that is used to store simple geospatial features.

Additional Explanation or Clarification: A Shapefile is represented at a minumum by a file with a DBF extension and a file with a SHP extension. An index file with a SHX extension may also be included. Shapefiles only store a single geometry type. They can optionally store z ordinate and "m" ordinate values in geometry coordinates.

Example: The United States Census Bureau TIGER Data can be obtained for most counties in the United States as ESRI Shapefiles. Visit this page to for downloads of these Shapefiles.

Associated Terms:

Also Known As:

  • Shapefile

References: Wikipedia Shapefile Entry

Links: ESRI Shapefile Specification

GDAL Shapefile Information

Feature

Feature Geometry

Feature Attribute

Feature Schema

FGDC Metadata

Geospatial

Geospatial Data Set

Simple Definition: A set or group of geospatial data with a common theme or association.

Additional Explanation or Clarification: Features belonging to a geospatial data set typically share a common feature schema or set of feature attributes. The term does not typically refer to a single feature. Geospatial datasets are often represented in a GIS by a thematic layer. Geospatial datasets are typically the main elements in a GIS Data Model.

Example: An ESRI Shapefile with a set of line features representing city streets could be called a Geospatial data set.

Associated Terms:

  • Gespatial Dataset Definition

Also Known As:

  • Data Set

References:

Links:

Geospatial Data Set Lifecycle

GIS

GIS Data Model

Geospatial Metadata

Simple Definition: Information about geospatial data that may not be contained in, or readily apparent from, the geospatial data itself.

Additional Explanation or Clarification: Metadata is often defined as "data about data". As an example, you might have metadata for a document might include the following information:

  • Identify the purpose of the document.
  • The date the document was written.
  • The date the document was last revised.
  • The author.

Geospatial Metadata is information about a geospatial dataset that may not be contained in, or may not be readily apparent from, the Geospatial dataset itself. For example, you could view the coordinates of feature geometry in a vector data set, but may not be able to determine the spatial reference system from the coordinate values. You could view the name of a feature attribute, but that may not indicate what aspect of the real world that attribute represents. This is the type of inormation that can be encapsulated in geospatial metadata.

Example: Information about the [Example: An feature schema or feature attributes common to a group of features. This might include the meaning of the attribute name, the data type of the attribute, and rules for the creation, deletion, and modification of the attribute values.

Associated Terms:

Also Known As:

  • Metadata
  • GIS Metadata

References:

Links:

Geospatial Metadata Instance

Simple Definition: A single and specific metadata document, typically created in conformance with a metadata standard.

Additional Explanation or Clarification: There is typically a metadata instance for each geospatial dataset in a GIS. The term "metadata instance" can be used to distinguish a specific metadata document from all metadata documents that conform to a particular metadata standard, or from the metadata standard itseld. (In a similar way, an isntance in object-oriented programming is different than the class or interface to which the instance conforms.)

You could think of a metadata standard as a cookie cutter, and a metadata as an individual cookie made from that cookie cutter.

Example: If you had a GIS that managed road data and car accident data in ESRI Shapefiles, you would have a metadata instance for each shapefile. One metadata instance might be named roads_metadata.txt while the other was named car_accidents_metadata.txt.

Associated Terms:

Also Known As:

  • Metdata Document

References:

Geospatial Metadata Standard

Simple Definition: A metadata standard or specification is a document that contains rules or guidelines for the content of metadata.

Additional Explanation or Clarification: Metadata standards can be created specifically for use within a particular organization, or for much broader adoption. They allow for the creation of tools, often with a graphical interface, that can be used to create and modify metadata that meets the standard. They may also allow the metadata to be validated against the standard. This is another way of saying that instances of the metadata can be checked for conformance with the standard.

Example: The FGDC Metadata Standard is an example of a metadata standard.

Associated Terms:

Also Known As:

  • Metdata Specification

References: A directory of metadata standards at the University of Brussels

Open Source Geospatial Foundation

your are in right now :)

Raster Data

Shapefile

See ESRI Shapefile

Simple Feature

Thematic Layer

Vector Data