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Some of the terms listed below are specific to Place-n-Time.  Some are specific to SDTS.  Some are used by both.  When definitions are given for SDTS terms, the definition applies to the term only as used by Place-n-Time.  (For instance, definition 2 given here for CATD says that CATD is the name of the catalog/directory module; this is true in the Place-n-Time world, which currently uses only the Topological Vector Profile, but may not be true for other profiles which are not used by Place-n-Time.)

Brief definitions given here are sometimes followed in smaller print by quotations from the appropriate SDTS document.  These definitions are here for convenience, but should not be considered a substitute for the original documents.  For the best definition, consult the latest versions of those documents.



 

ATID

Mnemonic for the Attribute ID, which is a module field containing an integer indicating the Record ID within an Attribute Primary module.

In the SDTS Logical Specifications, the description of the Attribute ID is defined for each transfer module record type.  For many modules it is described simply as the "Foreign identifier for Attribute Primary module Record."
 

CATD

1.  Mnemonic for Catalog/Directory, which is a field in the catalog/directory module.

SDTS, Part 1, Section 5.2.2.1 says, "This module contains information on where to locate all modules within the transfer."

2.  Name of the catalog/directory module

SDTS, Part 4, Section 4.1 says, "Non-object modules shall be named the same as the primary module field mnemonic."

3.  Field in the What's This description boxes used for the pathname of the catalog/directory module's file.

See What's This: Show IDs.
 

DLG-3

Digital Line Graph, level 3. The United States Geological Survey (USGS) creates digital map data sets in vector form. They call these sets DLG-3 data. Most (possibly all?) SDTS transfers that are supported by Place-n-Time are based on DLG-3 data sets.

The USGS's Data Users Guide 1: Digital Line Graphs from 1:24,000-Scale Maps says:

The term Digital Line Graph (DLG) is used by the USGS to describe a digital map data set in vector form. Originally, three levels of DLG data (DLG-1, DLG-2, and DLG-3) were envisioned; these levels were differentiated by their positional accuracy, level of attribute coding, and relational spatial information. It was found, however, that the widest user-community would be served by producing DLG-3 data, which have the full range of attribute codes and are fully topologically structured.

ENID

Mnemonic for Endnode ID, which is a field in the line module containing an integer indicating the identity of the record within the point-node module for the point-node at the end of the line.

In the SDTS Logical Specifications, the End Node ID is described as "Foreign identifier of end node Point-Node module record."
 

GNIS

GNIS is the Geographic Names Information System, which was created by the United States Geological Survey in cooperation with the U. S. Board on Geographic Names to hold information on geographic features (both physical and cultural) in the United States and its territories.
 

Module

A group of SDTS records commonly (but not necessarily) contained in a single file.

Or, from the SDTS Logical Specifications:

1.5.20  Module - A logical collection of module records.
1.5.21  Module field - A defined set of one or more module subfields in a Spatial Data Transfer.
1.5.22  Module record - A defined set of one or more module fields in a Spatial Data Transfer.
1.5.23  Module specification - The meaning, identification, order requirements, and data structure requirements for data belonging to the module.
1.5.24  Module subfield - A logical construct defining a single data element in a Spatial Data Transfer.

 

RCID

Mnemonic for Record ID, which is a module subfield containing an integer indicating the identity of the record within a given module.

In the SDTS Logical Specifications, the description of the Record ID is defined for each transfer module record type.  For instance it is described as the "Line object record identifier" for the line module specification, and as the "Polygon object record identifier" for the polygon module specification.  But for many modules it is described simply as "a number for the module record, unique within the module," which is a useful overall description.
 

SNID

Mnemonic for Startnode ID, which is a field in the line module containing an integer indicating the identity of the record within the point-node module for the point-node at the start of the line.

In the SDTS Logical Specifications, the Start Node ID is described as "Foreign identifier of start node Point-Node module record."
 
 

Theme

A subset of the surface data containing objects of a similar nature.  For instance, Place-n-Time currently supports the following themes:
Boundaries
Hydrography
Roads & Trails
Railroads
Miscellaneous Transportation
Or, from the SDTS Logical Specifications:
1.5.36  Theme - A generalization of entity classes (e.g., culture, hydrography, transportation).

Transfer

An SDTS transfer is a set of map data (usually corresponding to one theme of one map) which is in the format defined by the Spatial Data Transfer Standard. The term "transfer" refers to the fact that this format was created to allow map data to be transfered from one computer system to another. Although SDTS transfers were intended to be converted, after transferring, to a format readable by the applications on the destination computer system, some applications (including Place-n-Time) can read SDTS transfers without conversion to another format.

Or, from the SDTS Frequently Asked Questions:

SDTS transfers are the data sets used to exchange spatial data between different computer systems. SDTS transfers consist of a series of modules (the SDTS's logical grouping of related data) encoded into files using ISO 8211 standard, "Specification for a Data Descriptive File for Information Interchange" (ANSI 1986).

Vertical Relation

An attribute describing the relationship between two features where one passes over or passes under another, as in the case of a bridge.

Or, from the DLG-3 Master Data Dictionary / Definition file:

This attribute describes the vertical relationship of a feature to another feature.  Examples are features which overpass or underpass other features.


Copyright © 2008 by Dapper Mapper


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