DRAFT
Transportation Spatial Data Dictionary
Prepared for
Federal Geographic Data Committee
Ground Transportation Subcommittee
by
Matthew Rabkin/Sarah Maccalous
U.S. Department of Transportation
Research and Special Programs Administration
The Volpe Center
March 25, 1997
TABLE OF CONTENTS
Introduction
Review Process
Spatial Presentation Definitions
Spatial Features
ACCIDENT SITE
AIRPORT
BRIDGE
CROSSING
HARBOR
INTERMODAL TRANSFER FACILITY
JUNCTION
LINEAR REFERENCE POINT
LOCK
PIPELINE
PORT
RAILWAY
ROADWAY/HIGHWAY
ROUTE
RUNWAY
TERMINAL
TRAIL/PATH
TRANSPORTATION FACILITY
TRANSPORTATION SYSTEM
TRANSIT GUIDEWAY
Introduction
The Federal Geographic Data Committee's (FGDC) Ground Transportation Subcommittee is developing a Transportation Spatial Data Dictionary as an initial step toward the standardization of both definitions and spatial object presentations for transportation features. This draft document will be amended based on comments received from the transportation GIS community and will result in a section to be incorporated into the document, Spatial Data Transfer Standard: Part II - Spatial Features.
We are distributing the draft dictionary at this time for informal review by the transportation community. Our objective is to obtain feedback concerning:
This document represents work currently in progress. We have not tried to develop a complete list of all transportation features at this time. Instead, we have included what we believe is a representative set of features spanning all transportation modes and spatial object presentations. If the feedback we receive suggests that the document is potentially useful, and that the proposed classification scheme is appropriate, we will include additional transportation features as recommended by the transportation community.
Format for the Dictionary
Each transportation feature in this dictionary is identified by a standard term, a definition for that term, and a spatial presentation which identifies one or more spatial objects that may be used to represent the feature in a geo-spatial database. There may also be one or more related terms which identify special cases or alternative names for the transportation feature.
At the end of this data dictionary, we have created an alphabetical index which cross-references all of the standard and related terms against their associated standard term. This allows "you" to easily find those features that might not be listed as a standard feature in the Table of Contents.
Assumptions and Unresolved Issues
As you read through this draft dictionary, please consider the following organizational questions in addition to any specific comments you have on current definitions or additional features that you would like to see included.
The dictionary is structured along modal lines. The primary transportation modes are air, water, rail, roads, pedestrian, pipeline, and transit. Each mode has an associated network composed of links or travel ways uniquely suitable for that mode (e.g., trains can't run on roads), junctions where two or more links intersect, and access points where people and/or goods can get on or off the mode. There are also transportation features where different modes intersect, either to exchange people and goods (i.e., intermodal facilities) or where networks simply cross (i.e., crossings). Finally, there are features which are common to multiple modes (e.g., bridges and tunnels).
Question: Is this modal-based structure a useful way to organize the spatial data dictionary? If not, what other structure is more useful?
The transit mode is currently treated as a generic mode for a number of different fixed guideway passenger systems (e.g., heavy rail, light rail, monorail, etc.). If we were to strictly adhere to the principle that a mode is defined by its unique travel way (e.g., monorail trains can't operate over light rail tracks), then each of these systems should be identified as a separate mode.
Question: Should fixed guideway transit be treated as a single mode, or broken out into the various guideway systems?
Use of the related terms category in this dictionary has been somewhat informal. Related terms currently may include: 1) the included term as defined in SDTS: Part 2 to mean another term with essentially the same meaning as the standard term (e.g., "street" as an included term of "road"); 2) terms that represent a specific type of the standard term (e.g., "TOFC" is a special type of "Intermodal Transfer Facility"); or 3) terms that may actually represent a different transportation feature (e.g., should "heliport" be treated as a type of "airport" or put in its own category?). The current use of related terms raises several questions:
Question: Should the dictionary use included terms at all? If yes, what should be the criteria for listing terms as included terms?
Question: Should the dictionary include attributes, or at least a type attribute for standard terms? If yes, should this category be in addition to or in place of included terms?
Question: Which of the current related terms should be moved out to their own standard term?
One of the terms currently included in the dictionary is a generic "catch all" for transportation facilities (e.g., buildings and defined areas) that are components or appurtenances to a transportation network. The "transportation facility" category is further divided along modal lines. The potential number of new standard terms contained within these categories would increase the size of the transportation spatial data dictionary enormously.
Question: Which of the terms included under transportation facilities should be moved out to their own standard term?
Question: As an alternative to a single "transportation facility" term, should the mode-specific facilities currently included as "related terms" be moved out to their own standard term?
While there is an implicit data model underlying the features and definitions currently included in the dictionary (i.e., a mode-specific network model which focuses on access points and intermodal connections), we have not attempted to explicitly describe it.
Question: Should the underlying model be explicitly included as part of the dictionary?
We have allowed the definitions for roadway and route to be somewhat ambiguous with respect to spatial presentation (both a roadway and a route may be depicted as a traversal; a roadway may also be depicted as a line). This ambiguity reflects the current lack of consensus within the transportation GIS community regarding how a roadway (or any other transportation network linear feature) should be segmented. For example, a roadway may be represented by a new line segment at each intersection, whenever a certain attribute changes (e.g., road name or number of lanes), whenever a political boundary is crossed, or any combination thereof. There is no correct or universally agreed upon way of specifying an elemental unit of roadway.
The current definitions provide sufficient flexibility to allow database developers to define roadways any way they want. However, this flexibility may also make it more difficult to share linear spatial data, or to transfer collected attribute data from one spatial representation to another spatial database.
Question: Should this dictionary be more specific (and more restrictive) in its definition of roadways, waterways, railways, etc. to provide explicit rules for deciding how these features should be segmented?
Paper copies of this draft will be distributed at several national GIS and transportation conferences during 1997. An electronic version will also be posted on the Bureau of Transportation Statistics (BTS) World Wide Website:(http://www.bts.gov/gis/reference/tsdd.htm).
The comment period for this draft document will continue through the end of June 1997. Reviewers may submit written comments to:
Office of Geographic Information Services
Bureau of Transportation Statistics
400 Seventh Street, SW
Washington, DC 20590
Fax: 202-366-3640
E-Mail: tsdd@bts.gov
Reviewers may also submit comments directly from the document located on the BTS Website.
After the comment period has closed, the Transportation Spatial Data Dictionary will be revised and submitted to the FGDC Standard Working Group for adoption as an FGDC standard. The standards process includes at least one more round of "official" public review and comment. Hopefully, all major deficiencies and problems will already have been identified and addressed. If no additional serious issues are raised, the transportation feature definitions included in the dictionary will become part of the Spatial Data Transfer Standard.
Spatial Presentation Definitions
The following definitions are used throughout this document to indicate the appropriate spatial objects used to represent each transportation feature. Unless otherwise noted, the definitions are taken directly from the Spatial Data Transfer Standard (SDTS), Part 1: Logical Specifications.
Point |
A zero-dimensional object that specifies geometric location. One coordinate pair or triplet specifies the location. Point features, as used in this document, are typically represented as an Entity Point, defined in SDTS as "a point used for identifying the location of point features (or area features collapsed to a point)." |
Line |
A one-dimensional object containing two or more points. SDTS defines five specific implementations of a line: 1) line segment, 2) string, 3) arc, 4) link, and 5) chain. A line, as used in this document, may be any of these implementations. |
Area |
A bounded, continuous, two-dimensional object. Area features, as used in this document, may be represented as a G-Polygon or GT-Polygon. |
Image |
A two-dimensional array of regularly spaced picture elements (pixels) constituting a picture. As used in this document, an image is used strictly for visual presentation and contains no attribute data. |
Graph |
A set of topologically interrelated zero-dimensional (node) and one-dimensional (link or chain) objects that conform to the following defined constraint rules: 1) each link or chain is bounded by an ordered pair of nodes, not necessarily distinct; 2) a node may bound one or more links or chains; 3) links or chains may only intersect at nodes. As used in this document, a graph may be implemented as either a planar graph or network. |
Spatial Features
ACCIDENT SITE
Definition : A location where an event occurred by chance or can be attributed to carelessness, unawareness, ignorance or a combination of causes which results in physical damage and/or injury. An accident can involve a single transportation vehicle, single mode or multiple modes.
Spatial Presentation: Point, Area
Related Terms:
Capsizing
When a vessel or ship turns upside down.
Collision/Crash
An impact between a transportation vehicle and some object including another vehicle, pedestrian, animal, or fixed object.
Derailment
When one or more units of rolling stock leaves the rails during train operations for causes other than a collision, explosion, or fire.
Grounding
When a vessel strikes rocks, reefs, shoals, or beaches such that the vessel becomes temporarily or permanently stranded.
Jackknife
When a truck tractor and the trailing unit it is pulling rotate with respect to each other and the roadway.
Rollover
When a motor vehicle overturns 90 or more degrees.
Rupture
A break or breach in a pipeline.
Sinking
When a vessel loses enough buoyancy to permanently settle below the surface of the water.
ACCIDENT SITE
Related Terms Continued:
Spill
The unintentional release of a solid, liquid, or gas from a transportation mode.
Definition: Any area located on land, water, or structures, which is used for the landing and take-off of powered or non-powered aircraft. An airport may include facilities for the shelter or servicing of aircraft, or for receiving and discharging passengers or cargo.
Spatial Presentation: Point, Area, Image
Related Terms:
Gliderport
An airport whose primary purpose is the take-off, landing, support and maintenance of gilders.
Helipad
An area located on a building or in close proximity to a building that is designed for helicopters to take-off and land.
Heliport
An area used for the take-off, landing, maintenance and fueling of helicopters.
Seaplane Base
A facility located on or adjacent to a body of water that is used for the docking, maintenance, and fueling of seaplanes.
BRIDGE
Definition: A structure spanning a depression, a body of water, or a transportation right-of-way which provides a travel way for transportation vehicles, pedestrians, or a pipeline.
Spatial Presentation: Point, Line
Related Terms:
Causeway
A raised way over wet ground or water.
Culvert
A drainage structure beneath an embankment. Culverts, as distinguished from bridges, are usually covered with embankment and are composed of structural material around the entire perimeter.
Elevated Highway
A raised roadway constructed over wet ground, water, another transportation right-of-way, or other physical feature.
Footbridge
A structure designed to carry pedestrian traffic only.
Overpass/Underpass
A crossing of two transportation rights-of-way at different levels where clearance to traffic on the lower level is obtained by elevating the higher level or where clearance to the upper level is obtained by depressing the lower level.
Span
The passageway between two supports.
CROSSING
Definition: A location where two or more segments of different transportation model networks intersects another. See: Junction, Bridge
Spatial Presentation: Point, Line
Related Terms:
Ford
A shallow section of a river that allows motor vehicles or pedestrians to cross without the aid of a bridge or ferry.
HARBOR
Definition: An area of water where ships or other watercraft can anchor or dock safely. See: Port
Spatial Presentation: Point, Area
INTERMODAL TRANSFER FACILITY
Definition: An area or enclosed structure that provides a connection for passengers and/or goods from one transportation mode to another. See: Airport and Port
Spatial Presentation: Point, Area
Related Terms:
COFC (Container-On-Flatcar)
A facility that is designed specifically for the transfer of freight containers to or from a rail flat car.
TOFC (Trailer-On-Flatcar)
A facility that is designed specifically for the transfer of trailers to or from a rail flat car.
JUNCTION
Definition: A location where two or more segments of the same transportation modal network intersect. See: Crossing
Spatial Presentation: Point, Area, Image
Related Terms:
Confluence
The point where two or more links in a waterway network come together.
Intersection
The point where two or more links in a single transportation mode come together at grade and where a transportation vehicle can turn from one link onto another.
Interchange
An area and structures that are designed to provide traffic access between roadways of differing levels or grades.
LINEAR REFERENCE POINT
Definition:A monumented or measured point along a designated route of a modal transportation network from which distance measurements are made to locate other features situated along the route.
Spatial Presentation: Point
Related Terms:
Address
A reference number developed to locate a building or property along a named roadway.
Kilometer Point/Milepoint
A measured distance along a designated route or path from an established origin point.
Mile Marker/Milepost
A signpost or other monument located along a transportation way indicating a historic distance, in miles, measured along the designated route from an established origin point.
LOCK
Definition: A channel having watertight gates at both ends built for the purpose of raising or lowering the water level to allow vessels to pass the obstruction.
Spatial Presentation: Point, Line
PIPELINE
Definition: A continuous pipe conduit, complete with equipment such as valves, compressor stations, communications systems, and meters for transporting slurry, liquid and gasses from one point to another.
Spatial Presentation: Line, Traversal
PORT
Definition:A landing place for waterborne transportation with terminal and transfer facilities for loading and discharging cargo or passengers. See: Harbor.
Spatial Presentation: Point, Area
RAILWAY
Definition: A maintained way consisting of two parallel rails for the passage of trains.
Spatial Presentation: Line, Traversal
ROADWAY/HIGHWAY
Definition: A cleared and maintained way for the passage of motor vehicles.
Spatial Presentation: Line, Traversal
Related Terms:
Alley
A narrow roadway, generally between buildings.
Avenue
A broad, multi-lane roadway usually in an urban area.
Boulevard
A broad, often landscaped roadway, usually in an urban area.
Divided Highway
A multi-lane roadway with curbed or barrier median, or a median that is 4 feet or wider.
Expressway
A divided highway for through traffic with full or partial access control and including grade separation at all or most intersections.
Freeway
An expressway with full access control.
Parkway
A highway that has full or partial access control, is usually located within a park or ribbon of park-like areas, and prohibits commercial vehicles.
Street
A road, usually in a city or town that is wider than an alley and provides non-controlled access.
Turnpike
A toll road or one formerly maintained as such.
ROUTE
Definition: A designated, nonbranching path through a transportation network.
Spatial Presentation: Traversal
RUNWAY
Definition: A straight path on land used for the take-off and landing of aircraft.
Spatial Presentation: Line, Area, Image
TERMINAL
Definition:An area or enclosed structure that is used to load or unload passengers or cargo or to transfer them between different vehicles on the same transportation modal network. See: Intermodal Transportation Facility
Spatial Presentation: Point, Area
Related Terms:
Railway Classification Yard
An area provided with a system of tracks and associated structures, where railway trains are assembled, and railway cars are switched, stored, or serviced.
Station
A building used to load or unload or transfer passengers or cargo from a motor bus or railroad.
Tipple
A central facility for the loading or unloading of coal for transportation by rail or truck.
TRAIL/PATH
Definition: Structures and properties that are used to support the operation and maintenance of a transportation mode.
Spatial Presentation: Point, Area
Related Terms:
Harbor Facility/Port Facility
Those facilities including buildings, structures, equipment, passageways, or parking areas that are located along or adjacent to a harbor or port and provide services to watercraft such as places to anchor or dock, to load or unload passengers or cargo, and to repair and store vessels. Harbor facilities/port facilities can include the following: anchorage; berth; dock; drydock; launching ramp; marina; mooring; pier; loading tramways; pump out facility; shipyard and wharf/quay.
Pipeline Facility
Those facilities including buildings, structures, and equipment, that are used in the transportation and storage of gas or hazardous fluids, or in the treatment of these products during the course of transportation. Pipeline facilities can include the following: blocking valve, liquefied natural gas (LNG) facility, pressure pump station, production facility, and refinery.
Railway Facility
Those facilities including buildings, structures, equipment, passageways, or parking areas that are located along or adjacent to a railway and provide housing and maintenance services to locomotives. Railway maintenance facilities can include: car shop repair track area; round house; switch; and, turntable.
Roadway Facility
Those facilities including buildings, structures, equipment, passageways, or parking areas that are located along or adjacent to a roadway and provide motorist services, regulatory maintenance, or administrative functions. Roadway facilities can include overlooks, parking areas, rest sites, toll booths, traffic inspection facilities, and, weigh facilities.
Transit Facility
Those facilities including buildings, structures, equipment, passageways, or parking areas that are dedicated to the operations and maintenance of transit service. Transit facilities can include bus and rail maintenance shops, storage yards, maintenance-of-way buildings and yards, and marshaling yards.
TRANSPORTATION FACILITY
Related Terms Continued:
Waterway Facility
Those facilities including buildings,structures, equipment, roads, walks, passageways, or parking lots that are located along or adjacent to a waterway and provide safety services, regulatory maintenance, or administrative functions. Waterway facilities can include: buoys, ice piers, lighthouses, LORAN transmitters, roundabouts, safety landings, and turning basins.
TRANSPORTATION SYSTEM
Definition: A dedicated right-of-way that is used exclusively by transit vehicles specially equipped for travel on the guideway.
Spatial Presentation: Line, Traversal