Terms and Definitions

Intro

In order to understand the common vocabulary which you will encounter when developing MAP and SPaT messages, one has the draw from several different subject areas; often with shared names for conflicting terms.

  • DSRC messages and the ITS industry
  • General GIS practices
  • MAP and SPaT terminology defined by J2735
  • Traffic Engineering terminology for signal controllers, both in the US and abroad

The following Terms and Definitions are provided to help you.  Note that where various standards are concerned these terms may often have normative meaning.  In other words, you have to do it that way in order to comply with the standard.

SPAT vs SPaT

The capitalization question still comes up, so let’s deal with it here.  There is no hard right or wrong on this one.

Historically, all SAE DSRC messages are given abbreviation which are in all caps, as in BSM, MAP< SPAT, etc.  This comes from the ASN and XML syntax and style rules that are used in the work. That is why full caps are used in the actual ASN and XML of the standard and in places (such a J2735) where it is very clear it the message structure itself that be being referred to.

The phase “signal phase and timing” has existed among traffic engineers for decades.  The larger community of ITS still stumbles over the precise meaning of phase vs movement, and the fact that the SPAT message coveys timing information on the whole movements does not help in this regard.  The earliest known use of “SPaT”  come from folks working at Turner-Fairbank Highway Research Center in Washington who coined the term for work that predated and feed the SAE DSRC standards process.  They also used the term “GID” for what is no called MAP.  Several others were also working in this area, but TFHRC get the nod for being first.

We recommend that you use the capitalization of SPaT and the general phase of MAP-SPaT except when referring to the actual ASN message in which case all caps would be used.

So that’s your ITS history lesson for the day.

Subject Matter Notes

When a term is unique to given body or work, or to a vendors use and meaning, we try to note that by the use of a color-coded keyword at the end of the entry. For example DSRC message set work, published by the SAE, is denoted with this symbol:  [DSRC]  while the work of IETF by the GeoJSON group uses: [GJSN]


The Terms

Note: This section is in-work, and at this point the term listed are just in a holding pattern as more are added.  Please suggest further terms as you read / review these pages.

 

*.PRJ  file type

*.shp file type

Add ref to terms in J2735

Approach

Base Map

Chart

Coordinate System

CRS

*.CSV file type

Datum

Delimited  (as in referring to a flat file for importing, see *.csv etc)

Delta Point

Delta_Node

DEM  (Digital Elevation Map)

DGPS

DSRC

Fixed/Float

GeoJSON

GIS

GNSS

GPS

JSON

Lane

Lane Level Accuracy

Lane Object

Layer(s)

LLH

Map Engine

MAP?

Node

OBU

Offset

Offset

Phase

*.PNG file type

Point

Poly Line

QGIS

Rectification

RSU

RTK

Shape File

Shapefiles

Split Phase

*.TIFF file type

*.TSV file type

WGS-84

XYZ

 

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