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5.6 Vector Modules

The vector modules are designed for the transfer of vector data as objects; that is, each module record defines a vector object including links to its component parts as well as a possible direct link to its attribute data.

The vector objects of 2.3 have been grouped into corresponding modules according to the similarity in data fields required to represent the object.

Aside from attributes, the modules that implement the vector-based spatial objects are: Point-Node, Line, Arc, Ring, Polygon, and Composite.

As more than one type of object can be stored in each type of module, the type of object represented is expressed through an object representation code. Table 34 summarizes the assignment of vector-based objects to modules and lists the object representation code for each.

The vector-based spatial objects may include both the downward "is composed of" definition in the composite module and the upward "composes" definition in the Point-Node, Line, Arc, Ring, and Polygon modules.

5.6.1 Point-Node Module

The Point-Node module must be used to transfer points of the following type: generic point, entity point, label point, area point, and node (see Table 35).

5.6.2 Line Module

The Line module must be used to transfer spatial objects of the following type: string, link, complete chain, area chain, and network chain (both planar and nonplanar) (see Table 36).

When the object type is that of a chain (LE, LL, LW, or LY), the Chain Component ID field may be used instead of or in addition to the Spatial Address field. The Chain Component ID then refers to records in other Line or Arc modules.

This allows for the transfer of a chain entirely composed of arcs, or a chain made up of a mixture of arcs and strings.

Table 33 - Composite module specification

FIELD NAME	SUBFIELD NAME	FIELD/SUBFIELD DESCRIPTION	TYPE	DOMAIN	DOMAIN DESCRIPTION	MNEMONIC
Composite (P) [M]						COMP
	Module Name [M]	A unique identifier for the module.	A	Alphanum	Name must begin with an alphabetic character other than SPACE.	MODN
	Record ID [M]	Composite object record identifier.	I	Integer	Unsigned integer; with Module Name must form unique ID within the file set.	RCID
	Object Representation [M]	Representation code for the object.	A	FF	A constant value of "FF" for composite objects.	OBRP
(^)Attribute ID (R)		Foreign identifier for Attribute Primary module record.				ATID
(^)Foreign ID (O)		Foreign identifier of module record for object that is a part of this composite. The order of the instances of this field is significant when referencing linear objects; the order indicates the sequence of construction of the composite object in terms of its component objects.				FRID
(^)Composite ID (R)		Foreign identifier of Composite module record that includes this composite object.				CPID

Table 34 - Modules and vector-based object representations

Module type	Object representation	Representation Code
Point-Node	Point	NP
	Entity point	NE
	Label point	NL
	Area point	NA
	Node, planar graph	NO
	Node, network	NN
Line	String	LS
	Link	LQ
	Complete chain	LE
	Area chain	LL
	Network chain, planar graph	LW
	Network chain, nonplanar graph	LY
Arc	Circular arc, three point center	AC
	Elliptical arc	AE
	Uniform B-spline	AU
	Piecewise Bezier	AB
Ring	Ring with mixed composition	RM
	Ring composed of strings	RS
	Ring composed of chains	RU
	Ring composed of arcs	RA
Polygon	G-polygon	PG
	GT-polygon composed of rings	PR
	GT-polygon composed of chains	PC
	Universe polygon composed of rings	PU
	Universe polygon composed of chains	PW
	Void polygon composed of rings	PV
	Void polygon composed of chains	PX

Table 35 - Point-node module specification

FIELD NAME	SUBFIELD NAME	FIELD/SUBFIELD DESCRIPTION	TYPE	DOMAIN	DOMAIN DESCRIPTION	MNEMONIC
Point-Node (P) [M]						PNTS
	Module Name [M]	A unique identifier for the module.	A	Alphanum	Name must begin with an alphabetic character other than SPACE.	MODN
	Record ID [M]	Point object record identifier.	I	Integer	Unsigned integer. With Module Name must form unique ID within the file set.	RCID
	Object Representation [M]	Representation code for the object.	A	NP NE NL NA NO NN	Point Entity point Label Point Area Point Node, planar graph Node, network	OBRP
(-)Spatial Address (N) [M/NP|NE|NL|NA]		Spatial address of point (single spatial address).				SADR
(^)Attribute ID (R) [M/NL]		Foreign identifier for Attribute Primary module record.				ATID
(^)Line ID (O) [X/NP|NE|NL|NA]		Contains foreign identifier of line associated with the node. The required ordering for the instances of this field relates to the occurrence of adjacent lines around the node.				LNID
(^)Area ID (O) [X/NP|NN]		Contains foreign identifier of area or polygon associated with the node, area point, label point, or entity point. The required ordering for the instances of the field relates to the occurrence of adjacent areas around the node.				ARID
(^)Composite ID (R)		Contains foreign identifier of Composite module record that includes this Point-Node.				CPID
(^)Representation Module ID (O)		Contains foreign identifier of the Representation module record.				RPID
(-)Orientation Spatial Address (O) [X/NP|NE|NA|NO|NN]		Spatial address of orientation point. This point combined with the location point determines the angle of the text string. If omitted, the text string is placed horizontally. If more than one point is provided, then these points combined with the location point define a curve along which the text string is placed. If a total of three points are provided, the location point is the start point of the circular arc. The first orientation point is an intermediate point on the circular arc between the location point and the second orientation point, which lies on the circular arc. If more than three points are provided, the arc is defined as a second order piecewise Bezier arc.				OSAD
(^)Attribute Primary Foreign ID (O) [X/NP|NE|NA|NO|NN]		Contains foreign identifier of the Attribute Primary module record that includes the attribute to be annotated.				PAID
	(N)Attribute Label (O) [X/NP|NE|NO|NN]	Name of attribute subfield to be annotated.	A	Gr-chars	Attribute subfield name as in the Attribute Primary and Secondary modules.	ATLB
(-)Symbol Orientation Spatial Address (N) [X/NL]		Spatial address of orientation point (single spatial address). This point combined with the location point determines the angle of symbol representing the point. If omitted, the symbol is placed horizontally.				SSAD
(continued)

Table 36 - Line module specification

FIELD NAME	SUBFIELD NAME	FIELD/SUBFIELD DESCRIPTION	TYPE	DOMAIN	DOMAIN ESCRIPTION	MNEMONIC
Line (P) [M]						LINE
	Module Name [M]	A unique identifier for the module.	A	Alphanum	Name must begin with an alphabetic character other than SPACE.	MODN
	Record ID [M]	Line object record identifier.	I	Integer	Unsigned integer. With Module Name must form unique ID within the file set.	RCID
	Object Representation [M]	Representation code for the object.	A	LS LQ LE LL LW LY	String Link Complete chain Area chain Network chain, planar grph Network chain, nonplanar	OBRP
(^)Attribute ID (R)		Foreign identifier for Attribute Primary module record.				ATID
The following two fields are to be used for complete and area chains (object representation codes LE and LL) and must reference the topologically correct GT-Polygons (see 2.3.4.5.2, Two-dimensional Manifold).
(^)Polygon ID Left (N) [M/LE|LL][X/LS|LW|LY|LQ]		Foreign identifier of left Polygon or Area Point module record.				PIDL
(^)Polygon ID Right (N) [M/LE|LL][X/LS|LW|LY|LQ]		Foreign identifier of right Polygon or Area Point module record.				PIDR
The following two fields are to be used for links and for complete and network chains (object representation codes LQ, LE, LW and LY) and must reference the topologically correct nodes (see 2.3.4.5, graph).
(^)Startnode ID (N) [M/LE|LW|LY|LQ][X/LS|LL]		Foreign identifier of start node Point-Node module record.				SNID
(^)Endnode ID (N) [M/LE|LW|LY|LQ][X/LS|LL]		Foreign identifier of end node Point-Node module record.				ENID
(^)Chain Component ID (O) [X/LS|LQ][O/LE|LL|LW|LY/Spatial Address]		Foreign identifier of module record of other Arc or Line module. The order of the instances of this field indicates the sequence of construction of the chain composed of arcs, or of strings and arcs.				CCID
(-)Spatial Address (O) [M/LS] [X/LQ] [O/LE|LL|LW|LY/Chain Component ID]		Spatial address of line point. The order of the instances of this field indicates the construction of the line in terms of vertices. Note that even if the line module record includes foreign identifiers of the nodes (for chains and links), the spatial addresses of the nodes, although redundant, must be included here.				SADR
(^)Composite ID (R)		Foreign identifier of Composite module record which includes this line.				CPID
(^)Representation Module ID (O)		Contains foreign identifier of the Representation module record.				RPID
(continued)

5.6.3 Arc Module

An Arc module must be used to transfer the arc object as defined in 2.3.2.3. Arc modules are used to transfer only the geometry of the curved line and rudimentary attributes (see Table 37). If topology is required, then a chain must be used to reference the appropriate Arc module record, and the topology must be associated with the chain object.

An Arc module must be used to transfer arcs of the following types:

	AC	Circular arc
	AE	Elliptical arc

and other curves of the following types:

	AU	Uniform B-Spline
	AB	Piecewise Bezier

For both circular and elliptical arcs, the start and end addresses must occur in counterclockwise order. Total sweep angle for circular arcs and elliptical arcs must be less than or equal to 360 degrees.

For circular arcs, radius and start vector are defined by the start address. Arcs with a sweep angle of 360 degrees have the same start and end addresses.

The Order subfield must not be used with circular arcs or elliptical arcs.

All parametric descriptions must apply only to the horizontal components of the spatial address. All other components may be encoded; however, these components must be ignored in reconstructing objects based on these descriptions.

5.6.4 Ring Module

The Ring module must be used to transfer the ring object as described in 2.3.2.6. A ring is defined to consist of either strings, arcs, or chains, which are one-dimensional line objects. However, four types of chains can be represented in the Line module, and arcs can be referenced directly, or indirectly as components of chains (see Table 38). The Object Representation Codes for Rings are "RM" for a ring of mixed composition, "RS" for a ring of strings, "RU" for a ring of chains (any type), and "RA" for rings directly composed of arcs. Because strings, arcs, and chains are all stored in the Line module or can be referenced through the Line module, the composition of a Ring is primarily expressed as a sequence of Line foreign identifiers. But Rings can be expressed in the form of arcs as well, so that the same foreign identifier field may be used to refer to Arc module records. Because rings are parts of polygons that themselves can be linked to attributes, there is no forward attribute link provided in this module.

5.6.5 Polygon Module

The Polygon module must be used to transfer polygons as defined in 2.3.3. There are two types of polygons: G-polygons, and GT-polygons. Geometry only polygons (G-polygons) consists of one outer ring, and zero or more inner rings. This module therefore contains a secondary field that is a foreign identifier for its member rings. The order of the rings is significant. The outer ring must occur first, followed by the inner rings, if any (see Table 39).

The geometry-topology polygons (GT-polygons) can also be transferred in terms of constituent rings, but an alternative is to use chains instead of rings. For this purpose the module has a secondary field that is a foreign identifier for its member chains. The order of the chains is significant but is not specified. Either one or the other method may be used, so that in a given module either the Ring ID field or the Chain ID field may be present, but not both. When rings are used for GT-polygons, the ordering requirements are the same as for G-polygons.

.

Table 37 - Arc module specification

FIELD NAME	SUBFIELD NAME	FIELD/SUBFIELD DESCRIPTION	TYPE	DOMAIN	DOMAIN DESCRIPTION	MNEMONIC
Arc (P) [M]						ARC
	Module Name	A unique identifier for this Arc module.	A	Alphanum	Name must begin with an alphabetic character other than SPACE.	MODN
	Record ID	Arc object record identifier.	I	Integer	Unsigned integer; with Module Name must form unique ID within the file set.	RCID
	Object Representation	Representation code for the object.	A	AC	Circular arc, three point center.	OBRP
				AE	Elliptical arc.
				AU	Uniform B-spline.
				AB	Piecewise Bezier.
	Surface	Indicates the type of surface on which the reconstruction must take place.	A	PLAN	PLANAR; reconstruction of arc occurs only on a planar surface.	SRFC
				ELIP	ELLIPSOIDAL; reconstruction of arc occurs on an ellipsoidal surface.
	Order [X/AC|AE]	Value of the largest exponent in the parametric expression.	I	Integer	<9, positive value indicating the value of the largest exponent in the parametric expression.	ORDR
(-)Arc Address (N) [M/AC|AE] [X/AU|AB]	The following field contains three spatial addresses, either six (if x,y) or nine (if x,y,z) subfields					ARAD
	(-)Center Address	Spatial address of the center point of the arc.				CTAD
	(-)Arc Start Address	Spatial address of the start point of the arc and also defining the start vector.				STAD
	(-)Arc End Address	Spatial address of the end point of the arc and also defining the end vector.				ENAD
Ellipse Address (N) [M/AE] [X/AC|AU|AB]						ELAD
	(-)Conjugate Diameter Point - Major Axis	Spatial address of a point on the major axis and the ellipse.				MJRA
	(-)Conjugate Diameter Point - Minor Axis	Spatial address of a point on the minor axis (placed perpendicular to the major axis) and the ellipse.				MNRA
(-)Curve Address (O) [M/AU|AB] [X/AC|AE]		Spatial address for control points on curve.				CADR
(^)Attribute ID (R)		Foreign identifier for Attribute Primary module record				ATID
(^)Composite ID (R)		Foreign identifier of composite module record which includes this arc.				CPID
(^)Representation Module ID (O)		Contains foreign identifier of the Representation module record.				RPID
(continued)

Table 38 - Ring module specification

FIELD NAME	SUBFIELD NAME	FIELD/SUBFIELD DESCRIPTION	TYPE	DOMAIN	DOMAIN DESCRIPTION	MNEMONIC
Ring (P) [M]						RING
	Module Name [M]	A unique identifier for the module.	A	Alphanum	Name must begin with an alphabetic character other than SPACE.	MODN
	Record ID [M]	Ring object record identifier.	I	Integer	Unsigned integer; with Module Name must form a unique ID within the file set.	RCID
	Object Representation [M]	Representation code for the object.	A	RS RU RA RM	Ring of strings. Ring of chains. Ring of arcs. Ring of mixed composition.	OBRP
(^)Line or Arc Foreign ID (O) [M]		Foreign identifier of Line or Arc module record for line or arc object as part of the ring. The order of the instances of this field indicate the sequence of construction of the ring in terms of its line in a clockwise direction with reference to the interior of the ring.				LAID
(^)Polygon ID (R) [M]		Foreign Identifier of a polygon of which the ring is a part.				PLID

Table 39 - Polygon module specification

FIELD NAME	SUBFIELD NAME	FIELD/SUBFIELD DESCRIPTION	TYPE	DOMAIN	DOMAIN DESCRIPTION	MNEMONIC
Polygon (P) [M]						POLY
	Module Name [M]	A unique identifier for the module.	A	Alphanum	Name must begin with alphabetic character other than SPACE.	MODN
	Record ID [M]	Polygon object record identifier.	I	Integer	Unsigned integer; with Module Name must form unique ID within the file set.	RCID
	Object Representation [M]	Representation code for the object.	A	PG PR PC PU PW PV PX	G-Polygon. GT-Polygon, rings. GT-Polygon, chains. Universe polygon, rings. Universe polygon, chains. Void polygon, rings. Void polygon, chains.	OBRP
(^)Attribute ID (R)		Foreign identifier for Attribute Primary module Record.				ATID
(^)Ring ID (O) [M/PR][X/PC]		Foreign identifier of Ring module record for ring object as part of the polygon. Order is significant, the outer ring must be referenced first.				RFID
(^)Chain ID [X/PR|PU|PV]		Foreign identifier of Line module record for chain object as part of the polygon. Order is significant, but not specified.				CHID
(^)Composite ID (R)		Foreign identifier of Composite module record that includes this polygon.				CPID
(^)Representation Module ID (O)		Foreign identifier of the Representation module record. This representation module refers to the area fill representation. The boundary is represented via the line object.				RPID