string

boolean

integer

double

anyURI

gpml:featureId

• GPML Feature Ids are the unique identifiers used for anything with a gpml:featureId[1] identity property, i.e. anything that derives from gpml:AbstractFeature. They must be unique for every feature, generated at creation time and remain unchanged for the lifetime of the feature.
• As an example, the unique id process used by GPlates draws from several sources of uniqueness, including Local time, Internal incrementing integer from this session, User id, Hostname, and Process Id. For example: GPlates-2263390205.0-jboyden.aurora.28095. Note that this is only an example of the process GPlates uses to create a unique identifier - the GPGIM only specifies that the id must be unique and remain constant for every gpml:Feature.
• The final featureId string should be restricted to the characters that are acceptable for XML Ids: http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/#Id

gpml:revisionId

• GPML Revision Ids are the unique identifiers used for the specific revisions of gpml:AbstractFeatures. They must be unique for each revision, generated at revision creation time.
• The final revisionId string should be restricted to the characters that are acceptable for XML Ids: http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/#Id

gpml:plateId

• Unique Id for a group of features that rotate in unison. Used in all ReconstructableFeatures via the .reconstructionPlateId property. See also TotalReconstructionSequence and AbsoluteReferenceFrame. They are represented by an unsigned long integer.

xs:any

gml:Point

gml:TimeInstant

gml:TimePeriod

gml:LineString

• gml:LineString is here as a placeholder only; in the GML schemas, properties such as centerLineOf will use gml:_Curve, although we expect to be dealing with LineStrings primarily.
• Note that the GPGIM is not GPML; The primary purpose of this document is to be the information model for GPlates, but not get tied down to one particular implementation of that model (e.g. XML, C++). Hence, it does not authoritatively talk about structures external to the GPGIM.

gml:Vector

gml:Polygon

gpml:measure

• maps to gml:MeasureType, which extends double and adds the requirement for a uom attribute indicating the units used.

gpml:angle

• represents an angle measurement. maps to gml:MeasureType, which bestows the ability to use the uom= attribute on the property, which in this case will likely be (degrees)

gml:_MetaData

gml:_Geometry

gml:AbstractFeature

• Note: all the properties listed here are for convenience only; we inherit many properties upstream from GML, useful things like gml:name and gml:description. There are many more that are not listed here which may come in handy.
• For example, there are two attributes (not properties) which will be essential for GPlates:
• srsName= For indicating the geocentric/geodetic ellipsoid approximation of the earth, for the coordinates used by geometry of this Feature- i.e. WGS84.
• frame= For indicating the geological time scale that was used to determine temporal position of this Feature. I believe we'll actually be using the 'frame=' attribute in gml:TimePeriod.{begin,end} or gml:TimeInstant.timePosition

• contains external gml:_MetaData[0..*] gml:metaDataProperty
  • The gml:metaDataProperty can contain almost completely arbitrary markup, thanks to the use of <xs:any>.
• contains external string[0..1] gml:description
  • Again, a 'hidden but useful' property inherited from GML.
• contains external string[0..*] gml:name
  • More than one gml:name can be assigned, the distinction between two names being handled by the 'codeSpace=' attribute of gml:name.
  • gml:name is actually found in the gml:AbstractFeatureType side of things, I just include it here so these 'hidden but useful' properties can be shown.

gml:AbstractFeatureCollection

gml:AbstractMetaData

gml:AbstractGeometry

FeatureCollection

- This is the root element for GPML data files, and is the way GML groups all other Features together. It contains these features via the gml:featureMember property.

• contains external AbstractFeature[0..*] gml:featureMember
  • We inherit a property similar to this from gml:AbstractFeatureCollection. In the case of GPML we will be filling it with anything that derives from gpml:AbstractFeature, although there's nothing stopping other GML-compliant features from being bundled up with our own.

AbstractFeature

- Highest-level abstract parent of all GPML Features.

• contains const gpml:featureId[1] identity
  • GPlates enforces a mandatory unique Id for each Feature. See gpml:featureId for more information.
  • gml:name with a specific codespace was considered, but in this case we want to ensure specific Features have such an Id.
• contains const gpml:revisionId[1] revision
  • All GPlates Features also have a revision Id. When a feature is modified by a user, it gets a new revision Id, and its list of superseded revisions is updated. This way we can do some important book-keeping to help us in situations where multiple feature collections are loaded/modified/saved/unloaded.
• contains gpml:revisionId[0..*] supersededRevision
  • This lists all revisions of this feature that were superseded by this one. This is a more accurate way of keeping track of the past, older revisions of a feature.
  • It will be purged on occasion to ensure files do not get bloated from many small changes. Newly superseded revisionId s get unshifted onto the front/head of the list, older ones are at the end/tail of the list.
  • a simple linear 'version number' would fail if a feature collection was concurrently modified by multiple users and then merged.
• contains OldPlatesHeader[0..1] oldPlatesHeader
  • Since a Feature in GPML will often correspond to a PLATES polyline (if a PLATES file was the original source of data), we include an optional reference to a Plates-compatible header object. This is used to keep metadata around if we import from a PLATES data file.
• contains string[0..*] subcategory
  • Every gpml:Feature can optionally have one or more subcategories assigned to it. These are free-form text strings, and behave very similarly to the gml:name property; they also possess a 'codeSpace=' attribute to indicate what convention was used when assigning this subcategory to this Feature.
  • Use of the .subcategory property is entirely optional, however it is useful in several situations. There are many possible subcategories of real-world:Features, and these are highly subjective, depending on scientist, dataset, and area of research. Permitting arbitrary subcategorisation in the GPGIM has two benefits. One, GPlates can to continue to treat those real-world:Features as the appropriate gpml:Feature since any subcategory must have the same properties as the parent gpml:Feature. Two, it allows the scientist to have a finer grain of control over the categorisation of those real-world:Features without messing around with XML trying to extend the GPGIM.
  • An example: Seamount s and Guyot s. A Guyot is a special case of Seamount with a flat top. Functionally, they are identical. A problem arises; do we create a GPGIM feature for both of them, or just use Seamount for both cases? Some scientists and datasets may not care about the distinction, and wish to treat everything as a gpml:Seamount without being forced to go over the data and classify everything. On the other hand, a "Guyot Expert" would be very interested in the distinction between the two. The .subcategory property allows you to do this, without forcing you to.

TimeVariantFeature

• TimeVariantFeature is one of the parents to the majority of commonly used gpml:Features.
• Most, but not all, features will ultimately inherit from our gpml:TimeVariantFeature in order to have the .validTime property. In contrast, features deriving from InstantaneousFeature require a TimeInstant rather than a TimePeriod, and they obtain this via the .reconstructedTime property.

• contains gml:TimePeriod[0..1] validTime
  • The validTime parameter defines the position of this feature on the geological timescale.
  • Some Features may only exist between (say) 120Ma and 100Ma, others will be represented as a series of distinct Features, i.e. a MidOceanRidge at (lat,long) between 200Ma-160Ma and another MidOceanRidge (which happens to model the same physical thing) at (lat,long) between 160Ma-0Ma, perhaps due to it having radically different properties. Generally, it is preferable to use GPML's time-dependent properties where applicable, but since we will be importing PLATES data, this 'slicing' of features will be commonplace in real datasets.
  • Note that if a gpml:Feature is a ReconstructableFeature, it might potentially have more gml:TimePeriod s recorded in its .reconstructionPlateId property, as it is a time-dependent property. The validTime that we specify here should still be used as the master indication of the Feature's lifetime.

InstantaneousFeature

- "Snapshot" version of GPML Features, defined at a specific time

• Most of the ReconstructableFeature tree is copied here. Instantaneous versions of gpml:Features are designed for export to other programs, which would have difficulty doing reconstructions themselves.
• These features have different properties to their Reconstructable counterparts. Aside from the "big one" of not being rotatable via the action of Finite Rotations, their geometry is defined in terms of a specific time (.reconstructedTime) rather than being defined in present-day terms. This distinction also becomes more important with time-variant property values.
• In comparison to ReconstructableFeature:-
• - must be defined for only an instant.
• - must have its geometry specified in its time-of-definition position (the time-of-definition may or may not be the present-day)
• - will not have a gpml:reconstructionPlateId
• Note, No properties of an InstantaneousFeature will be time-dependent!
• Like ReconstructableFeature, InstantaneousFeatures should have at least one geometric presence.
• As InstantaneousFeatures do not have a reconstruction plate ID property, they will be given a default reconstruction plate ID of 0 for display purposes.

• contains FeatureSnapshotReference<TimeVariantFeature>[0..1] derivedFrom
  • an optional link to the ReconstructableFeature this Instantaneous snapshot was taken from, for historical interest.
• contains gml:TimeInstant[0..1] reconstructedTime
  • the TimeInstant corresponding to the moment this InstantaneousFeature was converted from its Reconstructable original.
  • Normal GPlates Features store their geometry in present-day coordinates, and store reconstruction information to rotate them into paleo-coordinates. However, for exporting data into other GPML aware programs, i.e. GMT, it is necessary to do the rotations on behalf of the external application. The .reconstructedTime property of the Instantaneous feature records what time this Feature was reconstructed to by GPlates, (in Ma or whatever 'uom' and 'frame' you want in the TimePeriod).
• contains gml:TimePeriod[0..1] validTime
  • Instantaneous features only really exist for a single instant, the TimeInstant in the reconstructedTime property, set when a snapshot is made of a ReconstructableFeature. The 'TimePeriod validTime' property of the ReconstructableFeature is no longer applicable.
  • However, the original information about the features' lifespan is still useful information. Isochrons in particular measure their age as their time-of-appearance. This information would be lost in InstantaneousIsochron snapshots unless the information is copied to this .validTime property.
  • This property may at first glance appear to be identical to TimeVariantFeature.validTime, and it is true that the value of this property should be the same; however it serves a different purpose (useful record of original data) and is in fact an entirely different .validTime property with a TimePeriod value.
• contains gpml:plateId[0..1] reconstructedPlateId
  • in the spirit of not throwing away information, the plateId at time of conversion to an InstantaneousFeature type is recorded here. Unlike ReconstructableFeature.reconstructionPlateId, this is not a time-dependent property, and will only ever refer to one gpml:plateId.

ReconstructableFeature

- Parent of all GPML Features we may want to associate with a plateId and are reconstructable.

• A ReconstructableFeature may be rotated relative to another ReconstructableFeature by the action of Finite Rotations (Inside a TotalReconstructionSequence)
• In comparison to InstantaneousFeature:-
• - might be defined for only an instant
• - must have its geometry specified in its present-day position
• - must have a gpml:reconstructionPlateId
• ReconstructableFeatures should have at least one geometric presence.

• contains ConstantValue<gpml:plateId>[1] reconstructionPlateId
  • The plateId to use for reconstruction purposes. This property is a time-dependent one, but presently only supports a ConstantValue gpml:plateId.
  • In future releases, this is expected to be expanded to use a PiecewiseAggregation of multiple ConstantValues rather than a single ConstantValue, allowing different gpml:plateIds to be used varying through time.
  • Any feature which does not have a reconstruction plate ID property will be given a default reconstruction plate ID of 0. This will affect InstantaneousFeatures, and any other features, which don't have reconstruction plate IDs, whose geometries should be displayed.
  • Time-Dependency: Will later become a PiecewiseAggregation<gpml:plateId>.
• contains FeatureReference<ReconstructableFeature>[0..*] truncatedSection
  • Optional references to other Features that the user has indicated are supposed to be the same feature. While GPlates will treat each individual gpml:Feature separately, it is intended as a reminder that this Feature is part of a larger whole.
  • A common problem in PLATES datasets is the lack of any deformable geometry. This is often hacked around by creating multiple 'features' for the same real-world thing, for example, an Isochron getting subducted might have have been 'cut up' into multiple PLATES 'IS' features, to simulate the Isochron slowly disappearing. One day, this property will be used by a magical algorithm to undo all the 'cutting up' of features done in data sets for the purpose of hacking deformable geometry into PLATES.
  • Another example of this property in use is FractureZone.

TangibleFeature

• An 'Instantaneous' copy of this class exists, InstantaneousTangibleFeature.

ArtificialFeature

• In contrast to TangibleFeature, this deals with geometry that has been arbitrarily created, or possibly derived from a TangibleFeature. For example, InferredPaleoBoundary is a plate boundary that is assumed to have existed, even though it has long since been subducted under the surface. OldPlatesGridMark is a sequence of lines defined in PLATES data files for annotation.
• An 'Instantaneous' copy of this class exists, InstantaneousArtificialFeature.

PropertyDelegate<T>

- Reference to the value of a property belonging to a remote gpml:Feature

• A GPML-specific way to refer to a LineString property inside a Feature. In later versions of PropertyDelegate, this could be an XPath (or the various other X.. technologies) to the LineString itself, or some way to refer to the (Feature + appropriate property name). Most likely, the property we will be interested in referring to is "centerLineOf", but there could be others.
• This is a single tag, and has special properties to point to the feature and property we are interested in.
• This is so we don't paint ourselves into a corner later on. It's completely opaque to GML, and doesn't have quite the same potential for chaos as xlink:href does.

• contains const string[1] valueType
  • The stringified type of geometry, structural type etc that this PropertyDelegate can dereference to, as expressed through the template-like "T" parameter. This template parameter passed to PropertyDelegate from another property is a hint as to what types are expected when dereferencing.
• contains gpml:featureId[1] targetFeature
  • The gpml:featureId that uniquely identifies the gpml:Feature containing the desired property.
• contains string[1] targetProperty
  • Accessing a single property that is the direct child of the .targetFeature is accomplished by setting .targetProperty to the name of the property, such as "centerLineOf"
  • Accessing a nested property inside some complex Structural Type is a little more difficult. PropertyDelegates 1.0 will support a simple XPath-like syntax using "/*/" as a separator to specify the path. Example: "gpml:someProperty/*/gpml:someOtherProperty"
  • In PropertyDelegate 1.0, .targetProperty will start off being supported as a limited subset of an XPath expression.

FeatureReference<T>

- Reference to a remote gpml:Feature

• contains const string[1] valueType
  • The stringified type of Feature that this FeatureReference can dereference to, as expressed through the template-like "T" parameter. This template parameter passed to FeatureReference from another property is a hint as to what types are expected when dereferencing.
• contains gpml:featureId[1] targetFeature
  • The gpml:featureId that uniquely identifies the desired gpml:Feature.

FeatureSnapshotReference<T>

- Reference to a remote gpml:Feature (specific revision)

• Used by InstantaneousFeature to supply a potentially-useful reference to the TimeVariantFeature that the Instantaneous snapshot was taken from.

• contains const string[1] valueType
  • The stringified type of Feature that this FeatureSnapshotReference can dereference to, as expressed through the template-like "T" parameter. This template parameter passed to FeatureSnapshotReference from another property is a hint as to what types are expected when dereferencing.
• contains gpml:featureId[1] targetFeature
  • The gpml:featureId that uniquely identifies the desired gpml:Feature.
• contains gpml:revisionId[1] targetRevision
  • The gpml:revisionId that uniquely identifies the specific revision of the gpml:Feature this FeatureSnapshotReference should resolve to.
  • If the specific revision can not be obtained, this FeatureSnapshotReference will be unresolvable.

OldPlatesHeader

- Metadata that all gpml:Features can have, inherited from old PLATES data files.

• For preserving backwards compatibility and not "throwing away" information, if the original files came with PLATES header info, we can include them here and reference them in each AbstractFeature that is associated with that original PLATES file.
• see http://gplates.fn.com.au/trac/wiki/PlatesLineFormat for the full description.
• Rather than use the traditional gml:.metaDataProperty path, I'm making this a seperate entity, if we want to do the full blown GML meta data thing later, there's nothing stopping us, but a simple solution for now is just to have it as an optional property in every AbstractFeature.
• It isn't immediately obvious if this structure should inherit from anything, I'm just making a stand alone structural type, it inherits from nothing in particular and is only used in AbstractFeature. This should make things reasonably simple when GPlates is looking for any PLATES fields.

• contains integer[1] regionNumber
  • 2-digit integer
• contains integer[1] referenceNumber
  • 2-digit integer
• contains integer[1] stringNumber
  • 4-digit integer
• contains string[1] geographicDescription
  • ASCII string, no specified character length
• contains integer[1] plateIdNumber
  • 3-digit integer
• contains double[1] ageOfAppearance
  • 6 char, 1 d.p float number, in Ma
• contains double[1] ageOfDisappearance
  • 6 char, 1 d.p float number, in Ma
• contains string[1] dataTypeCode
  • ASCII string, 2 characters
• contains integer[1] dataTypeCodeNumber
  • 4-digit integer
• contains string[1] dataTypeCodeNumberAdditional
  • ASCII string, 1 character
• contains integer[1] conjugatePlateIdNumber
  • 3-digit integer
• contains integer[1] colourCode
  • 3-digit integer
• contains integer[1] numberOfPoints
  • 5-digit integer, number of points (not counting the final "terminator" point (99.0000,99.0000))

TimeDependentPropertyValue<T>

- Abstract parent of all structural types handling time-dependency for property values.

• contains const string[1] valueType
  • The stringified version of the template-like "T" parameter. The template parameter passed to a TimeDependentPropertyValue will be stringified and put in the valueType property, to record what type this TimeDependentPropertyValue will store.

ConstantValue<T>

- Most basic case of TimeDependentPropertyValue

• contains T[1] value
  • The ConstantValue time-dependent value needs to be very flexible regarding what it can hold. So we use "T" like a 'C++ template' or 'generic' type.
• contains string[0..1] description
  • Annotation property; as the other time-dependent-property terminator, ConstantValue deserves a description field as much as TimeSample does.

IrregularSampling<T>

- TimeDependentPropertyValue combining samples and an interpolation function

• contains TimeSample<T>[1..*] timeSample
  • The values and associated time instants that are to be used, and interpolated as necessary.
• contains InterpolationFunction[0..1] interpolationFunction
  • The method to use to interpolate between TimeSlices.

TimeSample<T>

- Single TimeInstant with an associated value.

• Used in IrregularSampling time dependent property values, e.g. SlerpInterpolation, to provide the data points to interpolate between.

• contains T[1] value
  • The TimeSample time-dependent value needs to be very flexible regarding what it can hold. So we use a 'C++ template' or 'generic' type, T.
• contains gml:TimeInstant[1] validTime
  • The time instant associated with this sample value.
• contains string[0..1] description
  • Annotation property; this will be most useful to annotate the IrregularSampling of FiniteRotations used in TotalReconstructionSequence, mirroring comments commonly found in PLATES rotation files.
• contains const string[1] valueType
  • The stringified version of the template-like "T" parameter. The template parameter passed to a TimeSample will be stringified and put in the valueType property, to record what type this TimeDependentPropertyValue will store.
• contains boolean[0..1] isDisabled
  • in PLATES rotation files, a common technique is to use a moving plate ID of 999 to "comment out" a line (a single total reconstruction pole within the total reconstruction sequence)
  • However, it *should still remain within the sequence* when the sequence is loaded, it should just be disabled/deactivated/whatever. This boolean allows for this behaviour.

PiecewiseAggregation<T>

- TimeDependentPropertyValue combining several different types of TimeDependentPropertyValue joined by time windows

• contains TimeWindow<T>[0..*] timeWindow
  • These TimeWindows will contain a TimePeriod, plus another TimeDependentPropertyValue - this way we can join several different methods of time-dependency together, such as a ConstantValue followed by a IrregularSampling followed by another ConstantValue.

TimeWindow<T>

- Single TimePeriod with an associated time-dependent property value.

• Used in PiecewiseAggregation time dependent property values to join different methods of time-dependency together with TimeWindows.

• contains TimeDependentPropertyValue<T>[1] timeDependentPropertyValue
  • The TimeSample time-dependent value needs to be very flexible regarding what it can hold. So we use a 'C++ template' or 'generic' type, T.
• contains gml:TimePeriod[1] validTime
• contains const string[1] valueType
  • The stringified version of the template-like "T" parameter. The template parameter passed to a TimeWindow will be stringified and put in the valueType property, to record what type this TimeDependentPropertyValue will store.

InterpolationFunction

- Abstract parent for various interpolation methods

• used in IrregularSampling to interpolate between TimeSlices.

FiniteRotationSlerp

- Spherical Linear Interpolation function

• This is an interpolation function designed to interpolate between FiniteRotations.
• Referring to it as an empty standalone xml element, instead of some predefined text string, has the advantage that we can add parameters to it later if necessary.
• This will appear in the XML as a simple <gpml:FiniteRotationSlerp /> element, to indicate the type of interpolation desired in the IrregularSampling TimeDependentPropertyValue.

InstantaneousClosedPlateBoundary

- Snapshot closed polygon plate boundary that is pre-reconstructed to a specific instant in time.

• The "Instantaneous" view of a PlateSlab's closed boundary at an instant in time. It is only valid for a specific time, not reconstructable, and the geometry of this boundary is a simple polygon. The coordinates used are paleo-coordinates. Instantaneous features are designed for export to programs that are not able to reconstruct features themselves. This InstantaneousClosedPlateBoundary would most likely have been derived from a ClosedPlateBoundary.

• contains gml:Polygon[1] boundary
  • An instantaneous snapshot of the plate boundary, represented as a polygon using paleo-coordinates.

ClosedPlateBoundary

- Rigid closed polygon plate boundary that can be reconstructed to any time.

• a simple geometric view of a PlateSlab's closed boundary, possibly derived from a TopologicalClosedPlateBoundary. It is reconstructable, and so the polygon is encoded using present-day coordinates. This type of plate boundary might be most useful as a "Grid Mask" for gridded data relating to the plate.
• Some standard properties are very useful for a ClosedPlateBoundary. The .reconstructionPlateId property inherited from ReconstructableFeature will allow us to associate one (or more, potentially) gpml:plateId s with the plate boundary, gml:name can be used to name the plate, and validTime indicates the lifetime of this plate polygon.

• contains TimeDependentPropertyValue<gml:Polygon>[1] boundary
  • A stand-alone, reconstructable image of the plate boundary, represented as a polygon using present-day-coordinates.

InstantaneousClosedContinentalBoundary

- Snapshot closed polygon continental crust boundary that is pre-reconstructed to a specific instant in time.

• Similar (but not identical) to InstantaneousClosedPlateBoundary, but for crust type differences (oceanic-continental). It is only valid for a specific time, not reconstructable, and the geometry of this boundary is represented in paleo-coordinates.
• See also: ClosedContinentalBoundary, TopologicalClosedContinentalBoundary, and PassiveContinentalBoundary.

• contains enumeration ContinentalBoundaryCrustEnumeration[0..1] type
  • type of the crust contained within this boundary: enumeration.
  • = "Continental" : the interior of this boundary is a region of continental crust.
  • = "Oceanic" : the interior of this boundary is a region of oceanic crust.
  • = "Unknown" : the value of this property is officially unknown; there is no information about which type of crust this boundary is defining.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which side of the boundary is continental crust and which is oceanic, only that the boundary exists. The property is unspecified or indeterminate.
• contains enumeration ContinentalBoundaryEdgeEnumeration[0..1] edge
  • .edge is an enumeration:
  • = "InnerContinentalBoundary" : This Closed Continental Boundary defines the Inner edge of the continental boundary (closest to centre of continental crust - note that in the less common case of defining a closed boundary of type=oceanic crust, the "Inner" enumeration still refers to the innermost edge of -Continental- crust.)
  • = "OuterContinentalBoundary" : This Closed Continental Boundary defines the Outer edge of the continental boundary (furthest away from centre of continental crust, closest to oceanic crust - note that in the less common case of defining a closed boundary of type=oceanic crust, the "Outer" enumeration still refers to the outermost edge of -Continental- crust.)
  • = "Unknown" : This Closed Continental Boundary was digitised or imported without any data telling us how the boundary was chosen with regard to inner and outer edges of the continental crust. The value of this property is officially unknown.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which edge of the boundary polygon is represented by this line. The property is unspecified or indeterminate.
• contains gml:Polygon[1] boundary
  • an instantaneous snapshot of the crust boundary, represented as a polygon using paleo-coordinates.

ClosedContinentalBoundary

- Rigid closed polygon continental crust boundary that can be reconstructed to any time.

• Similar (but not identical) to ClosedPlateBoundary, but for crust type differences (oceanic-continental). It can be rotated via the usual reconstruction mechanisms, and the geometry of this boundary is represented in present-day-coordinates.
• See also: InstantaneousClosedContinentalBoundary, TopologicalClosedContinentalBoundary, and PassiveContinentalBoundary.

• contains enumeration ContinentalBoundaryCrustEnumeration[0..1] type
  • type of the crust contained within this boundary: enumeration.
  • = "Continental" : the interior of this boundary is a region of continental crust.
  • = "Oceanic" : the interior of this boundary is a region of oceanic crust.
  • = "Unknown" : the value of this property is officially unknown; there is no information about which type of crust this boundary is defining.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which side of the boundary is continental crust and which is oceanic, only that the boundary exists. The property is unspecified or indeterminate.
• contains enumeration ContinentalBoundaryEdgeEnumeration[0..1] edge
  • .edge is an enumeration:
  • = "InnerContinentalBoundary" : This Closed Continental Boundary defines the Inner edge of the continental boundary (closest to centre of continental crust - note that in the less common case of defining a closed boundary of type=oceanic crust, the "Inner" enumeration still refers to the innermost edge of the -Continental- crust.)
  • = "OuterContinentalBoundary" : This Closed Continental Boundary defines the Outer edge of the continental boundary (furthest away from centre of continental crust, closest to oceanic crust - note that in the less common case of defining a closed boundary of type=oceanic crust, the "Outer" enumeration still refers to the outermost edge of the -Continental- crust.)
  • = "Unknown" : This Closed Continental Boundary was digitised or imported without any data telling us how the boundary was chosen with regard to inner and outer edges of the continental crust. The value of this property is officially unknown.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which edge of the boundary polygon is represented by this line. The property is unspecified or indeterminate.
• contains TimeDependentPropertyValue<gml:Polygon>[1] boundary
  • a stand-alone, reconstructable snapshot of the plate boundary, represented as a polygon using present-day-coordinates.

InferredPaleoBoundary

- Part of a plate boundary defined by hand for real-world geology that no longer exists.

• e.g. the InferredPaleoBoundary between India and Asia that has since been subducted under the Himalaya.
• An 'Instantaneous' copy of this class exists, InstantaneousInferredPaleoBoundary.

• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] unclassifiedGeometry
  • All geometry defined for the feature where the purpose is not given or unclear.
• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] centerLineOf
  • The inferred boundary. This is the default location for imported geometry.
• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] errorBounds
  • An optional error boundary for the feature. Note that we can use LineStrings or Polygons or a combination of both - anything substitutable for gml:_Geometry.

Contour

- Polyline and/or polygon geometry with additional z-value semantics.

• When a specific depth/height/z-value is associated with this geometry via the 'level' property, it can be called a Contour. Otherwise the term 'Extent' is more suitable, but the two share many properties.
• Contours can also have information about the origin of their geometry:
• The most common use for this class will be Bathymetric Contours. These are 'picked' from a Bathymetry grid, and are conours because they follow a particular depth, for example, the "2000m" contour.
• When the 'level' property is omitted, this geometric type can be used for defining the extents of features based on some gridded data, such as a Gravity map, but without implying that all points of the extent share the same elevation.
• There are some standard, commonly used types of Contour, such as Bathymetry or Topography. However, practically any field or gridded data might be used to create contours.
• For example, picking the extent of an extinct IslandArc might be done from looking at a Gravity grid and choosing the outline by hand. There is no specific criteria used, unlike when defining a Contour.

• contains string[0..*] subcategory
  • As this class derives from gml:AbstractGeometryType in order to be substitutable for gml:_Geometry, it cannot inherit the standard gpml:subcategory property. As it is highly useful for contour types, it is defined directly.
  • Suggested Subcategories:
  • = "Bathymetry" : A contour measuring depth of the ocean floor beneath sea level.
  • = "Topography" : A contour measuring height of land above sea level.
  • = "Gravity" : chosen from a Gravity grid.
  • = "Magnetic" : chosen from a Magnetic grid.
• contains string[0..1] description
  • 'description' is for specific notes relating to this particular Contour.
  • since Contour is neither a gpml:Feature nor a gml:Feature, we need to explicitly include support for a free-form text description field.
• contains gml:_Geometry[0..1] outlineOf
  • The geometry of the Contour specifying a closed or partial outline - expected to potentially use gml:MultiGeometry, gml:LineString and gml:Polygon.
  • As this is a geometry type, it makes little sense to define "This is the default location of imported geometry"; this -is- geometry, any importing or default semantics is left up to the parent gpml:Feature.
  • Note on Time-Dependency: Contours will themselves be wrapped up in TimeDependentPropertyValue as appropriate for the containing gpml:Feature's property.
• contains gpml:measure[0..1] level
  • The value or criteria or level that the contour was chosen for. For marine science, which mostly deals with Bathymetric contours, this criteria would be depth : for instance, a depth of 2000m. Above sea level, this would be a Topographic contour, which might still measure the contour level in metres but measures the height as opposed to the depth. It is even conceivable that someone may want to pick out a "Gravity" contour from a gravity grid; the 'level' of the contour might now be measured in mGals, and words like 'height' and 'depth' have little meaning. Hence the rather general name of this property.
  • When this property is absent, it implies missing data for a Contour, or a Contour chosen with no regard to following a specific level (an "Extent")
  • Then why not give it a more abstract name? Because 'Contour' has special meaning to geoscientists and is a favourite 'go-to' word.

AbstractField

- Abstract superclass for various field data, including stand-alone Contours and outlines.

• Assorted contour-like data and (in future releases) gridded data share AbstractField as a parent class.
• Types of contour (and later, gridded) data include: Bathymetry, Topography, Gravimetry, Magnetics, GlobalElevation, OceanicAge, CrustalThickness, DynamicTopography, MantleDensity, HeatFlow, SedimentThickness, Roughness, SpreadingRate, SpreadingAsymmetry, Stress
• This is because all contoured data is picked from a gridded source, and similarly with most stand-alone outline data. In addition, there are many, many types of gridded data that we may wish to use in the future. With most of these types, it still makes sense to be able to pick outlines and contours from the grid - they are useful in many cases.
• The following list derived from some of the actual data files on Maria's filesystem.
• An 'Instantaneous' copy of this class exists, InstantaneousAbstractField.

• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] outlineOf
  • Geometry specifying a closed or partial outline - expected to potentially use gml:MultiGeometry along with gpml:Contour (which will in turn use more gml:_Geometry - gml:LineString and gml:Polygon in particular). This is the default location for imported geometry.
  • Time-dependent, because although rotatable shifting deforming contours through time sounds like a mouthful, Simula has an interest in this and we should leave the door open.

Bathymetry

- Sea floor depth data, including bathymetric contours and grids.

• Usually measured in m (depth)
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousBathymetry.

Topography

- Elevation data, including topographic contours and grids.

• Usually measured in m (height)
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousTopography.

Gravimetry

- Gravity grids, outlines, and contours.

• Usually measured in mGal
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousGravimetry.

Magnetics

- Magnetic field feature for grid data and contours.

• Usually measured in mT
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousMagnetics.

GlobalElevation

- Merged bathymetric and topographic elevation data

• Though it is probably a good idea to keep Bathymetry and Topography seperate due to their differences, there are plenty of instances of merged data sets combining ocean depth with land height fields. This Feature supports those cases.
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousGlobalElevation.

OceanicAge

- Age of seafloor, for contours and grids.

• While oceanic age is most frequently represented with grids, it is still useful to pick out contours of specific ages.
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousOceanicAge.

CrustalThickness

- Crustal thickness data, typically represented using grids, related to Isopach data.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousCrustalThickness.

DynamicTopography

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• Seismic Tomography (MantleDensity) is used as a source of data to create DynamicTopography.
• An 'Instantaneous' copy of this class exists, InstantaneousDynamicTopography.

MantleDensity

- Density of the mantle, computed using Seismic Tomography.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• MantleDensity data can be applied to the creation of DynamicTopography grids.
• An 'Instantaneous' copy of this class exists, InstantaneousMantleDensity.

HeatFlow

- Oceanic heat-flow data

• Heat flow is typically measured by placing devices on the ocean floor to measure temperature. For example, heat will emanate from a MidOceanRidge.
• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousHeatFlow.

SedimentThickness

- Isopach data indicating sediment thickness using grids and/or contours.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• e.g. http://www.usawaterquality.org/conferences/2005/Posters/Negrini.pdf
• An 'Instantaneous' copy of this class exists, InstantaneousSedimentThickness.

Roughness

- Roughness data computed from Gravity grids.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• This feature is an example of one which would use gridded data almost exclusively, with little need for Contours and outlines. However, in any case of gridded data, there is the possibility that such contours may be desirable, and should be available as an option.
• An 'Instantaneous' copy of this class exists, InstantaneousRoughness.

SpreadingRate

- Sea-floor spreading rate.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousSpreadingRate.

SpreadingAsymmetry

- Asymmetry in sea-floor spreading rate.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousSpreadingAsymmetry.

Stress

- Stress grids and contour data.

• Currently, this feature provides for contour and outline data. This feature is intended to support gridded data in a future release.
• An 'Instantaneous' copy of this class exists, InstantaneousStress.

TectonicSection

- Superclass to group ridgelike and related tectonic features together.

• Plate-tectonic features that can form boundaries between plates fall under this class.
• An 'Instantaneous' copy of this class exists, InstantaneousTectonicSection.

• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] unclassifiedGeometry
  • All geometry defined for the feature where the purpose is not given or unclear.
• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] centerLineOf
  • The central line defining the tectonic feature, generally using gml:LineString, with the possibility of gml:MultiGeometry or gml:MultiCurve. This is the default location for imported geometry.
• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] outlineOf
  • Geometry specifying a closed or partial outline - expected to potentially use gml:MultiGeometry, gml:LineString and gml:Polygon. This may include Contours (or extents) associated with this tectonic section.
• contains gpml:plateId[0..1] leftPlate
  • Annotation property describing the plates on the "left" side of this tectonic section. Not to be used for reconstruction purposes, as these properties would be an imprecise representation of the crust on each side in many cases. Primarily of interest to the MidOceanRidge feature, where it is used for the purpose of a richer description.
  • Not a time-dependent property because, for MidOceanRidge at any rate, that's insanity. A MidOceanRidge -generates- crust. For other boundary features, like SubductionZone, this property is only really used as annotation, (i.e. "this SZ is mostly consuming plate 541") and doesn't need to be over-complex.
  • This property doesn't support multiple plateIds per side for similar reasons to the ones above; in the case of MidOceanRidge, the usefuless of this property hinges on the potential to e.g. interpolate between both sides of the MOR and determine velocity. If more than one plateId per side were supported, topology would have to be taken into consideration, and pieces would have to move at different rates - and so the MOR would have to be broken up into segments, PLATES style. Perhaps when we get segmented MORs in the next release GPGIM, we can consider these extra possibilities. Until then, there's really no point in making this more complex than it needs to be.
• contains gpml:plateId[0..1] rightPlate
  • Annotation property describing the plates on the "left" side of this tectonic section. Not to be used for reconstruction purposes, as these properties would be an imprecise representation of the crust on each side in many cases. Primarily of interest to the MidOceanRidge feature, where it is used for the purpose of a richer description.
  • Not a time-dependent property because, for MidOceanRidge at any rate, that's insanity. A MidOceanRidge -generates- crust. For other boundary features, like SubductionZone, this property is only really used as annotation, (i.e. "this SZ is mostly consuming plate 541") and doesn't need to be over-complex.
  • This property doesn't support multiple plateIds per side for similar reasons to the ones above; in the case of MidOceanRidge, the usefuless of this property hinges on the potential to e.g. interpolate between both sides of the MOR and determine velocity. If more than one plateId per side were supported, topology would have to be taken into consideration, and pieces would have to move at different rates - and so the MOR would have to be broken up into segments, PLATES style. Perhaps when we get segmented MORs in the next release GPGIM, we can consider these extra possibilities. Until then, there's really no point in making this more complex than it needs to be.

MidOceanRidge

Mid-Ocean Ridge - A spreading rift on oceanic crust

• The MidOceanRidge class needs to be pretty flexible. In the PLATES methodology, MOR lines are typically used to represent both the 'spreading' and 'transform' sections of the ridge - and so a lot of older data sets will have rigid MidOceanRidges once they are imported. Ideally, they would use an explicit Transform to join up MidOceanRidge and SubductionZone pieces.
• The other area that MidOceanRidge needs to encompass is those ridges that have become an "Extinct Ridge" through a process of ridge propagation. This is handled via the .isActive time-dependent property below.
• It is possible that later releases of the GPGIM will support a single MidOceanRidge Feature with heterogenous 'segments'.
• An 'Instantaneous' copy of this class exists, InstantaneousMidOceanRidge.

• contains TimeDependentPropertyValue<boolean>[0..1] isActive
  • 'true' while this MidOceanRidge is still active, 'false' if it has since become an "Extinct Ridge" due to ridge propagation in the area. Optional - if not present for a given time period, it is safe to assume the ridge is still actively generating crust.
  • Due to ridge jump / propagation, and various plate-tec forces in the region, a midoceanridge-transformfault-midoceanridge area may start ignoring the extra midoceanridge and transform, and instead start 'propagating' one ridge to take over the job of the other.
  • An "Extinct Ridge" is a MidOceanRidge that has 'died' by this process, and no longer creates oceanic crust.
  • #Time-Dependency: This property can be time-dependent - in most data, it would likely be a simple ConstantValue<boolean>, but if the user wishes to model the activity over time, the data could use PiecewiseAggregation<boolean>, supporting separate TimeWindows to describe the active period and inactive period of this MidOceanRidge.

ContinentalRift

Continental Rift - A spreading rift on continental crust

• Functionally, this behaves similarly to MidOceanRidge, but a ContinentalRift is defined for continental crust only.
• An 'Instantaneous' copy of this class exists, InstantaneousContinentalRift.

SubductionZone

- A zone of descending lithospheric plate

• The standard model of a subduction zone is a linear tectonic region which consumes plate material on one side, while being largely 'attached' to a plate on the other side. Similarly to MidOceanRidge, the leftPlate and rightPlate properties are often set to advise approximately which plate is being consumed. The SubductionZone is always 'attached' to the overriding plate, as far as the gpml:plateIds are concerned.
• Not necessarily a 'Zone', could be a linelike feature or have an additional polygon geometry.. The gml property .centerLineOf is used to indicate where the subducting plate meets the overriding plate.
• An 'Instantaneous' copy of this class exists, InstantaneousSubductionZone.

• contains enumeration TimeDependentPropertyValue<SubductionSideEnumeration>[0..1] subductingSlab
  • Indicates the side of the line that the subducting slab is on. The overriding slab will be on the opposite side.
  • .subductingSlab is an enumeration: Assuming there is a suitable centerLineOf supplied, and understanding that the order of points in the line matters, we can establish a "left" side and a "right" side to the .centerLineOf. this property indicates which of those "left" and "right" sides the subducting slab is on. The overriding plate will be on the opposite side.
  • = "Left" : The subducting slab is on the left of this SubductionZone, according to the directed gml:LineString .centerLineOf
  • = "Right" : The subducting slab is on the right of this SubductionZone, according to the directed gml:LineString .centerLineOf
  • = "Unknown" : the value of this property is officially unknown; there is no information about which side of the SubductionZone is which.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which side the subducting slab is on. The property is unspecified or indeterminate.
  • #Time-Dependency: Most common use-case would be a ConstantValue<enumeration>, but there is the --possibility-- that a single SubductionZone may change polarity, and that someone may want to model that in GPML, in which case the data would be a PiecewiseAggregation<enumeration>
• contains FeatureReference<IslandArc>[0..*] islandArc
  • Since there could be multiple small island arcs that are part of a large subduction zone, we will let the subduction zone keep track of its associated IslandArc(s), if any.

OrogenicBelt

- A linear or arcuate zone on a regional scale which has undergone compressional tectonics

• The standard model of an orogenic belt is a linear tectonic region in a mountainous region where two plates have collided. Similar to a subduction zone, one plate has often overridden the other, so we use a similar model to that of gpml:SubductionZone. As with MidOceanRidge, the leftPlate and rightPlate properties are set to advise approximately which plate is overriding which.
• While certainly OrogenicBelt can be treated similarly to SubductionZone, as there was presumably a SubductionZone that pulled the OrogenicBelt into existence (eg India & Asia), there exists potential for there to be no clearly defined overriding & overridden plate. Similar to SubductionZone, we have a .subductingSlab property which is optional.
• An 'Instantaneous' copy of this class exists, InstantaneousOrogenicBelt.

• contains enumeration TimeDependentPropertyValue<SubductionSideEnumeration>[0..1] subductingSlab
  • Indicates the side of the line that the subducting slab is on (if applicable). The overriding slab will be on the opposite side.
  • .subductingSlab is an enumeration: Assuming there is a suitable centerLineOf supplied, and understanding that the order of points in the line matters, we can establish a "left" side and a "right" side to the .centerLineOf. this property indicates which of those "left" and "right" sides the subducting slab is on. The overriding plate will be on the opposite side.
  • = "Left" : The subducting slab is on the left of this OrogenicBelt, according to the directed gml:LineString .centerLineOf
  • = "Right" : The subducting slab is on the right of this OrogenicBelt, according to the directed gml:LineString .centerLineOf
  • = "Unknown" : the value of this property is officially unknown; there is no information about which side of the OrogenicBelt is which.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which side the subducting slab is on. The property is unspecified or indeterminate.
  • #Time-Dependency: Most common use-case would be a ConstantValue<enumeration>, but there is the --possibility-- that a single SubductionZone (or OrogenicBelt in this case) may change polarity, and that someone may want to model that in GPML, in which case the data would be a PiecewiseAggregation<enumeration>

Transform

- Regional scale strike-slip plate bounary

• Used to link MidOceanRidge s and SubductionZone s together to form a closed plate boundary.
• This may not see as much use as MidOceanRidge; the current methodology employed in PLATES data files typically ignores Transforms altogether, and uses 'MOR' lines for both the spreading ridge and the transform 'kink's. In addition, the parts of simple PLATES-style Isochron lines that are perpendicular to the ridge can also be considered 'transforms' or 'fracture zones', because they indicate the paleo-offset between two ridge sections.
• An 'Instantaneous' copy of this class exists, InstantaneousTransform.

• contains enumeration TimeDependentPropertyValue<StrikeSlipEnumeration>[0..1] motion
  • .motion is an enumeration: types are:
  • = "LeftLateral" : also called Sinistral motion. When viewed from one side of the Transform boundary, the opposite side appears to be moving to the observer's left.
  • = "RightLateral" : also called Dextral motion. When viewed from one side of the Transform boundary, the opposite side appears to be moving to the observer's right.
  • = "Unknown" : the value of this property is officially unknown; there is no information about the transform's motion.
  • = "None" : There is no motion along the this Transform. Unlikely in this case but included for consistency with Fault.strikeSlip
  • <not present> : This property is optional. If not present, it indicates that there is no information about the motion of this Transform boundary. The property is unspecified or indeterminate.
  • #Time-Dependency: Most common use-case would be a ConstantValue<enumeration>, but there are surely instances of Transforms' motion changing direction, and that means someone may want to model that in GPML, in which case the data would be a PiecewiseAggregation<enumeration>

FractureZone

- Inactive fracture in the crust that was once part of a Transform boundary.

• In PLATES, small fracture-zone lines are used in a segmented fashion- each segment of the line has an appropriate time of appearance and time of disappearance, to simulate the growth of the fracture zone.
• For GPlates and GPML, a more ideal solution would treat the entire FractureZone as one complete gml:Feature, with its geometry being time-dependent (possibly using locus geometry). For the present, it is better to follow the older PLATES method, since that is how much of the data is structured and it would require a human to reconstitute the segments.
• gpml:FractureZone has an advantage over the old PLATES format; all gpml:ReconstructableFeatures have an optional property called .truncatedSection, which allows for one or more FractureZone pieces to be semantically linked.
• Interestingly, a FractureZone's geometry is a SmallCircleArc, roughly indicating the rotation pole when the Transform that created it was active.
• An 'Instantaneous' copy of this class exists, InstantaneousFractureZone.

PassiveContinentalBoundary

- Border line between oceanic and continental crust

• A quite simple, linelike boundary indicating the change between continental and oceanic crust. Since this change is broad and hard to pin down, we expect two main types of continental boundary, an "Inner" ContinentalBoundary and "Outer" ContinentalBoundary. Naturally, which of these labels gets used to describe a gpml:PassiveContinentalBoundary depends largely on the source of the data, who digitized the line, and whether that aspect of the data was recorded in the original source.
• Does not have to be closed, can be a simple line segment. For closed polygons, you want InstantaneousClosedContinentalBoundary and ClosedContinentalBoundary.
• An 'Instantaneous' copy of this class exists, InstantaneousPassiveContinentalBoundary.

• contains enumeration ContinentalBoundaryEdgeEnumeration[0..1] edge
  • .edge is an enumeration:
  • = "InnerContinentalBoundary" : This PassiveContinentalBoundary defines the Inner edge of the continental boundary (closest to centre of continental crust)
  • = "OuterContinentalBoundary" : This PassiveContinentalBoundary defines the Outer edge of the continental boundary (furthest away from centre of continental crust, closest to oceanic crust)
  • = "Unknown" : This PassiveContinentalBoundary was digitised or imported without any data telling us how the boundary was chosen with regard to inner and outer edges of the continental crust. The value of this property is officially unknown.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which edge of the boundary is represented by this line. The property is unspecified or indeterminate.
• contains enumeration ContinentalBoundarySideEnumeration[0..1] continentalSide
  • .continentalSide is an enumeration: Assuming there is a suitable centerLineOf supplied, and understanding that the order of points in the line matters, we can establish a "Left" side and a "Right" side to the .centerLineOf. this property indicates which direction leads to the continental crust.
  • = "Left" : The continental crust for this PassiveContinentalBoundary can be found to the left, oceanic crust can be found on the right. Depending on the .edge of this PassiveContinentalBoundary, this may also imply some transitional "grey area" crust is on one side or the other.
  • = "Right" : The continental crust for this PassiveContinentalBoundary can be found to the right, oceanic crust can be found on the left. Depending on the .edge of this PassiveContinentalBoundary, this may also imply some transitional "grey area" crust is on one side or the other.
  • = "Unknown" : No information is known about which {continental,oceanic} side is which for this PassiveContinentalBoundary. This property is officially unknown.
  • <not present> : This property is optional. If not present, it indicates that there is no information about which side of the boundary is continental crust and which side is oceanic. The property is unspecified or indeterminate.

Isochron

- Simple line defining points of equal age for oceanic crust

• For the GPGIM1.5, we just want a simple, rigid Isochron replacement for the PLATES model. It includes Paleo-Ridge and Paleo-Transform sections.
• A common property associated with an Isochron is its "age". It defines the point in time that this Isochron is believed to originate at, in Ma. However, we already have a .validTime property inherited from TimeVariantFeature, so to work out the 'age' of the Isochron, one can look at .validTime(a TimePeriod).begin(a TimeInstant)
• An 'Instantaneous' copy of this class exists, InstantaneousIsochron.

• contains FeatureReference<Isochron>[0..*] conjugate
  • A reference to the 'pair' or 'twin' of this isochron. Due to Isochrons getting split into pieces in PLATES data, it must support more than one conjugate on the other side of the MOR.
• contains gpml:plateId[0..*] conjugatePlateId
  • A reference to the plate Id (general-purpose plate Id or specific plate Id for motion of a cluster of Features) that has the 'pair' or 'twin' of this isochron. Due to Isochrons getting split into pieces in PLATES data, it must support more than one conjugate on the other side of the MOR. This property is intended to support transition from PLATES style information to the feature-centric GPlates model.
• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] unclassifiedGeometry
  • All geometry defined for the feature where the purpose is not given or unclear.
• contains TimeDependentPropertyValue<gml:_Geometry>[0..1] centerLineOf
  • The central line defining the Isochron, using gml:LineString for the digitization, with the possibility of gml:MultiGeometry or gml:MultiCurve. This is the default location for imported geometry.

MagneticAnomalyIdentification

- Magnetic 'pick' to identify age of oceanic crust based on magnetostratigraphic time-scale.

• The 'pick' is taken from the magnetic anomaly reading and the ship path.
• An 'Instantaneous' copy of this class exists, InstantaneousMagneticAnomalyIdentification.

• contains gml:Point[1] position
  • lat/long point indicating the physical location of the pick.
  • not time dependent because it is just a point, points don't deform.
• contains string[0..1] polarityChronId
  • text code indicating which Polarity Chron this pick is linked to: other picks on different ship-tracks will share this Id if they belong to the same Chron. e.g. "C34"
  • note that we want this to be unique for each Chron, so the tradition of packing extra info like the 'young/old' value onto the end of the Id ("C34o0.2") is discouraged; polarityChronOffset can be used to store the young/old offset, and any miscellaneous extra information can go in metadata, gml:name, gml:description, or gpml:subcategory as appropriate.
  • it is called "polarity chron" because it is the 'chron' of all positions sharing the same polarity.
• contains double[0..1] polarityChronOffset
  • A number from 0.0 to 1.0, indicating the proportion from 'young' to 'old'; 0.0 = young, 1.0 = old; This property stores the offset of this pick's chron position compared to the synthetic chron.
• contains FeatureReference<MagneticAnomalyShipTrack>[0..1] shipTrack
  • Optional reference to the MagneticAnomalyShipTrack that this pick originates from.

MagneticAnomalyShipTrack

- Ship Track data for Magnetic 'pick's

• For now, this allows us to define the map-view path taken by a particular ship for magnetic anomaly data. You can give it a 'ship track Id' if you want, via gml:name. The MagneticAnomalyIdentification s or 'picks' have a reference to this Feature to indicate the particular ship track that the pick originated from.
• in future releases, this Feature may also be used to contain the magnetic "wiggle" recorded along the ship track.
• An 'Instantaneous' copy of this class exists, InstantaneousMagneticAnomalyShipTrack.

• contains gml:_Geometry[0..1] unclassifiedGeometry
  • All geometry defined for the feature where the purpose is not given or unclear.
• contains gml:_Geometry[0..1] centerLineOf
  • The central line defining the path the ship took, generally using gml:LineString, with the possibility of gml:MultiGeometry or gml:MultiCurve. This is the default location for imported geometry.
• contains FeatureReference<MagneticAnomalyIdentification>[0..*] pick
  • An (optional) reference to the MagneticAnomalyIdentification s recorded from this ship track data. A reference because these data sometimes exist independently of each other, so they should both be gpml:Features, Optional because you may get a bunch of picks all in close proximity and things stop being clear, odd datasets, etc.

FractureZoneIdentification

- Pick to identify fracture zone.

• The 'pick' can be taken from a magnetic anomaly reading and a ship track - or it can be taken from some other gridded data source, or chosen without any justification at all.
• These picks are useful to create Isochrons and align them.
• As a FractureZoneIdentification can be picked from a wide variety of sources, it is recommended to use the standard gpml:subcategory property if you want to indicate where this pick comes from.
• Suggested Subcategories:
• = "Bathymetry" : chosen based on a Bathymetry grid.
• = "Topography" : chosen based on a Topography grid.
• = "Gravity" : chosen based on a Gravity grid.
• = "Magnetic" : chosen based on a Magnetic grid.
• An 'Instantaneous' copy of this class exists, InstantaneousFractureZoneIdentification.

• contains gml:Point[1] position
  • lat/long point indicating the physical location of the pick.
  • not time dependent because it is just a point, points don't deform.
• contains string[0..1] polarityChronId
  • text code indicating which Polarity Chron this pick is linked to: other picks on different ship-tracks will share this Id if they belong to the same Chron. e.g. "C34"
  • it is called "polarity chron" because it is the 'chron' of all positions sharing the same polarity.
  • We want this to be unique for each Chron, so packing extra info like the 'young/old' value onto the end of the Id ("C34o0.2") is discouraged; polarityChronOffset can be used to store the young/old offset, and any miscellaneous extra information can go in metadata, gml:name, gml:description, or gpml:subcategory as appropriate.
• contains double[0..1] polarityChronOffset
  • A number from 0.0 to 1.0, indicating the proportion from 'young' to 'old'; 0.0 = young, 1.0 = old; This property stores the offset of this pick's chron position compared to the synthetic chron.
• contains FeatureReference<MagneticAnomalyShipTrack>[0..1] shipTrack
  • Optional reference to the MagneticAnomalyShipTrack that this pick originates from.

AbstractGeologicalPlane

- Abstract base for all Geological Surface Planes, including Surfaces such as Bedding Surfaces, Cleavage, intangible planes such as Fold Plane, as well as Contacts and Faults.

• an AbstractGeologicalPlane by itself will not be instantiated; You want a subcategory of GeologicalPlane(BeddingPlane, CleavagePlane), or perhaps a FoldPlane, or one of the various specialisations of GeologicalContact.
• An 'Instantaneous' copy of this class exists, InstantaneousAbstractGeologicalPlane.

• contains gml:_Geometry[0..1] unclassifiedGeometry
  • All geometry defined for the feature where the purpose is not given or unclear.
• contains gml:_Geometry[0..1] centerLineOf
  • The central line defining the tectonic feature, generally using gml:LineString, with the possibility of gml:MultiGeometry or gml:MultiCurve. This is the default location for imported geometry.
  • As with many LineStrings in GPML, the ideal situation would enforce a single line where the order of points is kept constant, in order to establish that the line is directed and create a situation where we can describe the "left" and "right" sides of the line. But the ideal situation may not always be available, especially with data imported from other sources.
  • Naturally, this is the map-view or 'strike' of the surface or plane for GPlates to use, not a cross-section. Cross-sections may come later.
• contains enumeration DipSideEnumeration[0..1] dipSide
  • The side of the line that the 'dip' is on, giving a hint at what the plane of the surface looks like.
  • = "Left" : The Plane (e.g. Fault) dips to the 'Left' of this line (relative to the order of points defining the Strike)
  • = "Right" : The Plane (e.g. Fault) dips to the 'Right' of this line (relative to the order of points defining the Strike)
  • = "Undefined" : If the Dip angle of the Plane is 90 degrees (straight down), this property is not clearly defined regardless of its value. For new data, it may be convenient to assign it this "Undefined" value, but bear in mind that when .dipAngle == 90, any value the .dipSide property takes should be considered arbitrary.
  • = "Unknown" : the value of this property is officially unknown; there is no information about the dip of the GeologicalPlane (for example, the plane of a Fault's surface.).
  • <not present> : This property is optional. If not present, it indicates that there is no information about dip of this Plane. The property is unspecified or indeterminate.
  • Important note: it is unlikely, but possible, for the 'dipAngle' of a Fault(or any other Plane) to be 90 degrees, in other words, straight down. In this case, the 'dipSide' is not clearly defined, and any value this property takes should be considered arbitrary. The value "Undefined" can be used if desired, but bear in mind that data imported from other sources may come with a specific direction which is nevertheless irrelevant.
• contains gpml:angle[0..1] dipAngle
  • The angle of the 'Dip' of the Plane (BeddingSurface, Unconformity, Fault etc). It is the acute angle measured from the horizontal at the top of the Dip.
  • <not present> : This property is optional. If not present, it indicates that there is no information about the dip of this GeologicalPlane available. The property is unspecified or indeterminate.