GIS Modeling N.L. Sarda IIT Bombay For class-room usage only (based on ISO standards documents)

Whoville Cedar Lake Integrated View Internet Display multiple layers of geographic data within a single application Display multiple layers of geographic data within a single application Query and update Query and update Discover, access and retrieve views from multiple servers Discover, access and retrieve views from multiple servers Crime Social Services Land Parcel Weather Environment Parcels Roads Images Boundaries... Catalog View Standards for modeling Geographic data – multiple sources GML from OGC

Need for standards For sharing For inter-operability For data exchange Heterogeneity exists at –Conceptual/modeling/User-view levels –At representation level –At storage level ISO/OGC provides a framework addressing all these levels –Separate description from data (schema and instances)

Data interchange - using application schema

From real-world to data - based on geographic features

Create application model

GML Application Schemas GML Schemas Cadastre, Land Use Cadastre, Land Use Traffic And Transport Traffic And Transport Telecom Environ- ment Environ- ment … … XML Technologies / W3C

ISO framework Provide concepts for defining features at conceptual level Core concepts : –Feature –Properties : attributes, operations and relationships –supports spatial and non-spatial properties of objects Advanced concepts : metadata, geography, collections, … leaves it to implementers to decide whether application schemas and datasets are stored in native GML or whether GML is used only for schema and data transport

GML Schemas GML Schemas are horizontal and not focused on a specific application domain They provide common constructs and concepts which may be used by all the different application domains

GML Schemas Base schemas, general syntax, feature model, metadata mechanisms Basic geometry (0d, 1d, 2d) Additional geometric primitives (0d, 1d, 2d, 3d) Geometric composites Geometric aggregates Coordinate reference systems Topology Temporal information and dynamic features Definitions and dictionaries Units, measures and values Directions Observations Coverages Default styling

GML Application Schema Schema to describe features, coordinate reference systems, geometry, topology, time, units of measure and generalized values. An application schema declares the actual feature types and property types of interest for a particular domain. These involve defining application-specific types which are derived from types in the standard GML schemas, or by directly including elements and types from the standard GML schemas.

Modeling Based on defining features Feature is a type or class with properties that define –Its attributes –Its operations –Its relationships with other features

Basic UML components

General Feature Model

Feature Attributes

Modelling Feature Types Road name class maintainer I95 Interstate xyz centerLine gml:Curve reach consensus about the vocabulary --- feature types and their properties

Feature in GML I95 Interstate... xyz

Relationships between features

Application schemas Uses base schemas May also use other application schemas –As domains are inter-related –Road network may be used in Transportation, Tourism, … Basic schemas also categorized –Temporal –Quality …

Using base schemas in application schema

Example schema integration

From feature catalogue to schema

UML Modeling of Application Schema the data provider and the data receiver are supposed to agree on a so-called application schema. An application schema is typically UML class diagrams expressing the structure and content of the data to be exchanged. The standard ISO Rules for application schema prescribes how to make an application schema in UML.

UML Application Schema (Example) Region dateCreated: date population: integer extentOf: polygonPropertyType River riverName: String remark: String centerLineOf: LineStringPropertyType Roads roadName: String classification: String linearGeometry: LineStringPropertyType City cityName: String remark: String pointProperty: pointPropertyType AbstractFeature AbstrctFeatureCollection

Example

Top10vector

Spatial Objects Infrastructure Type Accessibility Status Cultivation Type Cultivation Position Height Class Height Status Height Level Name Grounds Use Physical Appearance Accessibiltty Appearance Height Level Name * ** Top10Object (is a collection) Top10Schema

Top10Object TemporalObject BeginDate EndDate MetadataObject SourceType SourceDescription Exactness Topic (time and metadata is associated with features and not with collections)

Infrastructure Rail Road Part Traffic Use Physical Appearance Track Width No. Travel by Train Position Track Electrification Height Level GeometryProperty Water Part Water Type Salt Content Physical Appearance Use Stream Direction Height Level Name UseEnumeration Water Purification Swimming Pool Remaining StreamDirectionEnumeration One Direction Two Direction Way Divide Way Type HeadTraffic Use Crossings No. of Lanes Street Name Way No. Hardening Width Hardening Type Hardening Material Hardening with Class HardeningwithClassEnum >7 m 4-7 m 2-4 m <2 m ElectrificationEnumeration Electrified Not Electrified

ferry NH1 4 lanes NH1 - B NH1 - A NH1 Over Bridge Express Highway Administrative Boundary House 1 House 2 NH1 River Ganges A Real World Example (identify objects and their types as per Top10 schema)

Ferry( O 7 ) NH1 4 lanes NH1 - B NH1 - A NH1 Over Bridge(O 10 ) Express Highway Administrative Boundary House 1 House 2 NH1 River Ganges( O 8 ) O1O1 O 1 = Object 1 O2O2 O3O3 O4O4 O5O5 O6O6 O9O9 O 12 O 13 O 14 O 15 Road below the Bridge(O 11 ) N All objects given unique IDs

:AdministrativeAreas Type=“Administrative Boundary” Name=”Political” gml: GeometricProperty Fid=“TOP ” gml: lineString , , , , , , , , , …. Maharastra:Top10ThemasMumbai:Top10Thema :Spatial Objects (O 1 ) Object Diagram of the above Real World Example

:Spatial Objects Road: WayPart beginDate = “6 jul 2004” No. of Lanes = “2” Street Name = “NH1” Way No.= “W7488” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Road” beginDate inherited from TemporalObject gml: Polygon , , , , Road: WayPart gml: Polygon , , , , beginDate = “6 jul 2004” No. of Lanes = “4” Street Name = “NH1” Way No.= “W7488” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Road” Road: WayPart gml: Polygon , , , , , beginDate = “6 jul 2004” No. of Lanes = “2” Street Name = “NH1” Way No.= “W7488” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Road” (O 2 ) (O 3 ) (O 4 )

:Spatial Objects Road: WayPart gml: Polygon , , , , …. beginDate = “6 jul 2004” No. of Lanes = “2” Street Name = “NH1” Way No.= “W7488” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Road” Road: WayPart gml: linearRing , , , , ….. beginDate = “6 jul 2004” No. of Lanes = “1” Street Name = “NH1” Way No.= “W7488” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Road” Crossing: WayPart gml: Polygon , , , , …. beginDate = “6 jul 2004” No. of Lanes = “2” Street Name = “NH1” Way No.= “W7488” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Ferry” gml: Polygon , , , , …. (O 5 ) (O 6 ) (O 7 ) (O 8 ) :Water Part Water Type=“River” Salt Content=“Nil” Use=“Remaining” Direction=“OneDirection” Height Level=“0” Name=“Ganges” gml: GeometricProperty Fid=“TOP ” :Infrastructure

:Spatial Objects Road: WayPart beginDate = “6 jul 2004” No. of Lanes = “2” Street Name = “NH1” Way No.= “W7488” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Road” gml: Polygon , , , , Road: WayPart gml: Polygon , , , , beginDate = “6 jul 2004” No. of Lanes = “4” Street Name = “NH1” Way No.= “W7488” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Road” (O 9 ) (O 10 ) Road: WayPart gml: lineString , …. beginDate = “6 jul 2004” No. of Lanes = “2” Street Name = “NH1” Way No.= “W7488” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Road” (O 11 ) Overbridge Road under bridge Road_under_bridge and Overbridge represents the same area.

:Spatial Objects Road: WayPart gml: Polygon , , , , …. beginDate = “6 jul 2004” No. of Lanes = “1” Street Name = “NH1-A” Way No.= “W7488” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Road” Crossing: WayPart gml: Polygon , , , , …. beginDate = “6 jul 2004” No. of Lanes = “1” Street Name = “NH1-B” Way No.= “W7488-B” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Road” Road: WayPart gml: Polygon , , , , …. beginDate = “6 jul 2004” No. of Lanes = “2” Street Name = “NH1” Way No.= “W7488” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Road” (O 12 ) (O 13 )(O 14 ) Road: WayPart gml: Polygon beginDate = “6 jul 2004” No. of Lanes = “2” Street Name = “NH1” Way No.= “W7488” Height Level= “0” gml: GeometricProperty Fid=“TOP ” Type=“Road” (O 15 ) , , , , ….

An Example of a Temporal Feature Ferry(O7) cannot be used on Summer Season as river(O8) may be dry. So NH1 will be closed for those two months. ferry NH1 - B NH1 - A Over Bridge Express Highway Vehicles from East has to choose Express Highway instead. E O7O7 River ( O 8 )

UML-to-GML Encoding The mapping UML Application Schema to the corresponding GML Application Schema is based on a set of encoding rules. These encoding rules are compliant with the rules for GML Application Schemas The schema encoding rules are based on the general idea that the class definitions in the application schema are mapped to type and element declarations in XML Schema.

UML-to-GML Encoding

Geometric primitives

Geometric composites

Topology Describes ‘invariant’ structural relationships (preserved thru deformations, twisting, etc) Building blocks are Nodes, Edge, Face, … Represent geometric primitives Point, Curve, Surface, … To study reachability, paths, …

Topology Model The topology model of the road network encodes Intersections as Nodes Road segments as edges and Collective relationships between edges and nodes Topology Edge Node Curve Point Property Curve Property

ferry NH1 4 lanes NH1 - B NH1 - A NH1 Over Bridge Express Highway NH1 River Ganges Topology Model of NH1 Road Network n1 n2 n3 n4 n1 = Node 1 e1 = Edge 1 e1 e2 e3 e4

We can represent the Nodes in two ways. - as Objects Here the objects itself can be assigned as nodes. - as Geometry (preferred by OGC) Here the co-ordinates can be considered. But the problem is even a small mismatch in the co-ordinates result in the unidentification of that node.

n1(10,20)n3(30,20) n4(40,30) e1e2 e4 n2(20,25) e3 10,20 ……. 10,20,20,25 ……. n1 is the object O 2 n2 is the object O 5 (NH1 Circle) n3 is the object O 10 (Bridge) or O 11 (Road) Nodes as Objects

But the problem is which Object we can assign to node n3? (O10) or (O11) Different features can share, partly or completely, the same geometry when they appear to occupy the same position. To share a common geometry, spatial feature attributes must share one or more Geometric Objects. Nodes as Geometry

Bridge Type Name Road Name No. of Lanes gml:Curve geometry (O 10 )(O 11 ) This schema requires every Bridge to share the geometry of a Road, but a Road may not have to share the geometry of a Bridge. Nodes as Geometry

Spatial complexes – an example

GML 3.0 Temporal Define elements for describing the temporal characteristics of geographic data The underlying spatiotemporal model permits –feature-level and attribute-level time stamping –basic support for tracking moving objects –basic support for dynamic features

GML 3.0 Temporal

Using temporal schema for building history

Summary Need to define vocabulary (ontology) Define basic themes, feature catalogues Sharing by publishing application schemas Share data in GML format Modeling for NSDI requires coordination and collaboration