From Validation to Database Management

CityGML Experience: From Validation to Database Management Kean  Huat  SOON,  Eric  LOW,  Zhen  Hao  NG  and  Victor  KHOO

Outline • Background: WOG 3D National Topographic Mapping Project

• CityGML • Validation Process • Management of CityGML Data in DBMS • Outlook (Conclusions)

WOG 3D National Topographic Mapping Project

Background CityGML Validations Data  Management Conclusions

• Two Phases: Phase 1 – Airborne; Phase 2 – Mobile, for the whole Singapore

• @Phase 1: Modeling for Relief, Waterbody, Vegetation, Bridge and Building (LOD0-LOD2)

• @Phase 2: City Furniture, Relief, Tunnel and Transportation (LOD0-LOD2)

• To develop a national 3D topographic database, which is based on CityGML 2.0 schema

CityGML

Background CityGML Validations Data  Management Conclusions

• Open Geospatial Consortium (OGC) encoding standard since 2008 • developed by international experts

• Open standard • • • •

XML-based not confined by proprietary software, i.e. neutral machine readable and processable can be opened in any Operation Systems (MacOS, Windows, Linux,etc)

CityGML 2.0 Thematic Modules Application  Domain  Extensions  (ADE) Generics

CityGML  Core  /  GML  3.1.1 (Source:  Claus  Nagel)

WaterBody

Vegetation

Tunnel

Transportation

Relief

LandUse

CityObjectGroup

CityFurniture

Bridge

Building

Appearance

Background CityGML Validations Data  Management Conclusions

LOD 0 to LOD 4

Background CityGML Validations Data  Management Conclusions

LOD  0  –  only   FootPrint  and/or   RoofEdge

LOD  1  –  Block   model  w/o  roof   structures

6

LOD  2  –   Differentiated   roof  structures,   building   installations

LOD  3  –  Detailed   architecture   model

LOD  4  –  LOD  3  +   model  of  the   interior  space (Source:  OGC)

(Source:  TUDelft)

Background CityGML Validations Data  Management Conclusions

CityGML Building Model

CityObject

Abstract  Building Building

roof  surface

Building  Part

Boundary  Surface

Roof  Surface

Wall  Surface

wall  surface

ground  surface

3D  Geometry  +  Topology

+    Semantics    +  

Appearance

Background CityGML Validations Data  Management Conclusions

CityGML Building Model

CityObject

Abstract  Building Building

roof  surface

Building  Part

Boundary  Surface

Roof  Surface

Wall  Surface

wall  surface

ground  surface

3D  Geometry  +  Topology +    Semantics    +   Appearance

CityGML as DB Schema

Background CityGML Validations Data  Management Conclusions

CityGML as Exchange Format

Background CityGML Validations Data  Management Conclusions

Singapore Building LOD 2 Singapore’s  Spatial  Reference  System  in  3D A  unique  GML  ID  for  3D  Buildings Singapore  Localized  Codelists

Address

Background CityGML Validations Data  Management Conclusions

Background CityGML Validations Data  Management Conclusions

Spatio-Semantic Coherence

critical for complex queries, analysis and simulations “Geometry  objects  know  WHAT  they  are” CityObject

Abstract  Building Building

Building  Part

Boundary  Surface

Roof  Surface

“Semantic  objects  know  WHERE  they  are  and  their   spatial  extent”

11

Wall  Surface

Applications • • • • • • • • •

Development  Planning Rainwater  Runoff  Assessment Green  Applications Flood  modeling Building  Height  Study Solar  Potential  Study Telecommunication  Coverage Climate  Change  Study Pollution  Dispersion,  etc. 12

Background CityGML Validations Data  Management Conclusions

(Source:  CyberCity3D)

Validations

Background CityGML Validations Data  Management Conclusions

Analysis  and  simulation  results  are  not  reliable  if  the  quality  of  the   models  is  not  ensured. Validations  have  been  carried  out  to  check • schema  (e.g.  compliance  and  external  reference) • themes  (e.g.  Building,  Bridge) • geometries  (polygon  and  solid) • semantics  (e.g.  wall  surface,  roof  surface) • database  import  (e.g.  data  type) Using  validation  tools • FZK  Viewer • 3D  CityDB  Importer/Exporter  v3.0 13 • CityDoctor

Background CityGML Validations Data  Management Conclusions

Validation Process Models validate

accept Validation  Tools

Quality  Checks   (SLA) reject

produce

communicate Modelers   (Vendors) 14

Discussions/Requirements   (SLA  and  vendors)

3D  Topography  DB   (SLA)

Background CityGML Validations Data  Management Conclusions

Validation Process Models validate

accept Validation  Tools

Quality  Checks   (SLA) reject

produce

communicate Modelers   (Vendors) 14

Discussions/Requirements   (SLA  and  vendors)

3D  Topography  DB   (SLA)

Background CityGML Validations Data  Management Conclusions

FZK Viewer

• Visual and manual • attribute checks include gml id, codelists, etc.

e.g.  address,  external  reference,  measuredHeight roof  type

e.g.  volume,  surface  area

15

Building?

3D CityDB Importer/Exporter 3.0

Background CityGML Validations Data  Management Conclusions

• Fully automated • Schema checks for all

thematic modules (e.g. Building, Relief, Bridge)

• Database import check • Includes other

functionalities e.g. import and export from database

http://www.3dcitydb.net/  

CityDoctor Validation Tool

Color  Preference

Content  in   tree  structure Four  different  views

Geometric   Table Validation  Results  Panel

http://citydoctor.hft-­‐stuttgart.de

Background CityGML Validations Data  Management Conclusions

Validation   Results  in  XML

Validation  Criteria

CityDoctor Validations Polygon  Checks

Solid  Checks

Background CityGML Validations Data  Management Conclusions

• Building models are

validated automatically through Polygon Checks, Solid Checks, and Semantic Checks.

Semantic  Checks

• Currently the tool is Additional  Checks

18

limited to Building only

Background CityGML Validations Data  Management Conclusions

Polygon Checks 1.  “A  linear  ring  must  consist  of  a  minimum  of  4  points”     2.  “First  and  last  point  of  a  linear  ring  are  identical.  “  

X

X

3.  “All  points  of  a  linear  ring  are  different,  with  exception   of  first  and  last  point.  “   4.  “ Two  edges  can  intersect  only  in  one  start-­‐/end  point.   Other  points  of  intersection  or  touching  are  not  allowed   (to  account  for  rounding  errors  or  polygons  which  are  not   perfectly  planar,  a  small  tolerance  is  allowed).  “   5.  “All  points  of  the  polygon  must  be  located  in  a  plane  (a   small  tolerance  is  allowed).  “

X X X

19

(Source:  Alam  et.  al  2013)

X

Solid Checks

Background CityGML Validations Data  Management Conclusions

1.“The  minimum  number  of  polygons  to  define  a  solid  is  four.  They   must  be  situated  in  different  planes.”     2.“A  valid  intersection  of  two  polygons  of  a  solid  either  contains  a   common  edge,  a  common  point  of  a  linear  ring,  or  is  empty.   Common  edges  and  points  must  be  elements  of  both  polygons.  ”   X

3.“Each  edge  of  a  linear  ring  defining  a  polygon  is  used  by  exactly   one  neighboring  polygon.”    

X

4.“Consistent  orientation  of  polygons  of  a  solid  such  that  common   edges  according  to  check  4  are  used  in  opposite  direction.  ”   X

5.“The  normal  vectors  of  the  polygons  must  point  towards  the   outside  of  the  solid.  ”     6.“All  parts  of  a  solid  must  be  connected.  ”

(Source:  Alam  et.  al  2013)

20

√

X

Semantic Checks 1. “Orientation  of  RoofSurface,  WallSurface  and   GroundSurface  elements”   2. “measuredHeight  in  same  range  as  height  of   building  geometry”   3. “numberOfStoreysAboveGround  plausible  for   height  of  the  building  geometry”   4. “numberOfStoreysBelowGround  plausible  for  height   of  underground  geometry  of  the  building”     5. “Relationship  of  Building  and  BuilidingPart”  

(Source:  Alam  et.  al  2013)

21

Background CityGML Validations Data  Management Conclusions

Background CityGML Validations Data  Management Conclusions

Loading Content to DBMS CityGML  Files All  faces  of  building

Roof

Wall

Wall

SURFACE_GEOMETRY

                                           …….            …..  

Wall

Building

Database

                                 ….                        

Wall

                                           …….            …..