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Provision of interoperable datasets to open GI to EU communities

Magistrato alle Acque di Venezia. Provision of interoperable datasets to open GI to EU communities. Thematic Working Group Elevation “Towards Seamless Terrains”. Project funded by eContent plus P rogramme. Towards Seamless Terrains. 1 – Generalities 2 – Terrain modeling

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Provision of interoperable datasets to open GI to EU communities

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  1. Magistrato alle Acque di Venezia Provision of interoperable datasets to open GI to EU communities Thematic Working Group Elevation “Towards Seamless Terrains” Project funded by eContentplus Programme

  2. Towards Seamless Terrains • 1 – Generalities • 2 – Terrain modeling • 3 – Various fragmentations • 4 – Coordinate transformation • 5 – Cross-border aggregation • Same models • Different models • 6 – Final remarks Project funded by eContentplus Programme

  3. 1 – Generalities http://www.gug.bv.tum.de/seiten-e/technik/physik.htm l Project funded by eContentplus Programme

  4. Other example http://www.kartografie.nl/geometrics/Reference%20surfaces/body.htm Project funded by eContentplus Programme

  5. Example of cross-border inconsistency Fragment of the Dutch topo map showing the border of elgium and the Netherlands. The Mean Sea Level of Belgium differ -2.34m from the MSL of The Netherlands. As a result, contour lines are abruptly ending at the border. http://www.kartografie.nl/geometrics/Reference%20surfaces/body.htm Project funded by eContentplus Programme

  6. http://www.bkg.bund.de/nn_159884/EN/FederalOffice/Products/Reference__sys/NatRefHeight/EN__Height03__node.html__nnn=truehttp://www.bkg.bund.de/nn_159884/EN/FederalOffice/Products/Reference__sys/NatRefHeight/EN__Height03__node.html__nnn=true Project funded by eContentplus Programme

  7. Use Case Diagram Dataset Provider #1 Offers terrain #1 Wants a unique seamless terrain User Offers terrain #2 Dataset Provider #1 Project funded by eContentplus Programme

  8. 2 – Terrain Modeling • TIN’s • Orthogonal grids • Level curves Project funded by eContentplus Programme

  9. TIN Terrain Terrain Triangles Triangles * 1-2 3-3 3-3 Vertices Segments 2-2 2-n Other point’s elevation estimation by planar interpolation z = ax+by+c Vertices Project funded by eContentplus Programme

  10. a/ Direct representation TRIANGLE (#triangle, #vertex1, #vertex2, #vertex3) VERTEX (#vertex, x, y, z) b/ Segment-oriented representation TRIANGLE (#triangle, #segment1, #segment2, #segment3) SEGMENT (#segment, #vertex1, #vertex2) VERTEX (#vertex, x, y, z) c/ Including more topology SEGMENT (#segment, #vertex1, #vertex2, #triangle1, #triangle2) Project funded by eContentplus Programme

  11. Orthogonal grid For instance, every 100 m Other point’s elevation estimation by bilinear interpolation z = axy+bx+cy+d Project funded by eContentplus Programme

  12. Contour levels Project funded by eContentplus Programme

  13. Terrain Level curves z * Level curve piece * Vertices x, y Contourlevels Other point’s elevation estimation based on neighbors, f.i. Gravity (Newton) interpolation Project funded by eContentplus Programme

  14. 3 – Various Fragmentation • Thematic fragmentation • Zonal fragmentation • Hybrid fragmentation Project funded by eContentplus Programme

  15. Layer FragmentationThematic Partitioning Electricity Database Building Database Parcel Database Project funded by eContentplus Programme

  16. Zonal FragmentationGeographic Partitioning Zone A Database Zone B Database Zone C Database Project funded by eContentplus Programme

  17. 4 – Coordinate Transformation X, Y X, Y Z Z Ellipsoid 1 Ellipsoid 2 Project funded by eContentplus Programme

  18. Two problems • General formulas : • X = f (x, y) • Y = g (x, y) • Z = h (x, y, z) • Point global identifiers • points already existing • points created in the integration process Project funded by eContentplus Programme

  19. 5 – Cross-border integration • Coordinate transformation, and then • Same model • TIN • Grid • Contour levels • Different models • General methodology Project funded by eContentplus Programme

  20. TIN integration • Construct a global TIN based on both TIN’s • New triangles (green) are created having vertices in both TIN’s Project founded by eContentplus Programme

  21. Grid integration • Different steps (f.i. 100m, and 50 yards) • Different orientations • Two solutions: • Create a new grid by interpolating the previous grid Transform everything into TIN’s Project founded by eContentplus Programme

  22. Contour levels • Different Mean Sea level (origin of contour lines) • Different interval • Two solutions • Create new contour levels by interpolating • Transform everything into TIN’s Project founded by eContentplus Programme

  23. Different models • Generic solution • Transform everything into TIN’s • Beware of intermediate triangles • Example: TIN + Grid Project funded by eContentplus Programme

  24. Example for Terrain Integration • Database A (Grid) • Database B (TIN’s) • Cross-border integration: Database AB • Transformation into TIN’s of database A by splitting square into triangles Project funded by eContentplus Programme

  25. Example of Terrain Integration TIN + Grid Boundary of B Boundary of A Database B Database A I n t e r m e d i a r y z o n e Project funded by eContentplus Programme

  26. Database A • Grid file representation • UTM co-ordinates • Type A ellipsoid • Sea level (z=0) in Jackson Harbour • Relations • A-Terrain (#terrain, #mesh) • A-Mash (#mesh, #nw-pt, #ne-pt, #se-pt, #sw.pt) • A-Point (#point, x, y, z) Project funded by eContentplus Programme

  27. Database B • TIN’s • Gauss co-ordinates • Type B ellipsoid • Sea level (z=0) in Johnson Harbour • Relations • B-Terrain (#terrain, #triangle) • B-Triangle (#triangle, #pt1, #pt2, #pt3) • B-Point (#point, x, y, z) Project funded by eContentplus Programme

  28. Database Terrain MatchingTerrain Continuity M a t c h i n g 2 t e r r a i n d a t a b a s e s E x c e r p o f 2 t e r r a i n d a t a b a s e s b y t r a n s f o r m i n g s q u a r e s i n t o t r i a n g l e s w h i c h a r e t o b e f e d e r a t e d a n d m a t c h e d a n d a d d i n g s o m e i n t e r m e d i a r y t r i a n g l e s Project funded by eContentplus Programme

  29. Database AB • TIN’s • Gauss co-ordinates • Type B ellipsoid • Sea level (z=0) in Johnson Harbour • Global identifiers, even for additional triangles • Relations • AB-Terrain (#terrain, #triangle) • AB-Triangle (#triangle, #pt1, #pt2, #pt3) • AB-Point (#point, x, y, z) Project funded by eContentplus Programme

  30. Vertex/triangle identifiers: example • For database A • C.identifier = 1 000 000 + A.identifier • For database B • C.identifier = 2 000 000 + B.identifier • Intermediate zone • C.identifier = 3 000 000 + x Project funded by eContentplus Programme

  31. 6 – Final Remarks • Cross-border integration for seamless terrains is very awkward • Transformation of coordinates • Transformation of models • TIN is generally the best output model • Necessity of creating a fresh database, or a view above existing datasets • Problem of global identifiers Project funded by eContentplus Programme

  32. References • LAURINI R. (1998) Spatial Multidatabase Topological Continuity and Indexing: a Step towards Seamless GIS Data Interoperability. International Journal of Geographical Information Sciences. Vol. 12,4, June 1998, pp. 373-402. See slides on http://lisi.insa-lyon.fr/~laurini/resact/feder/FEDER.pdf

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