Networks in GIS

1. Networks in GIS • Network model • Flow on Networks • Hydrologic networks • Linear referencing on networks Some slides in this presentation were prepared by Dr Francisco Olivera

2. Network Definition • A network is a set of edges and junctions that are topologically connected to each other.

3. Network Model in GIS • Three components • Geometric model: (x,y,z,m) coordinates of edges and junctions • Logical model: which edges are connected to what junctions • Addressing model: location on the network using measure

4. Edges and Junctions • Simple feature classes: points and lines • Network feature classes: junctions and edges • Edges can be • Simple: one attribute record for a single edge • Complex: one attribute record for several edges in a linear sequence • A single edge cannot be branched No!!

5. Polylines and Edges

6. Junctions • Junctions exist at all points where edges join • If necessary they are added during network building (generic junctions) • Junctions can be placed on the interior of an edge e.g. stream gage • Any number of point feature classes can be built into junctions on a single network

7. Build Network Tables • Establishes connectivity of Edge and Junction features • Enables tracing • Generates Generic Junctions Geometric Network Wizard in ArcCatalog

8. Snapping Features

9. Network Sources and Sinks Each junction feature class in a network can have junctions which are sources or sinks for flow

10. Ancillary Role of Sink

11. Flow to a sink

12. Flags

13. Trace Solvers

14. Upstream Trace Solvers

15. Hydrologic Networks • Hydrologic data includes: • Single-line streams • Double-line streams • Braided streams • Manmade channel systems • Waterbodies

16. Concepts from Fluid Mechanics

17. Location of the Flowline

18. Flow Line Traces movement of water in a one-dimensional flow system

19. Introduction to the Hydro Network • Hydro Edge – think of Arc • HydroJunction – think of Node • Waterbody – think of Polygon

20. Edge Junction Flow Network A connected set of flow edges

21. Hydro Network Flow Network + Shorelines

22. Network Building • Define flow-paths within double-line streams and waterbodies. • Define network sinks and sources.

23. Network Connectivity Find connected Find loops

24. Network Flow Direction • Enable flow in flow-paths. • Disable flow in shorelines Sink Flow direction is unknown

25. Network Flow Direction • Enable flow in flow-paths. • Disable flow in shorelines Sink Flow direction is known

26. Uninitialized Flow Direction

27. Assigned Flow Direction

28. Network Tracing Trace Upstream Trace Downstream

29. Trace Path Find the shortest path between two points on the network

30. Hydro Network for Holland

31. Hydro Network for Colorado River Basin around Lake Travis

32. Schematic Network

33. Connecting Drainage Areas to the Network Area goes to point on line

34. Linear Referencing(Requires ArcInfo 8.1) Where are we on a line?

35. My Streams are really long… Use ReachID to link many Hydro Edges together into one River

36. Addressing

37. Coordinates of a 2-D Polyline

38. Coordinates of a 2-D Polyline M

39. Setting Line Measure

40. Proportional Aliasing Distance is measured Relative to the length of the line as a percentage 0% – 100%

41. Setting Percent Measure pMSeg.SetAndInterpolate MsBetween 0, 100 pMSeg.SetAndInterpolate MsBetween 100, 0 0 – 100 going downstream 0 – 100 going upstream

42. Distances from Upper End in Meters

43. 0% Percent distance from bottom end of reach 100%

44. Measure in kilometers Measure in km from bottom end of line (like river miles or Kilometers) pMSeg.SetAndInterpolateMsBetween 0, ([Shape_Length] /1000)

45. Point Events on a Line A point event is located on a line at a particular measure value

46. Point and Line Events

47. Displaying Events