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Path-Based Plan Generation for Navigation Using Map Data

This lecture introduces a framework for generating directions based on path-based and message-based planning concepts. It outlines the architecture of a GIS system that utilizes map data files containing details about buildings, routes, and waypoints. Key attributes like location, street names, and coordinates are emphasized. The process includes computing path plans from start to end nodes using operators that represent paths between intersection points. The search algorithms for route generation are discussed, emphasizing the importance of effective data structures while avoiding infinite recursion.

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Path-Based Plan Generation for Navigation Using Map Data

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  1. Generating Directions Lecture 2 Map Data Path Based Plan Generating Directions

  2. Before we start • NDA • mdina.zip (for a few days) Generating Directions

  3. Sentence Planner Path Planner Text Planner Realisation Proposed Architecture GIS Map Query Path Based Plan Message Based Plan Sentence Plan Text Generating Directions

  4. Map Data Files • These exist 3 data files with tab separated data inside them. • These files describe • Buildings • Routes (ie streets) • Way points: points on streets • Minor errors in data (St. names) Generating Directions

  5. Buildings Example: MDINA 1 TRIQ VILLEGAIGNON 0 MDINA DUNGEON O 35.845252 14.369577 Attributes in order • Location: char(32) • Building ID: int • Street Prefix: char(15) • Street Name: char(80) • Building Number: int • Building Name: char(10) • Building Proper Name: char (80) • Building Type: char(1) C:commercial, O: other • X coord and y coord:float Generating Directions

  6. Routes Example: MDINA 1 SQAQ ARAGONA RBT 12 Attributes in this order: • Location: char(32) • Route ID: int • Street Prefix:char(15) • Street Name:char(80) • Postcode:char(8) Generating Directions

  7. Routes Way Points Examples 1 MDINA 1 SQAQ ARAGONA RBT 12 35.766601 14.399467 2 MDINA 1 SQAQ ARAGONA RBT 12 35.770655 14.401142 • Attributes in order • Way Point ID: number • Location: char(32) • Route ID: number • Street Prefix: char (15) • Street Name: char(80) • Postcode: char(8) • X coord and Y coord:float Generating Directions

  8. Summary • Route way points give you enough description of intersections and roads • ‘Buildings’ files gives you info on which road they reside, just missing route id • Thus it is possible to build description of buildings when traversing route. • A subtask will be to build your system to describe buildings while going through just one road Generating Directions

  9. Search Problem • Given start and goal positions, compute path-based plan. • State-based search • start node • end node • operators • search strategy Generating Directions

  10. Start and End Nodes • Can be specified in any reasonable way e.g. • Coordinates • Building • Point of intersection • Waypoint Generating Directions

  11. Operators • Operator = state to state transformation • Consider each operator to be a path between adjacent points of intersection. • Operator data structure minimally contains start and end points. • Later details of journey can be added (buildings etc.) Generating Directions

  12. Method • Define classes: point; path; plan .... • Compute all intersection points from map data. • Compute set of "operators" (paths) = journeys between adjacent intersection points • Find intersection points nearest start and goal. • Search for spanning path using paths between intersection points. Generating Directions

  13. Search • Algorithm which checks which road to go through to arrive from point A to point B. • You will need appropriate algorithms or data structures for intersections. • Start off using brute force search. • Watch out for infinite recursions! • This should give you a route through a series of route ids. • See Russell & Norvig (2003) for details of search algorithms. Generating Directions

  14. Taken from Russell & Norvig 2003 Generating Directions

  15. Next • Elaboration of Path-Based Plan • Path-Based Plan => Message Based Plan. Generating Directions

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