Representing Moving Point Objects in Geospatial Sketch Maps

1. Representing Moving Point Objects in Geospatial Sketch Maps 15th International Conference InterCarto-InterGISGhent, 3 July 2009 Matthias Delafontaine, Seyed Hossein Chavoshi and Nico Van de WegheDepartment of GeographyGhent University

2. Outline • Sketch maps • original concept • extended ontology • geospatial sketch maps, moving point objects and lifelines • Lifeline representations • binary distinctions • typology • Conclusions

3. Sketch maps • Long research tradition in spatial cognition, cognitive mapping • Diverse research functions / roles / goals • Definition • a map drawn from memory of a place a person has been (Horan, 1999) • a map drawn from observation (rather than from exact measurements) and representing the main features of an area (The Free Dictionary, 2009) • compact spatial representations that express the key spatial features of a situation for the task at hand, abstracting away the mass of details that would otherwise obscure the relevant aspects.(Forbuset al., 2003)

4. Sketch maps Ontology after Forbuset al.

5. Sketch maps • assumptions of traditional pencil-and-paper sketching: • one-handed input • curvilinear drawing tool

6. Sketch maps

7. Sketch maps •  not stored on paper maps •  easily stored on digital information systems Temporal Ink

8. Geospatial sketch maps and lifelines • Geospatial sketch maps • elements are drawn from a top view perspective • elements are drawn at an approximated spatial scale • moving objects can be represented as moving point objects (MPOs) • Lifeline • a continuous set of positions that an MPO occupies in space over a certain period of time

9. A lifeline example

10. Explicit vs. implicit representations explicit representation the lifeline is represented as one or more glyphs

11. Explicit vs. implicit representations implicit representation the lifeline is implied by one or more glyhps and their interrelations

12. Continuous vs. discrete spatial continuous connected spatial ink spatial continuous connected spatial ink spatial discontinuous disconnected spatial ink temporal continuous simple continuous interval temporal ink temporal discontinuous gaps in temporal ink temporal discontinuous gaps in temporal ink

13. Aligned vs. non-aligned reference lifeline positive alignment drawing order reflects the orientation of movement negative alignment drawing order reflects the reverse orientation of movement no alignment drawing order does not reflect the orientation of movement

14. Alignment at three levels • Three hierarchical levels of alignment: • inter-glyph alignment positive, negative, or not aligned • inter-stroke alignment positive, negative, or not aligned • intra-stroke alignment positive, negative, or not aligned

15. Scaled vs. distorted • Alignment can be considered the key qualitative relationship between drawing chronology and the underlying content • What about the quantitative correlations between temporal ink and temporal content? • spatial-scaled glyphs: spatial ink drawn at an approximated spatial scale (as we assumed for geospatial sketch maps) • time-scaled glyphs: approximated proportionality between temporal ink and temporal content (approximated temporal scale) • scaled lifeline glyphs allow for making inferences about relative speed and travel time

16. Typology of lifeline representations

17. Conclusions • We have • extended the concept of sketch maps and the related ontology with the notion of temporal ink • considered some important properties of lifeline representations according to this extended ontology • presented a basic typology of representations for individual lifelines in sketch maps • Opportunities for further extensions • to multiple lifelines • to spatiotemporal concepts beyond motion • to other forms of data acquistion beyond conventional sketching