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 Weghe

Department of GeographyGhent University

Outline

Sketch maps

original concept

extended ontology

geospatial sketch maps, moving point objects and lifelines

Lifeline representations

binary distinctions

typology

Conclusions

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.(Forbus et al., 2003)

Sketch maps

Ontology after Forbus et al.

sketch map

glyph

ink content

Sketch maps

sketch map

glyph

ink

stroke

content

assumptions of traditional pencil-and-paper sketching: one-handed input curvilinear drawing tool

Sketch maps

sketch map

glyph

ink

stroke

spatial temporal

content

spatial temporal thematic

Sketch maps

not stored on paper maps easily stored on digital information systems

Temporal Ink

Ink Point X

Ink Point Y

Ink Point Timestamp (s)

1,22 1,10 130,441,39 1,03 130,501,44 0,98 130,531,44 0,81 130,591,42 0,64 130,621,34 0,47 130,651,27 0,34 130,691,24 0,23 130,721,24 0,13 130,751,27 0,02 130,781,36 -0,20 130,841,40 -0,32 130,871,40 -0,57 130,941,41 -0,66 130,971,41 -0,75 131,001,43 -0,83 131,031,43 -1,01 131,131,45 -1,06 131,151,46 -1,10 131,191,46 -1,10 131,22

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

A lifeline example

Explicit vs. implicit representations

explicit representation

the lifeline is represented

as one or more glyphs

implicit representation

the lifeline is implied by

one or more glyhps and

their interrelations

Explicit vs. implicit representations

Continuous vs. discrete

spatial continuous

connected spatial ink

temporal continuous

simple continuous interval

temporal ink

spatial continuous

connected spatial ink

temporal discontinuous

gaps in temporal ink

spatial discontinuous

disconnected spatial ink

temporal discontinuous

gaps in temporal ink

Aligned vs. non-aligned

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

reference lifeline

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

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

Typology of lifeline representationsLifeline

Glyph(s)

Explicit

Aligned

Continuous

Scaled Distorted

Discrete

Non-aligned

Implicit

Aligned Non-aligned

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