Geography Reference
In-Depth Information
Table 1 Itinerary information requested in both interview and diary sheets of WCTFS: a day trip
spatiotemporal events and activities
Location
name
Arrival
time
Duration
(h)
Purpose and activities including
destination
Extra
transport
Meals
bought
$
Spent
1
2
3
4
5
6
7
Under analysis it became increasingly clear that for individuals the absence of
data items, such as an individual arrival time, was an issue for many respondents.
Very few provided fully complete records. However, in general, the sample
number who did respond remained high enough that for many tabulations analysis
could still be meaningfully undertaken, and these analyses feature in Forer and
Simmons (
2011
). Nonetheless, the gaps were regrettable and undoubtedly reduced
accuracy, as did the provision of mis-estimated values such as arrival time or
duration.
Absences provide a more significant issue for the proposed analysis and visu-
alisation of full itineraries. This is due to the fact that a single omission breaks the
whole itinerary into two or more parts and disrupts the continuity of the indi-
vidual's known movement. Since failure to complete any particular items was both
frequent and predominantly generated by random absent-mindedness this com-
promised the ability to visualise and analysis the data in a comprehensive way. At
this point a thesis (and eventually this chapter) was born, dedicated to assess the
quality of what we had and infer what might be missing (Sun
2009
).
The aims of the reported research became to assess the spatiotemporal data quality
of a mainstream survey of individual movement, to map the patterns of gaps and
errors in the datasets, and finally to investigate the possibilities of filling the gaps and
enhancing the consistency in order to improve the data quality of the individual
records. From the beginning Hägerstrand's idea of the individual timeline (Häger-
strand
1970
) and his surrounding conceptualization of individual human lives and
choice/constraint were seen as a solid background framework. Viewed as ''an
innovative and instructive approach to the study of time, space, and human activi-
ties'' (Golledge and Stimson
1997
, p 268). Time-geography's concept of the space-
time path can help reveal the underlying structure of movement. That perspective,
and its associated conceptualisation of space-time constraints, underwrote the
space-time reasoning algorithms in this paper. While Hägerstrand's prisms are
typically used to illustrate what could be done in the future this approach seeks to
show what they could not do in the past and looks to rewrite the past with care.
