Michal Isaacson

Sequence alignment as a method for human activity analysis in space and time.

Abstract This article introduces the method of sequence alignment as a tool for analyzing the sequential aspects within the temporal and spatial dimensions of human activities. Sequence alignment was first developed during the 1980s and employed by biochemists to analyze DNA sequences. Toward the end of the 1990s it was adapted for use in the social sciences. However, unlike other social sciences practitioners, geographers have not, until now, exploited this method. In contrast to traditional quantitative methods, sequence alignment, as its name suggests, is directly concerned with the order (sequence) of events, and is therefore well suited for the pursuit of time-geographic research. To demonstrate the merits of sequence alignment for geographic research, a database composed of forty space-time sequences of visitors who had visited the Old City of Akko (Israel) was used. The sequences were obtained by means of GPS devices, which were distributed among the visitors tracked and which they operated for the duration of their visit to the city. The sequences thereby obtained were aligned using ClustalG, a sequence alignment computer program. The result of this analysis was the identification of three temporal-spatial time geographies of the visitors that were sampled in this study.

Life-Stage and Mobility: An Exploratory GPS Study of Mobility in Multigenerational Families, Ahmedabad, India.

As the population of older adults in India grows, research is needed to plan a sustainable future for India’s older adults. This article reports results from a Global Positioning System (GPS)–based pilot study that examined the mobility of middle-class, older adults living in Ahmedabad, Gujarat, India. Using mobility as a lens through which to examine the lives of older adults, we map potential research and identify policy areas of interest considering older adults in urban India. The study explores the role of life stage in mobility as well as the effects of gender and urban environment on mobility. Using this distinctive perspective on day-to-day life, we propose themes through which, using policy and planning tools, the living environments of older adults in Indian cities can be improved. These policy measures include focusing on walkability and pedestrian safety in residential areas and building on existing mixed land use to create high accessibility to goods and services in urban environments.

Using global positioning system to assess walking capacity.

TO THE EDITOR: Re: Barzilay Y, Noam S, Meir L, et al. Assessing the outcomes of spine surgery using global positioning systems. Spine (Phila Pa 1976) 2011;36:E263–7. We read with a great interest the study of Barzilay et al 1 that examined in two patients undergoing spine surgery whether surgical outcomes could be assessed objectively using a GPS. GPS data were recorded from unconstrained free-living measurements during a 6-week period. From these measurements, the authors computed several walking parameters as walking distances or speeds, and an index named “claudication index”: the maximum distance walked before the patient needed to stop and rest. However, many external events can interfered within the patient’ walk in his/her own environment (waiting at a traffi c light, meeting a friend...) and we wonder how it can be ascertained that this “maximum distance” was truly symptom-limited. In addition, with a GPS recording at a sampling rate of 0.1 Hz (one recording every 10 seconds), it cannot be excluded, and quite likely, that short resting bouts ( < 20 seconds) will be missed and incorporated into walking bouts, thus artifi cially increasing the “claudication index.” Although the GPS is a very promising tool to assess walking capacity, our experience shows that validation studies, as well as feasibility studies with large sample of subjects, are required before the GPS technique can be used as a routine. 2 , 3