Background: There is increasing interest in examining the influence of the built environment on physical activity. High-resolution data in a geographic information system is increasingly being used to measure salient aspects of the built environment and studies often use circular or road network buffers to measure land use around an individual's home address. However, little research has examined the extent to which the selection of circular or road network buffers influences the results of analysis.

GIS eased into geography without much discord until the 1990s, when a flurry of commentaries about the relative merits of GIS made their way into a number of geographic journals. The ensuing decade was marked by varying degrees of friction between GIS practitioners and their critics in human geography. Despite the methodological chasm between the two groups, little discussion of the implications of these differences has ensued. This article fills that gap with a historiographic examination of critiques of GIS. Critiques of GIS are organized into three waves or periods, each characterized by distinct arguments. The first wave, from 1990 to 1994, was marked by the intensity of debate as well as an emphasis on positivism. By 1995, the conversation waned as the number of critics grew, while GIS practitioners increasingly declined comment. This second wave marked the initiation of a greater degree of co-operation between GIS scholars and their critics, however. With the inception of the National Center for Geographic Information Analysis (NCGIA) Initiative 19, intended to study the social effects of GIS, many critics began to work closely with their peers in GIS. In the third wave, critiques of GIS expressed a greater commitment to the technology. Throughout the decade, debates about the technology shifted from simple attacks on positivism to incorporating more subtle analyses of the effects of the technology. These critiques have had considerable effect on the academic GIS community but are presently constrained by limited communication with GIS practitioners because of the absence of a common vocabulary. I argue that, if critiques of GIS are to be effective, they must find a way to address GIS researchers, using the language and conceptual framework of the discipline.

Area-based deprivation indices (ABDIs) have become a common tool with which to investigate the patterns and magnitude of socioeconomic inequalities in health. ABDIs are also used as a proxy for individual socioeconomic status. Despite their widespread use, comparably less attention has been focused on their geographic variability and practical concerns surrounding the Modifiable Area Unit Problem (MAUP) than on the individual attributes that make up the indices. Although scale is increasingly recognized as an important factor in interpreting mapped results among population health researchers, less attention has been paid specifically to ABDI and scale. In this paper, we highlight the effect of scale on indices by mapping ABDIs at multiple census scales in an urban area. In addition, we compare self-rated health data from the Canadian Community Health Survey with ABDIs at two census scales. The results of our analysis confirm the influence of spatial extent and scale on mapping population health-with potential implications for health policy implementation and resource distribution.KEYWORDS Deprivation indices, MAUP, Population health, Scale. A BRIEF BIOGRAPHY OF POPULATION HEALTH INDICES COMMONLY USED IN CANADAThe use of census data to quantify socioeconomic deprivation is a generally wellaccepted method of identifying populations with poorer health outcomes.1-5 The history of census-based area deprivation indices dates back to at least until 1971, when the Department of the Environment (DOE) in the United Kingdom used data taken from the census to identify localities where a high proportion of households were exposed to adverse social and economic conditions. 6 The indices were developed to more effectively identify areas in need of resources to improve quality of life. Publications stemming from The Black Report, 7 the Whitehall, 8 and Acheson studies 9 launched additional public scrutiny of the relationship between socioeconomic gradients and health status. These studies have spurred a relatively new yet increasingly popular framework that uses socioeconomic data taken from the census to quantify deprivation and demonstrate its relationship with population health. 2,[10][11][12][13][14] Schuurman, Bell, and Oliver are with the

Ensuring equity of access to primary health care (PHC) across Canada is a continuing challenge, especially in rural and remote regions. Despite considerable attention recently by the World Health Organization, Health Canada and other health policy bodies, there has been no nation‐wide study of potential (versus realized) spatial access to PHC. This knowledge gap is partly attributable to the difficulty of conducting the analysis required to accurately measure and represent spatial access to PHC. The traditional epidemiological method uses a simple ratio of PHC physicians to the denominator population to measure geographical access. We argue, however, that this measure fails to capture relative access. For instance, a person who lives 90 minutes from the nearest PHC physician is unlikely to be as well cared for as the individual who lives more proximate and potentially has a range of choice with respect to PHC providers. In this article, we discuss spatial analytical techniques to measure potential spatial access. We consider the relative merits of kernel density estimation and a gravity model. Ultimately, a modified version of the gravity model is developed for this article and used to calculate potential spatial access to PHC physicians in the Canadian province of Nova Scotia. This model incorporates a distance decay function that better represents relative spatial access to PHC. The results of the modified gravity model demonstrate greater nuance with respect to potential access scores. While variability in access to PHC physicians across the test province of Nova Scotia is evident, the gravity model better accounts for real access by assuming that people can travel across artificial census boundaries. We argue that this is an important innovation in measuring potential spatial access to PHC physicians in Canada. It contributes more broadly to assessing the success of policy mandates to enhance the equitability of PHC provisioning in Canadian provinces.

Access to high quality acute trauma care is well established across parts of Canada but a clear urban/rural divide persists. Regional efforts to improve short- and long-term outcomes after severe trauma should focus on the optimization of access to pre-hospital care and acute trauma care in rural communities using locally relevant strategies or novel care delivery options.