Posts Tagged ‘Marceau’

Temporal GIS do we go back, or only forward?

Thursday, March 14th, 2013

Marceau et al.’s paper on temporal topology in GIS Databases outlines the faults with temporal GIS which seems echoes Marceau’s earlier paper on spatial GIS and its faults within social and natural sciences. In both temporal and spatial GIS, as I compare the two papers, the resolution seems to be one of the main issues affecting the accuracy of topology. To clarify, in spatial GIS, higher resolution reflects more data acquired and more accurate spatial topology; while in temporal GIS, higher resolution reflects a higher rate of sampling versus change in the area and more accurate temporal topology. To simplify, when dealing with temporal GIS, it comes down to the sample rate and what is included within the sample and thus, as talked about in spatial scale the “politics of scale”.

I believe that Marceau et al. tried to address the intervals of sampling, however I believe, from everything I have read on scale and scale changes, that Marceau et al.’s approach may be fatally flawed in that it is too simple to transfer to larger areas with greater variability of change. The method once upscaled will produce uncertainties if not greater uncertainties then what was already have within there study area. In essence, it is the “politics of scale”, were the question on how temporal GIS operates or can operate within a software platform, is mired in uncertainty by the data collected over time and the modification by Marceau et al. during the application of the data within a platform setting.

For temporal GIS, it may be impossible to go back in time to map. GIScience may have to start new from the present time working into the future. Therefore, GIScientists will know, now that platforms exist, that certain data sets need to be created that can represent the change rather then extrapolation into the past, which is inherently uncertain without wide-scale identifiers present (i.e. Land survey archeology or the process of digging into the ground to identify past land-uses for topology identifiers).



Tipping the scale toward “science”

Thursday, February 14th, 2013

Marceau’s sums up issues pertaining to the variability in scale including scale dependence, scale domains and scale thresholds. At the crux of the article is an illustration of “a shift in paradigm where entities, patterns and processes are considered as intrinsically linked to the particular scale at which they can be distinguished and defined” (Marceau 1999). The need in any science to be wary of the scale at which the given work is conducted or phenomenon observed is absolutely (and relatively) critical. Different phenomena occur at different scales, and significant inaccuracies in the data exist if this is not accounted for.

I have no qualms with most of Marceau’s article. However, I would like to address another little assertion the author makes in her conclusion: the shift in paradigm once more toward a “science of scale.” After our discussion a few weeks ago regarding rethinking GIS as a science, in addition to a tool, this struck me as particularly interesting. In its broadest sense, science is a body of rationally explained and testable knowledge. Understanding scale as a scientific field in this regard is difficult. I have no problem with comprehending and accepting scale as a basic property of science, but separating out scale as its own entity?

That said, accounting for all of the work involved in understanding thresholds and dependence and the role that a varying scale can play on the world is not trivial. I simply feel that whereas there are laws of physics, for instance, there is no singular body of accepted knowledge, as far as I know, surrounding scale, with the exception that scale is a property of a phenomenon that must be noted and maintained as much as possible.

– JMonterey