Issue link: https://read.dmtmag.com/i/78956
The rub is that most of the user community and much of the vector-based GIS'ers are unaware of fixed roving windows, let alone weighted and dynamic windows. However, the utility of these advanced procedures in conceptualizing geographic space within context of its surroundings is revolutionary. an ameba-like shape to identify data values to be summarized—the pseudopods change shape and extent at each instantaneous location. The result is a localized summary of data, such as proximity to human activity within preferential reach of each grid location to characterize animal/human interac- tion potential. A combination of window considerations also can be applied, including the following: 1. Preferentially weighting fuel loadings. 2. Areas along downhill locations. 3. As a function of slope, with steep areas reach- ing farther away than gently sloped areas. In a wildfire risk model, the resultant "roving- window" summary would favor fuel conditions within the elongated pseudopods of the steeply sloped downhill locations. Line-of-Sight Connectivity A third type of dynamic consideration involves line- of-sight connectivity, where the "viewshed" of a location within a specified distance is used to define a roving window (see Figure 3). In a military situation, this type of window might be useful in summarizing the likelihood of enemy activity that's visually con- nected to each map location. Areas with high visual exposure levels within the dynamic window are poor places to set up camp, but ideal places for establish- ing forward-observer outposts. A less war-like application of line-of-sight windows involves terrain analysis. Areas not seen are "over Figure 2. Uphill, downhill and across portions of a roving window can be determined by considering the relative values on a 3-D surface. the hill" in a macro-sense for ridge lines and "in a slight depression" in a micro-sense for potholes. If all locations are seen, then there's minimal macro or micro terrain variations. The rub is that most of the user community and much of the vector-based GIS'ers are unaware of fixed roving windows, let alone weighted and dynamic windows. However, the utility of these advanced pro- cedures in conceptualizing geographic space within context of its surroundings is revolutionary. The view through a dynamic window is quite useful, but it's initially mind-boggling … see you on the other side. Author's Notes: 1) See Topic 11, Characterizing Micro-Terrain Features, "Characterizing Local Terrain Conditions"; 2) Topic 26, Characterizing Micro-Terrain Features, "Nearby Things Are More Alike"; and 3) Topic 25, Calculating Effective Distance and Connectivity, "Measuring Distance Is Neither Here nor There," in the online book, Beyond Mapping III, at www.innovativegis.com/basis/MapAnalysis. Figure 3. A line-of-sight window identifies locations that are "seen" and "not seen" from the window's focus. AUGUST 2O12 / WWW . GEOPLA CE . COM 11