Trend surface analysis of geographic flows

An origin-destination (OD) flow is the movement of objects from an origin to a destination. Determining how flows vary across geographic locations helps understand mechanism distributions; however, it has rarely been studied. Here, we propose trend surface model with polynomial functions quantify distribution coordinates in space. This assumes that observed data-record composed value and residual, represented by orthogonal O D as independent variables properties dependent variables. The simulation experiments based on linear quadratic models indicated function could reflect increasing/decreasing variation OD (i.e. trends) different patterns. Applying this case study taxi broad Central Business District Beijing, found exhibited rising toward southwest. characteristics are associated distributions urban functional patches, where workplaces residences increased southwest area. Notably, spatial deviations can help identifying site pairs attract at high density (e.g. commerce centers big communities), facilitating planning public transportation mitigate congestion.