UNDERSTANDING SPATIAL INERTIA: CENTER OF GRAVITY,POPULATION DENSITIES,THE WEBER PROBLEM,AND GRAVITY POTENTIAL*

ABSTRACT. In this paper we attempt to clarify the theoretical links between the concepts of “center of gravity” and “point of maximum population density” which describe the present, and the concepts of “minimum of the comprehensive Weber problem” and “maximum comprehensive gravity potential” which guide the future. Critical values of the characteristic parameters of the relevant functions are estimated. Implications for the understanding of spatial inertia are discussed.     

Spatial Cluster Detection in Spatial Flow Data

As a typical form of geographical phenomena, spatial flow events have been widely studied in contexts like migration, daily commuting, and information exchange through telecommunication. Studying the spatial pattern of flow data serves to reveal essential information about the underlying process generating the phenomena. Most methods of global clustering pattern detection and local clusters detection analysis are focused on single‐location spatial events or fail to preserve the integrity of spatial flow events. In this research we introduce a new spatial statistical approach of detecting clustering (clusters) of flow data that extends the classical local K‐function, while maintaining the integrity of flow data. Through the appropriate measurement of spatial proximity relationships between entire flows, the new method successfully upgrades the classical hot spot detection method to the stage of “hot flow” detection. Several specific aspects of the method are discussed to provide evidence of its robustness and expandability, such as the multiscale issue and relative importance control, using a real data set of vehicle theft and recovery location pairs in Charlotte, NC.     

Palaeochannels of the Balkh river (northern Afghanistan) and human occupation since the Bronze Age period

In 2002, the unexpected discovery of Hellenistic architectural blocks, buried in 8 m of alluvium, found displaced in a former bed of the river of Balkh, brought about a programme of surveys and excavations under the aegis of the French Archaeological Mission in Bactria. The geoarchaeological side of the programme focused on the drawing of a regional geomorphological map then on the identification, mapping and dating of the palaeochannels of the river of Balkh. We established the chronology of several fluvial channel generations by association with archaeological settlements of different eras (Bronze Age, Bactro-Achaemenid period, Kushan period, Islamic period) and with optically stimulated luminescence dating carried out on alluvium deposits. The present riverbed leading up to Aqcha was formed during the Islamic period. We suspect the primary agent of this change in the river channel to, be tectonic activity and the activation of a blind fault crossing the floodplain. We identified a northern Bactro-Achaemenid aqueduct, currently located in the desert area separating the plain of Balkh from the Amu Darya.     

Geoarchaeology of Sidon's ancient harbours,Phoenicia

Geoarchaeological data from Sidon's ancient harbour areas elucidate six evolutionary phases since the Bronze Age. (1) At the time of Sidon's foundation, during the third millennium BC, medium sand facies show the city's northern and southern pocket beaches to have served as proto-harbours for Middle to Late Bronze Age societies. (2) Towards the end of the Late Bronze Age and the Early Iron Age, expanding international trade prompted coastal populations into modifying these natural anchorages. In Sidon's northern harbour, transition from shelly to fine-grained sands is the earliest granulometric manifestation of human coastal modification. The lee of Zire island was also exploited as a deep-water anchorage, or outer harbour, at this time. (3) Although localised sediments evoke developed port infrastructure during the Phoenician and Persian periods, high-resolution reconstruction of the northern harbour's Iron Age history is problematic given repeated dredging practices during the Roman and Byzantine periods. (4) Fine-grained silts and sands in the northern harbour are coeval with advanced Roman engineering works, significantly deforming the coastal landscape. Bio- and lithostratigraphical data attest a leaky lagoon type environment, indicative of a well-protected port. (5) The technological apogee of Sidon's northern harbour is recorded during the late Roman and Byzantine periods, translated stratigraphically by a plastic clays unit and brackish lagoon fauna. (6) A final semi-abandonment phase, comprising coarse sand facies, concurs silting up and a 100–150 m progradation of the port coastline after the seventh century AD. We advance three hypotheses to explain these stratigraphic data, namely cultural, tectonic and tsunamogenic. Finally, our results are compared and contrasted with research undertaken in Sidon's sister harbour, Tyre.     

Recent Advances in Moche Archaeology

The discovery of the royal tombs at Sipán in 1987 propelled Moche archaeology to the forefront of Andean studies. In the last decade, the study of Moche political organization and ideology through public architecture, cultural remains, funerary patterns, and iconography has forced the revision of previous conceptions about Moche state formation, urbanism, and the functioning of this complex society. Major advances in iconography, internal organization of urban centers, temples and domestic architecture, craft production, and mortuary patterns are embedded in a new chronology that supports a longer development and a more gradual collapse. The recognition of Moche as the first state in South America is still valid, but its monolithic character is rejected in favor of several autonomous polities. The number and size of potential Moche states are currently debated, as is the role of warfare and ideology in Moche state formation.     

Spatial Autocorrelation Statistics of Areal Prevalence Rates under High Uncertainty in Denominator Data

We propose a new estimator of spatial autocorrelation of areal incidence or prevalence rates in small areas, such as crime and health indicators, for correcting spatially heterogeneous sampling errors in denominator data. The approach is dubbed the heteroscedasticity‐consistent empirical Bayes (HC‐EB) method. As American Community Survey (ACS) data have been released to the public for small census geographies, small‐area estimates now form the demographic landscape of neighborhoods. Meanwhile, there is growing awareness of the diminished statistical validity of global and local Moran’s I when such small‐area estimates are used in denominator data. Using teen birth rates by census tracts in Mecklenburg County, North Carolina, we present comparisons of conventional and new HC‐EB estimates of Global and Local Moran’s I statistics created on ACS data, along with estimates on ground truth values from the 2010 decennial census. Results show that the new adjustment method dramatically enhances the statistical validity of global and local spatial autocorrelation statistics.     

flowAMOEBA: Identifying Regions of Anomalous Spatial Interactions

This study aims at developing a data‐driven and bottom‐up spatial statistic method for identifying regions of anomalous spatial interactions (clusters of extremely high‐ or low‐value spatial flows), based on which it creates a spatial flow weights matrix. The method, dubbed flowAMOEBA, upgrades a multidirectional optimum ecotope‐based algorithm (AMOEBA) from areal data to spatial flow data through a proper spatial flow neighborhood definition. The method has the potential to dramatically change the way we study spatial interactions. First, it breaks the convention that spatial interaction data are always collected and modeled between spatial entities of the same granularity, as it delineates the OD region of anomalous spatial interactions, regardless of the size, shape, scale, or administrative level. Second, the method creates an empirical spatial flow weights matrix that can handle network autocorrelation embedded in spatial interaction modeling, thus improving related policy‐making or problem‐solving strategies. flowAMOEBA is tested and demonstrated on a synthetic data set as well as a county‐to‐county migration data set.