How Officers Create Guardianship: An Agent‐based Model of Policing

Crime is a complex phenomenon, emerging from the interactions of offenders, victims, and their environment, and in particular from the presence or absence of capable guardians. Researchers have historically struggled to understand how police officers create guardianship. This presents a challenge because, in order to understand how to advise the police, researchers must have an understanding of how the current system works. The work presents an agent‐based model that simulates the movement of police vehicles, using a record of real calls for service and real levels of police staffing in spatially explicit environments to emulate the demands on the police force. The GPS traces of the simulated officers are compared with real officer movement GPS data in order to assess the quality of the generated movement patterns. The model represents an improvement on existing standards of police simulation, and points the way toward more nuanced understandings of how police officers influence the criminological environment.     

Prediction of Resource Volumes at Untested Locations Using Simple Local Prediction Models

This paper shows how local spatial nonparametric prediction models can be applied to estimate volumes of recoverable gas resources at individual undrilled sites, at multiple sites on a regional scale, and to compute confidence bounds for regional volumes based on the distribution of those estimates. An approach that combines cross-validation, the jackknife, and bootstrap procedures is used to accomplish this task. Simulation experiments show that cross-validation can be applied beneficially to select an appropriate prediction model. The cross-validation procedure worked well for a wide range of different states of nature and levels of information. Jackknife procedures are used to compute individual prediction estimation errors at undrilled locations. The jackknife replicates also are used with a bootstrap resampling procedure to compute confidence bounds for the total volume. The method was applied to data (partitioned into a training set and target set) from the Devonian Antrim Shale continuous-type gas play in the Michigan Basin in Otsego County, Michigan. The analysis showed that the model estimate of total recoverable volumes at prediction sites is within 4 percent of the total observed volume. The model predictions also provide frequency distributions of the cell volumes at the production unit scale. Such distributions are the basis for subsequent economic analyses.

Crustal and upper mantle structure of the northwestern North Island, New Zealand, from seismic refraction data

The crustal and upper mantle structure of the northwestern North Island of New Zealand is derived from the results of a seismic refraction experiment; shots were fired at the ends and middle of a 575 km-long line extending from Lake Taupo to Cape Reinga. The principal finding from the experiment is that the crust is 25 ± 2 km thick, and is underlain by what is interpreted to be an upper mantle of seismic velocity 7.6 ± 0.1 km s⁻¹, that increases to 7.9 km s⁻¹ at a depth of about 45 km. Crustal seismic velocities vary between 5.3 and 6.36 km s⁻¹ with an average value of 6.04 km s⁻¹. There are close geophysical and geological similarities between the north-western North Island of New Zealand and the Basin and Range province of the western United States. In particular, the conditions of low upper-mantle seismic velocities, thin crust with respect to surface elevation, and high heat-flow (70–100 mW m⁻²) observed in these two areas can be ascribed to their respective positions behind an active convergent margin for about the past 20 Myr.     

Simulating the effect of Nitrogen application on Wheat Yield by linking remotely sensed measurements with wtgrows simulation model

A field experiment was conducted on wheat at New Delhi with five treatments of Nitrogen (N) fertilizer application (0, 30, 60, 90 and 120 kgha^-1). Relationship has been established between observed leaf area index (LAI) and remotely sensed vegetation indices. These relationships are inverted and used for predicting LAI from vegetation indices on different days after sowing. The “re-initialization” strategy is implemented in model WTGROWS in which initial conditions of model are changed so that the model simulated LAI match remote sensing predicted LAI. The model performance with re-initialization has been evaluated by comparing the simulated grain yield and total above-ground dry matter (TDM) values with the actual observations. The results show that in-season re-initialization is effective in model course correction by improving the simulated results of yield and TDM for different N treatments even though the model was run with no N stress condition. Model re-initialization at different days shows that the closer is the day of re-initialization to crop anthesis the more effective is model course correction. Also, the treatment showing maximum error in yield simulation without re-initialization shows maximum reduction in error by re-initialization. The approach shows that the remote sensing inputs can substitute for some of the inputs or errors in inputs required by crop models for yield prediction.     

Geometry and accuracy of reflecting points in bistatic satellite altimetry

The analysis of the time and space distribution of specular (reflecting) points in bistatic altimetry between GPS and CHAMP satellites or SAC-C (taken as examples) is extended from Wagner and Klokočník (2003 J. Geod 77: 128–138). We demonstrate a significantly higher number and density of reflecting points in bistatic altimetry in comparison with traditional monostatic altimetry. After an outline of our older accuracy assessment for the vertical position of the reflecting point, we add a new independent derivation and compare both approaches. We account for orbit errors of both the transmitters (GPS) and receiver (CHAMP) satellites, and the measurement (delay) error. We found that the accuracy of the vertical position of the reflecting point decreases only slowly with increasing off-nadir angle and that the orbit errors must be accounted for if decimeter and better accuracy is required. In this paper, we do not study errors such as state of the ocean, technical parameters of the receiving system, and atmospheric corrections.     

Interannual variability of low-degree gravitational change, 1980–2002

Time variations in the Earths gravity field at periods longer than 1 year, for degree-two spherical harmonics, C₂₁, S₂₁, and C₂₀, are estimated from accurately measured Earth rotational variations. These are compared with predictions of atmospheric, oceanic, and hydrologic models, and with independent satellite laser ranging (SLR) results. There is remarkably good agreement between Earth rotation and model predictions of C₂₁ and S₂₁ over a 22-year period. After decadal signals are removed, Earth-rotation-derived interannual C₂₀ variations are dominated by a strong oscillation of period about 5.6 years, probably due to uncertainties in wind and ocean current estimates. The model-predicted C₂₀ agrees reasonably well with SLR observations during the 22-year period, with the exception of the recent anomaly since 1997/1998.     

Dynamic survey of architectural heritage by high-speed microwave interferometry

The authors propose the use of a high-speed interferometric radar for remotely measuring both transient displacements and steady-state vibrations of architectural heritage structures in order to test their stability conditions. Demonstrative results of application of the technique to a prominent cultural heritage artwork, the tower of Giotto in Florence, Italy, are reported.     

Wet tropospheric effects on precise relative GPS height determination

Summary Considerable interest has been generated recently in the use of the Global Positioning System (GPS) for precise height determination. A major error source in these measurements is the propagation delay due to atmospheric water vapour. In order to achieve the high precisions required for such applications as absolute sea-level monitoring improvement of wet delay modelling is necessary. Results from a GPS campaign show a significant correlation (0.91) between the variability of the wet delay measured using a water vapour radiometer (WVR) at the Onsala site and the absolute value of the residual error in the height determination of a 134 km baseline from Onsala to Jönköping. This correlation indicates that the atmosphericvariability as inferred from the WVR data includes information on the quality of the GPS height estimate. During periods of high atmospheric activity, e.g., during the passage of a weather front, the use of a six-parameter gradient model reduces the spread for the vertical coordinate from 40 mm to 20 mm (with standard deviations of 17 mm and 9 mm respectively) over the 134 km baseline (less than 1 × 10^–7) using 8 hour data spans on 11 different days over a six month period.