42,951 research outputs found
Refining Coarse-grained Spatial Data using Auxiliary Spatial Data Sets with Various Granularities
We propose a probabilistic model for refining coarse-grained spatial data by
utilizing auxiliary spatial data sets. Existing methods require that the
spatial granularities of the auxiliary data sets are the same as the desired
granularity of target data. The proposed model can effectively make use of
auxiliary data sets with various granularities by hierarchically incorporating
Gaussian processes. With the proposed model, a distribution for each auxiliary
data set on the continuous space is modeled using a Gaussian process, where the
representation of uncertainty considers the levels of granularity. The
fine-grained target data are modeled by another Gaussian process that considers
both the spatial correlation and the auxiliary data sets with their
uncertainty. We integrate the Gaussian process with a spatial aggregation
process that transforms the fine-grained target data into the coarse-grained
target data, by which we can infer the fine-grained target Gaussian process
from the coarse-grained data. Our model is designed such that the inference of
model parameters based on the exact marginal likelihood is possible, in which
the variables of fine-grained target and auxiliary data are analytically
integrated out. Our experiments on real-world spatial data sets demonstrate the
effectiveness of the proposed model.Comment: Appears in Proceedings of the Thirty-Third AAAI Conference on
Artificial Intelligence (AAAI 2019
Mining large-scale human mobility data for long-term crime prediction
Traditional crime prediction models based on census data are limited, as they
fail to capture the complexity and dynamics of human activity. With the rise of
ubiquitous computing, there is the opportunity to improve such models with data
that make for better proxies of human presence in cities. In this paper, we
leverage large human mobility data to craft an extensive set of features for
crime prediction, as informed by theories in criminology and urban studies. We
employ averaging and boosting ensemble techniques from machine learning, to
investigate their power in predicting yearly counts for different types of
crimes occurring in New York City at census tract level. Our study shows that
spatial and spatio-temporal features derived from Foursquare venues and
checkins, subway rides, and taxi rides, improve the baseline models relying on
census and POI data. The proposed models achieve absolute R^2 metrics of up to
65% (on a geographical out-of-sample test set) and up to 89% (on a temporal
out-of-sample test set). This proves that, next to the residential population
of an area, the ambient population there is strongly predictive of the area's
crime levels. We deep-dive into the main crime categories, and find that the
predictive gain of the human dynamics features varies across crime types: such
features bring the biggest boost in case of grand larcenies, whereas assaults
are already well predicted by the census features. Furthermore, we identify and
discuss top predictive features for the main crime categories. These results
offer valuable insights for those responsible for urban policy or law
enforcement
AAPOR Report on Big Data
In recent years we have seen an increase in the amount of statistics in society describing different phenomena based on so called Big Data. The term Big Data is used for a variety of data as explained in the report, many of them characterized not just by their large volume, but also by their variety and velocity, the organic way in which they are created, and the new types of processes needed to analyze them and make inference from them. The change in the nature of the new types of data, their availability, the way in which they are collected, and disseminated are fundamental. The change constitutes a paradigm shift for survey research.There is a great potential in Big Data but there are some fundamental challenges that have to be resolved before its full potential can be realized. In this report we give examples of different types of Big Data and their potential for survey research. We also describe the Big Data process and discuss its main challenges
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