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result(s) for
"Stevens, Forrest"
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Disaggregating Census Data for Population Mapping Using Random Forests with Remotely-Sensed and Ancillary Data
by
Stevens, Forrest R.
,
Tatem, Andrew J.
,
Linard, Catherine
in
Algorithms
,
Cambodia
,
Case studies
2015
High resolution, contemporary data on human population distributions are vital for measuring impacts of population growth, monitoring human-environment interactions and for planning and policy development. Many methods are used to disaggregate census data and predict population densities for finer scale, gridded population data sets. We present a new semi-automated dasymetric modeling approach that incorporates detailed census and ancillary data in a flexible, \"Random Forest\" estimation technique. We outline the combination of widely available, remotely-sensed and geospatial data that contribute to the modeled dasymetric weights and then use the Random Forest model to generate a gridded prediction of population density at ~100 m spatial resolution. This prediction layer is then used as the weighting surface to perform dasymetric redistribution of the census counts at a country level. As a case study we compare the new algorithm and its products for three countries (Vietnam, Cambodia, and Kenya) with other common gridded population data production methodologies. We discuss the advantages of the new method and increases over the accuracy and flexibility of those previous approaches. Finally, we outline how this algorithm will be extended to provide freely-available gridded population data sets for Africa, Asia and Latin America.
Journal Article
High Resolution Population Distribution Maps for Southeast Asia in 2010 and 2015
2013
Spatially accurate, contemporary data on human population distributions are vitally important to many applied and theoretical researchers. The Southeast Asia region has undergone rapid urbanization and population growth over the past decade, yet existing spatial population distribution datasets covering the region are based principally on population count data from censuses circa 2000, with often insufficient spatial resolution or input data to map settlements precisely. Here we outline approaches to construct a database of GIS-linked circa 2010 census data and methods used to construct fine-scale (∼100 meters spatial resolution) population distribution datasets for each country in the Southeast Asia region. Landsat-derived settlement maps and land cover information were combined with ancillary datasets on infrastructure to model population distributions for 2010 and 2015. These products were compared with those from two other methods used to construct commonly used global population datasets. Results indicate mapping accuracies are consistently higher when incorporating land cover and settlement information into the AsiaPop modelling process. Using existing data, it is possible to produce detailed, contemporary and easily updatable population distribution datasets for Southeast Asia. The 2010 and 2015 datasets produced are freely available as a product of the AsiaPop Project and can be downloaded from: www.asiapop.org.
Journal Article
Dynamic population mapping using mobile phone data
2014
During the past few decades, technologies such as remote sensing, geographical information systems, and global positioning systems have transformed the way the distribution of human population is studied and modeled in space and time. However, the mapping of populations remains constrained by the logistics of censuses and surveys. Consequently, spatially detailed changes across scales of days, weeks, or months, or even year to year, are difficult to assess and limit the application of human population maps in situations in which timely information is required, such as disasters, conflicts, or epidemics. Mobile phones (MPs) now have an extremely high penetration rate across the globe, and analyzing the spatiotemporal distribution of MP calls geolocated to the tower level may overcome many limitations of census-based approaches, provided that the use of MP data is properly assessed and calibrated. Using datasets of more than 1 billion MP call records from Portugal and France, we show how spatially and temporarily explicit estimations of population densities can be produced at national scales, and how these estimates compare with outputs produced using alternative human population mapping methods. We also demonstrate how maps of human population changes can be produced over multiple timescales while preserving the anonymity of MP users. With similar data being collected every day by MP network providers across the world, the prospect of being able to map contemporary and changing human population distributions over relatively short intervals exists, paving the way for new applications and a near real-time understanding of patterns and processes in human geography.
Journal Article
The spatial allocation of population: a review of large-scale gridded population data products and their fitness for use
by
Pistolesi, Linda
,
Comenetz, Joshua
,
Tatem, Andrew J.
in
Data
,
Disaster risk
,
Environmental health
2019
Population data represent an essential component in studies focusing on human–nature interrelationships, disaster risk assessment and environmental health. Several recent efforts have produced global- and continental-extent gridded population data which are becoming increasingly popular among various research communities. However, these data products, which are of very different characteristics and based on different modeling assumptions, have never been systematically reviewed and compared, which may impede their appropriate use. This article fills this gap and presents, compares and discusses a set of large-scale (global and continental) gridded datasets representing population counts or densities. It focuses on data properties, methodological approaches and relative quality aspects that are important to fully understand the characteristics of the data with regard to the intended uses. Written by the data producers and members of the user community, through the lens of the “fitness for use” concept, the aim of this paper is to provide potential data users with the knowledge base needed to make informed decisions about the appropriateness of the data products available in relation to the target application and for critical analysis.
Journal Article
High-resolution gridded population datasets for Latin America and the Caribbean in 2010, 2015, and 2020
by
Sorichetta, Alessandro
,
Stevens, Forrest R.
,
Tatem, Andrew J.
in
692/699/255/1629
,
704/172
,
704/844/685
2015
The Latin America and the Caribbean region is one of the most urbanized regions in the world, with a total population of around 630 million that is expected to increase by 25% by 2050. In this context, detailed and contemporary datasets accurately describing the distribution of residential population in the region are required for measuring the impacts of population growth, monitoring changes, supporting environmental and health applications, and planning interventions. To support these needs, an open access archive of high-resolution gridded population datasets was created through disaggregation of the most recent official population count data available for 28 countries located in the region. These datasets are described here along with the approach and methods used to create and validate them. For each country, population distribution datasets, having a resolution of 3 arc seconds (approximately 100 m at the equator), were produced for the population count year, as well as for 2010, 2015, and 2020. All these products are available both through the WorldPop Project website and the WorldPop Dataverse Repository.
Design Type(s)
data integration objective • database creation objective • time series design
Measurement Type(s)
population
Technology Type(s)
census
Factor Type(s)
Sample Characteristic(s)
Homo sapiens • Antigua and Barbuda • Argentina • Belize • Bolivia • Brazil • Chile • Colombia • Costa Rica • Cuba • Dominican Republic • Ecuador • El Salvador • French Guiana Region • Guatemala • Guyana • Haiti • Honduras • Jamaica • Mexico • Nicaragua • Panama • Paraguay • Peru • Puerto Rico • Suriname • Trinidad and Tobago • Uruguay • Venezuela • anthropogenic habitat
Machine-accessible metadata file describing the reported data
(ISA-Tab format)
Journal Article
Assessing long-term conservation impacts on adaptive capacity in a flagship community-based natural resources management area in Botswana
2023
Over the past three decades community-based natural resources management (CBNRM) has sought to address the concurrent needs of economic development and ecological protection at the local level, but there is often strong divergence between development and conservation interests and successes. In particular, CBNRM has not always led to expected socioeconomic outcomes, while information of its impact on human well-being at household level is sparse. In Botswana, most communities do not disburse benefits from CBNRM ventures to households. This leads to an inherent scale mismatch that arises because the costs of living with wildlife are felt at the household level, while the benefits are paid out at the community or village level. We use longitudinal data from two household surveys conducted 22 years apart to assess if benefits from the Botswana model of CBNRM have increased household-level adaptive capacity for those living with wildlife. We take a livelihoods capital approach to develop indicators of adaptive capacity and measure how livelihood diversity, inequality, and adaptive capacity have changed in five communities in northern Botswana between 1995 and 2017. Our analyses confirm the findings of qualitative reviews and suggest that CBNRM is under-performing in its contribution to improved household-level adaptive capacity. CBNRM cannot be said to benefit communities if the majority of community members do not experience increased well-being. We therefore recommend restructuring the governance models of CBNRM and other community conservation approaches to ensure that benefits are more directly targeted to actively participating households.
Journal Article
A simulated ‘sandbox’ for exploring the modifiable areal unit problem in aggregation and disaggregation
2024
We present a spatial testbed of simulated boundary data based on a set of very high-resolution census-based areal units surrounding Guadalajara, Mexico. From these input areal units, we simulated 10 levels of spatial resolutions, ranging from levels with 5,515–52,388 units and 100 simulated zonal configurations for each level – totalling 1,000 simulated sets of areal units. These data facilitate interrogating various realizations of the data and the effects of the spatial coarseness and zonal configurations, the Modifiable Areal Unit Problem (MAUP), on applications such as model training, model prediction, disaggregation, and aggregation processes. Further, these data can facilitate the production of spatially explicit, non-parametric estimates of confidence intervals via bootstrapping. We provide a pre-processed version of these 1,000 simulated sets of areal units, meta- and summary data to assist in their use, and a code notebook with the means to alter and/or reproduce these data.
Journal Article
Spatiotemporal patterns of population in mainland China, 1990 to 2010
2016
According to UN forecasts, global population will increase to over 8 billion by 2025, with much of this anticipated population growth expected in urban areas. In China, the scale of urbanization has, and continues to be, unprecedented in terms of magnitude and rate of change. Since the late 1970s, the percentage of Chinese living in urban areas increased from ~18% to over 50%. To quantify these patterns spatially we use time-invariant or temporally-explicit data, including census data for 1990, 2000, and 2010 in an ensemble prediction model. Resulting multi-temporal, gridded population datasets are unique in terms of granularity and extent, providing fine-scale (~100 m) patterns of population distribution for mainland China. For consistency purposes, the Tibet Autonomous Region, Taiwan, and the islands in the South China Sea were excluded. The statistical model and considerations for temporally comparable maps are described, along with the resulting datasets. Final, mainland China population maps for 1990, 2000, and 2010 are freely available as products from the WorldPop Project website and the WorldPop Dataverse Repository.
Design Type(s)
database creation objective • data integration objective • time series design • population modeling objective
Measurement Type(s)
population
Technology Type(s)
census
Factor Type(s)
Period
Sample Characteristic(s)
Homo sapiens • China • anthropogenic habitat
Machine-accessible metadata file describing the reported data
(ISA-Tab format)
Journal Article
Modelling Associations between Public Understanding, Engagement and Forest Conditions in the Inland Northwest, USA
2015
Opinions about public lands and the actions of private non-industrial forest owners in the western United States play important roles in forested landscape management as both public and private forests face increasing risks from large wildfires, pests and disease. This work presents the responses from two surveys, a random-sample telephone survey of more than 1500 residents and a mail survey targeting owners of parcels with 10 or more acres of forest. These surveys were conducted in three counties (Wallowa, Union, and Baker) in northeast Oregon, USA. We analyze these survey data using structural equation models in order to assess how individual characteristics and understanding of forest management issues affect perceptions about forest conditions and risks associated with declining forest health on public lands. We test whether forest understanding is informed by background, beliefs, and experiences, and whether as an intervening variable it is associated with views about forest conditions on publicly managed forests. Individual background characteristics such as age, gender and county of residence have significant direct or indirect effects on our measurement of understanding. Controlling for background factors, we found that forest owners with higher self-assessed understanding, and more education about forest management, tend to hold more pessimistic views about forest conditions. Based on our results we argue that self-assessed understanding, interest in learning, and willingness to engage in extension activities together have leverage to affect perceptions about the risks posed by declining forest conditions on public lands, influence land owner actions, and affect support for public policies. These results also have broader implications for management of forested landscapes on public and private lands amidst changing demographics in rural communities across the Inland Northwest where migration may significantly alter the composition of forest owner goals, understanding, and support for various management actions.
Journal Article
Missing millions: undercounting urbanization in India
2019
The measurement and characterization of urbanization crucially depends upon defining what counts as urban. The government of India estimates that only 31% of the population is urban. We show that this is an artifact of the definition of urbanity and an underestimate of the level of urbanization in India. We use a random forest-based model to create a high-resolution (~ 100 m) population grid from district-level data available from the Indian Census for 2001 and 2011, a novel application of such methods to create temporally consistent population grids. We then apply a community-detection clustering algorithm to construct urban agglomerations for the entire country. Compared with the 2011 official statistics, we estimate 12% more of urban population, but find fewer mid-size cities. We also identify urban agglomerations that span jurisdictional boundaries across large portions of Kerala and the Gangetic Plain.
Journal Article