Day: April 29, 2010

Exploiting Geographic References of Documents in a Geographical Information Retrieval System using an Ontology-based Index

/ Matt Artz

GeoInformatica, Volume 14, Number 3 / July, 2010

Nieves R. Brisaboa, Miguel R. Luaces, Ángeles S. Places and Diego Seco

“Both Geographic Information Systems and Information Retrieval have been very active research fields in the last decades. Lately, a new research field called Geographic Information Retrieval has appeared from the intersection of these two fields. The main goal of this field is to define index structures and techniques to efficiently store and retrieve documents using both the text and the geographic references contained within the text. We present in this paper two contributions to this research field. First, we propose a new index structure that combines an inverted index and a spatial index based on an ontology of geographic space. This structure improves the query capabilities of other proposals. Then, we describe the architecture of a system for geographic information retrieval that defines a workflow for the extraction of the geographic references in documents. The architecture also uses the index structure that we propose to solve pure spatial and textual queries as well as hybrid queries that combine both a textual and a spatial component. Furthermore, query expansion can be performed on geographic references because the index structure is based in an ontology.”

Clark Labs Releases New Global Monthly Data Archive for Image Time Series Analysis

/ Matt Artz

Clark Labs is pleased to announce they have released a DVD archive of monthly global NDVI (Normalized Difference Vegetation Index) and EVI (Enhanced Vegetation Index) MODIS data. The MODIS data were processed by NASA Goddard from the Terra sensor projected on a 0.05 degree climate modeling grid. The DVD includes over 3 gigabytes of data from the MOD13C2 product, for the years 2000 – 2009, formatted and preprocessed for immediate input into the IDRISI GIS and Image Processing software. None of the original values were altered. The DVD is available for only $30 plus shipping and handling.

Historical data is crucial for the analysis of earth trends and dynamics, particularly for change detection and prediction and long-term image series analysis. Time series analysis is critical for exploring such global events as El Nino and related sea surface temperature anomalies and impacts. Although such data is a valuable resource for analysts, publicly available and typically free, a significant amount of effort must be invested before the data is ready for analysis. Files for each time period, typically at sizes of over 100 mb, must be downloaded individually. The data then needs to be imported and pre-processed. This archive allows analysts and researchers to bypass the tedious yet necessary data download and preparation process, freeing up more effort for a project’s analytical goals.

This data archive is a particularly significant resource as input for the Earth Trends Modeler application within the IDRISI software. Earth Trends Modeler, an application for the exploration and analysis of image time series data, includes a coordinated suite of data mining tools and a variety of techniques for the extraction of global trends and the impacts of climate change. The new data archive can immediately be used within Earth Trends Modeler.

The DVD also includes monthly atmospheric temperature data from Remote Sensing System (RSS), processed from the Microwave and Advanced Microwave Sounding Units on NOAA polar-orbiting platforms and in a 2.5 degree grid.

Learn more about the Global Monthly Data Archive Series.

[Source: Clark University press release]

Spatio-temporal Analysis of Forests under Different Management Regimes using Landsat and IRS Images

/ Matt Artz

Institute for Social and Economic Change, Bangalore, Working paper 213, 2009

“Following the empirical study, cloud-free satellite data were used to study the forests in multi-temporal dimensions. Use of remote sensing data with visual observation/ground truth data is an advanced tool to study and understand the development patterns of the forests. Based on the vegetation index and land cover map a sound development has been observed in the community conserved forest (CCF) in comparison to other forests of the region. Community-based conservation would contribute to new conservation approaches that facilitate achieving the goal of sustainable landscape development in the mountains of the Indian Himalayan region.”

Evapotranspiration and Water Use Efficiency in a Chesapeake Bay Wetland under Carbon Dioxide Enrichment

/ Matt Artz

Global Change Biology, Volume 16 Issue 1 , Pages 234-245 (January 2010)

IAHONG LI, JOHN E. ERICKSON, GARY PERESTA, and BERT G. DRAKE

“Wetlands evapotranspire more water than other ecosystems, including agricultural, forest and grassland ecosystems. However, the effects of elevated atmospheric carbon dioxide (CO2) concentration (Ca) on wetland evapotranspiration (ET) are largely unknown. Here, we present data on 12 years of measurements of ET, net ecosystem CO2 exchange (NEE), and ecosystem water use efficiency (EWUE, i.e. NEE/ET) at 13:00–15:00 hours in July and August for a Scirpus olneyi (C3 sedge) community and a Spartina patens (C4 grass) community exposed to ambient and elevated (ambient+340 μmol mol−1) Ca in a Chesapeake Bay wetland. Although a decrease in stomatal conductance at elevated Ca in the S. olneyi community was counteracted by an increase in leaf area index (LAI) to some extend, ET was still reduced by 19% on average over 12 years. In the S. patens community, LAI was not affected by elevated Ca and the reduction of ET was 34%, larger than in the S. olneyi community. For both communities, the relative reduction in ET by elevated Ca was directly proportional to precipitation due to a larger reduction in stomatal conductance in the control plants as precipitation decreased. NEE was stimulated about 36% at elevated Ca in the S. olneyi community but was not significantly affected by elevated Ca in S. patens community. A negative correlation between salinity and precipitation observed in the field indicated that precipitation affected ET through altered salinity and interacted with growth Ca. This proposed mechanism was supported by a greenhouse study that showed a greater Ca effect on ET in controlled low salinity conditions compared with high salinity. In spite of the differences between the two communities in their responses to elevated Ca, EWUE was increased about 83% by elevated Ca in both the S. olneyi and S. patens communities. These findings suggest that rising Ca could have significant impacts on the hydrologic cycles of coastal wetlands.”

The Potential for Gray Wolves to Return to Pennsylvania Based on GIS Habitat Modeling

/ Matt Artz / 1 Comment

Papers in Resource Analysis, Volume 11, 2009

Jared G. Beerman

“The gray wolf is an animal that is often misunderstood. Due to negative stereotypes of gray wolves, they were hunted to the brink of extinction in the contiguous United States of America. Presently, numerous states (Minnesota, Wisconsin, Michigan, Idaho, Montana, and Wyoming) are implementing reintroduction and management plans to rebuild the wolf population. Geographic Information Systems (GIS) were used to identify potential areas for wolf expansion based on habitat requirements in the state of Pennsylvania. This study used information from research compiled on existing wolf packs in the contiguous United States, along with management and reintroduction plans to locate suitable land for gray wolves located in the state of Pennsylvania. The approach was to use numerous data layers to determine if any land could support wolf existence and where these ranges would be located. Key layers used to locate wolf pack ranges in this study included: road density, human density, and land cover. The suitable locations were then examined to determine: water availability, prey density, and total range size. Once these locations had been identified, an approximation of potential pack size was then determined based on range size. The results of this study show there are multiple ranges which could potentially be used for gray wolf habitation in Pennsylvania.”

Spatial and Temporal Analysis of Drought and Summer Precipitation in Nepal under Climate Change

/ Matt Artz

IOP Conference Series: Earth and Environmental Science, Volume 6, Session 29, 2009

Madan Sigdel and M. Ikeda

“Agricultural production and water resources in Nepal are highly influenced by precipitation for an entire year. In addition to dominant rainfall during summer monsoon over Nepal (SMRN), drought indices, which were normalized with the mean rainfall, were analyzed in association with large-scale atmospheric patterns using various statistical analyses. The indices at 3-month and 12-month represent agricultural and hydrological time scales, respectively. A dominant oscillation in SMRN exists in the range of 2.5–2.8 years indicating El Nino and Southern Oscillation (ENSO): i.e., less rain over eastern and central Nepal during El Nino. The analyses of horizontal patterns of moisture transport regressed on the SMRN revealed that the SMRN variability is more closely related with the moisture flux in a near-surface layer from Bay of Bengal under influences of ENSO rather than the moisture flux from the Arabian Sea. The 12-month drought index is basically equivalent with SMRN. On the other hand, the 3-month index additionally exhibits less rain in winter over western Nepal associated with weak westerly. Therefore, higher probability of the drought risk is suggested for agricultural production in western Nepal. While Indian Ocean Dipole was also investigated, its influence on Nepal is limited. These results suggest to us to prepare more appropriate mitigation methods for high risk of drought under climate change in different ways between western Nepal and the other regions.”