Day: April 5, 2010

Algorithms for constrained k-nearest neighbor queries over moving object trajectories

/ Matt Artz

GeoInformatica, Volume 14, Number 2 / April, 2010

Yunjun Gao, Baihua Zheng, Gencai Chen, and Qing Li

“An important query for spatio-temporal databases is to find nearest trajectories of moving objects. Existing work on this topic focuses on the closest trajectories in the whole data space. In this paper, we introduce and solve constrained k-nearest neighbor (CkNN) queries and historical continuous CkNN (HCCkNN) queries on R-tree-like structures storing historical information about moving object trajectories. Given a trajectory set D, a query object (point or trajectory) q, a temporal extent T, and a constrained region CR, (i) a CkNN query over trajectories retrieves from D within T, the k (≥ 1) trajectories that lie closest to q and intersect (or are enclosed by) CR; and (ii) an HCCkNN query on trajectories retrieves the constrained k nearest neighbors (CkNNs) of q at any time instance of T. We propose a suite of algorithms for processing CkNN queries and HCCkNN queries respectively, with different properties and advantages. In particular, we thoroughly investigate two types of CkNN queries, i.e., CkNNP and CkNNT, which are defined with respect to stationary query points and moving query trajectories, respectively; and two types of HCCkNN queries, namely, HCCkNNP and HCCkNNT, which are continuous counterparts of CkNNP and CkNNT, respectively. Our methods utilize an existing data-partitioning index for trajectory data (i.e., TB-tree) to achieve low I/O and CPU cost. Extensive experiments with both real and synthetic datasets demonstrate the performance of the proposed algorithms in terms of efficiency and scalability.”

GIS for Marine Protected Areas: National Marine Protected Areas Center

/ Matt Artz / 1 Comment

“In order to manage the complex issues affecting the nation’s MPAs, managers often turn to technology for help in understanding and analyzing the resources and environments of their MPAs. MPA managers and scientists are increasingly using geographic information systems (GIS) to manage, map and analyze the resources under their jurisdiction.

“A geographic information system is a computer system capable of capturing, storing, manipulating, analyzing and displaying data that describe the geography of a particular place. Often considered a mapping tool, a GIS offers a way to view, query, interpret, and visualize various sorts of spatial data to reveal geographic relationships, patterns, and trends. Maps, charts, and analytical reports can be derived from the data stored in a GIS as a means of documenting and explaining spatial patterns and relationships to assist in planning and decision-making processes.

“The MPA Center uses GIS to manage information related to marine protected areas throughout the United States to help better understand the spatial patterns of MPAs, the resources they protect and the effectiveness of MPAs as a marine management tool.” …

Can Payments for Watershed Services Help Finance Biodiversity Conservation? A Spatial Analysis of Highland Guatemala

/ Matt Artz

Journal of Natural Resources Policy Research, Volume 2, Issue 1 January 2010 , pages 7 – 24

Stefano Pagiola, Wei Zhang, and Ale Colom

“Payments for environmental services (PES) are a promising mechanism for conservation. PES could either provide additional funding for protected areas, pay land users to conserve biodiversity outside protected areas, or both. PES require a secure long-term source of financing to work effectively. Obtaining payments directly for biodiversity conservation is difficult, however. In most cases, water users are the most likely source, either directly or indirectly. Thus the potential for PES to help conserve biodiversity depends, in a large measure, on the degree to which areas of interest for conservation of water services overlap with areas of interest for conservation of biodiversity. This paper examines the extent of such an overlap in the case of highland Guatemala. The results show that this potential varies substantially within the country, with some biodiversity conservation priority areas having very good potential for receiving payments, and others little or none. Overall, about a quarter of all biodiversity conservation priority areas have potential for receiving payments. Thus PES are far from being a silver bullet for biodiversity conservation, but they can make a meaningful contribution to this objective.”

Spatial Analysis of Three Agrichemicals in Groundwater of Isfahan using GS+

/ Matt Artz

Iranian Journal of Environmental Health Science & Engineering, 2010, Vol. 7, No. 1, pp. 71-80

M. M. Amin, A. Ebrahimi, M. Hajian, N. Iranpanah, and B. Bina

“The purpose of this study was to undertake a spatial analysis of total organic carbon, electrical conductivity and nitrate, in order to produce a pollution dispersion and prediction map for the investigated area in the province of Isfahan in Iran. The groundwater samples were collected from a zone as a pilot study area of 80 km2, including 25 water wells, based on the criteria of vulnerability assessment projects, that is, about one well per 3 km2, during four seasons in 2008-09. In order to make any inferences about the areas that did not have well data, a statistical relationship between explanatory total organic carbon, electrical conductivity and nitrate variables related to well coordination was developed. The probability of the presence of elevated levels of the three compounds in the groundwater was predicted using the best-fit variogram model. According to spatial analysis, the highest R2=0.789 achieved was related to electrical conductivity and followed the exponential model with 0.266 for NO3- (spherical model) and 0.322 for total organic carbon (exponential model) in the spring 2009. This showed the high confidence level for electrical conductivity dataset and forecasted trends. The results of the spatial analysis demonstrated that the transfer trends of electrical conductivity in the groundwater resources followed the route of groundwater movement in all seasons. However, for nitrate and total organic carbon, a definite trend was not obtained and pollution dispersion depended on many parameters.”

ITA Face a Dedicated WEBGIS for Added Value Information Delivery

/ Matt Artz

Paper accepted for presentation at the 2010 European Space Agency Living Planet Symposium, Bergen, Norway, 28 June to 2 July 2010:

Massimo, Musacchio; Buongiorno, Fabrizia; Doumaz, Fawzi

“The main goal of the geophysical cluster within SAFER project is to define, develop and demonstrate tools and products, based on the EO data, to support the risk management decision procedures. This is achieved through the generation of specific products created by using EO data and the dissemination of the information to the end-users in a form suitable for decision making.

“The SAFER project will provide support to the crisis risk management activities (Volcanoes and Earthquakes) in Europe and on Demand outside Europe. For this reason the set of products, that has been selected in the preparatory phase, cover the needs related to crisis phase of the volcanic and earthquakes risk. The facility will be provided with geophysical features selected in order to use it into specific areas, in Italy and in France for volcanoes and Italy and Romania fpr Earthquakes.

“The following main objectivies are foreseen, 1) a data handling tool supporting the reception, acceptance and preprocessing of the input data, 2) a web-GIS Analysis tool supporting the analysis and long term monitoring of the products (including an MMI with the end-user, 3)processing module supporting the generation of the products and their the storage in a local DB.”

Analysis of Shoreline-Changes Based on the Geometric Representation of the Shorelines in the GIS Database

/ Matt Artz / 1 Comment

International Journal of Geography and Geospatial Information Science, Volume 1, Issue 1, 2010

Tarig A. Ali

“In this paper, the relationship between shoreline-changes and shoreline-curvature has been studied based on the representations of shorelines in the GIS database using a new concept called shoreline-segment orientation. This method determines shoreline-curvature based on the angular deviation of each shoreline segment from its neighbors and also from the line that connects the shoreline’s nodes; introducing two types of orientations local and global. Six shorelines in the study area mapped over 28-years have been used to study the relationship. Average shoreline-changes have shown higher correlation with local shoreline curvature than with global. Results also suggest that concave shoreline-segments experience more erosion than convex and straight ones.”