Guonian Lv

Topological relationships calculation for 3D curves data set based on monotone chains

Topological relations are research focus in 3D GIS. Constructing nodes and arcs from curves, building the topological relations of these primitives with their parent geometry and other geometries, and forming the topological graph, are the basis of the calculation of topological relationship. The formal description and smallest set of topological relationships of 3D curves are given. The line segments intersection algorithm computational geometry and the traditional line segments intersection algorithm in GIS are discussed, and a new algorithm based on the monotone chains are proposed to building the topological graph. The method of curves splitting and intersection algorithm of curves are analyzed. Topological graph is constructed based on the label of the topological primitives. Then, a comparison between the monotone chains method and the tradition algorithm is listed. Some experiments are carried out to testify the algorithm performance.

Research on Universal GML Parser Based on IGSD

Functional structure and framework of a universal GML schema-based parser, along with design and implementation of the integrative grammatical and semantic database(abbreviated to IGSD) that is the core component of GML parser, have been discussed in this paper. IGSD lays the foundation for GML grammar validation and universal parsing of GML data. Whereas universal GML parser based on IGSD would provide a public platform for many GIS researches on spatial data issues, such as storage, compression, index, query, retrieval, transformation, exchange, transmission, integration and sharing, etc. Keywords-GML(Geography Markup Language); UGSP(Universal GML Schema-based Parser); IGSD(Integrative Grammatical and Semantic Database)

Spatio-Temporal Constrained Human Trajectory Generation from the PIR Motion Detector Sensor Network Data: A Geometric Algebra Approach

Passive infrared (PIR) motion detectors, which can support long-term continuous observation, are widely used for human motion analysis. Extracting all possible trajectories from the PIR sensor networks is important. Because the PIR sensor does not log location and individual information, none of the existing methods can generate all possible human motion trajectories that satisfy various spatio-temporal constraints from the sensor activation log data. In this paper, a geometric algebra (GA)-based approach is developed to generate all possible human trajectories from the PIR sensor network data. Firstly, the representation of the geographical network, sensor activation response sequences and the human motion are represented as algebraic elements using GA. The human motion status of each sensor activation are labeled using the GA-based trajectory tracking. Then, a matrix multiplication approach is developed to dynamically generate the human trajectories according to the sensor activation log and the spatio-temporal constraints. The method is tested with the MERL motion database. Experiments show that our method can flexibly extract the major statistical pattern of the human motion. Compared with direct statistical analysis and tracklet graph method, our method can effectively extract all possible trajectories of the human motion, which makes it more accurate. Our method is also likely to provides a new way to filter other passive sensor log data in sensor networks.

Remote estimation of chlorophyll-a concentration in turbid water using a spectral index: a case study in Taihu Lake, China

Abstract Chlorophyll-a concentration (Chla) is a key indicator of water quality, and accurate estimates of Chla using remote sensing data remain challenging in turbid waters. Previous research has demonstrated the feasibility of retrieving Chla in vegetation using spectral index, which may be the potential reference for Chla inversion in turbid waters. In this study, 106 hyperspectral indices, including vegetation, fluorescence, and trilateral indices, as well as combinations thereof, are calculated based on the in situ spectra data of 2004 to 2011 in Taihu Lake, China, to explore their potential use in turbid waters. The results show that the normal chlorophyll index (NCI) ( R 690 / R 550 − R 675 / R 700 ) / ( R 690 / R 550 + R 675 / R 700 ) is optimal for Chla estimation, with a determination coefficient ( R 2 ) of 0.92 and a root mean square error (RMSE) of 14.36     mg / m 3 for the data from July to August 2004, when Chla ranged from 7 to 192     mg / m 3 . Validation using the datasets of 2005, 2010, and 2011 shows that after reparameterization, the NCI model yields low RMSEs and is more robust than the three- and four-band algorithms. The results indicate that the NCI model can satisfactorily estimate Chla in multiple datasets without the need of additional band tuning.

Efficient encoding and decoding algorithm for triangular discrete global grid based on Hybrid Transformation Strategy

Abstract Grid codes are an important part of a grid system and provide a unique identifier for the cells in the spherical triangular discrete global grid, where the transformation between geographic coordinates and grid codes is the basis of global spatial data integration and various analytical applications. Owing to the particularity of the topological properties, the spherical space cannot be continuously paved with the same grid cells as those in the plane space. Thus, the recursive approximation method is typically used to establish the transformation algorithm between the geographic coordinates and the grid codes. The efficiency of those algorithms that were based on recursive approximation obviously decreased with the increased grid subdivision level; thus, it is not conducive to the integration of massive high-resolution spatial data. Whereas the geometric properties of the grid cells in the spherical triangular discrete global grid differ during the initial subdivision levels, as the level increases, these geometric properties tend to be the same, along with the properties of the local regions similar to the plane. Considering this characteristic, this paper proposes a hybrid bidirectional transformation algorithm. In the proposed algorithm, the recursive approximation method is used at the lower level where there is a large difference in the geometrical properties of the grid cells, and the direct mapping method using a similar plane grid is used at the higher level where the geometrical properties of the grid cells are virtually the same. In experiments conducted using the proposed algorithm with geographic coordinates at different scales and grid codes at different levels, the running time remained stable with no significant change throughout increases in the hierarchical level. Further, it was proven to satisfy the requirements of the absolute accuracy evaluation method. Compared with the traditional recursive approximation algorithm, the proposed algorithm has obvious advantages in the transformation between grid codes and geographic coordinates, as it can better support spatial data integration and various analytical applications in the spherical triangular discrete global grid system.

GIS-based family tree system integration

With the advancement of electronization and digitization of family tree, information sharing and function integration have become the bottleneck of the development and application of family tree. To address the problems such as the existing family tree systems are mutually closed and incompatible, family tree information representation is incomplete and non-standard, time and space information implied in family tree information is not well excavated and expressed, family tree information is repeatedly collected by each system, this paper proposes to parse and position family tree information under the Consistently Spatial-temporal Framework by using GIS technique, in order to regularize the expression and sharing of family tree information. Absorbing the VGI idea, people are encouraged to collaboratively collect and share family tree information. This paper discusses some key issues about the integration of family tree systems from aspects of the Consistently Spatial-temporal Framework, information sharing, interoperability, application mode etc. It designs a prototype of integration framework of family tree systems based on GIS and implements it by taking HXJP-GIS system and DZP-PGV system as an example. The practice indicates that the framework is feasible. It provides some new conceptions, reference methods and technical supports to construct the Chinese Family Tree Database and Platform for better protecting and utilizing family tree.

GIS-based family tree information sharing and service

To address the issues of family tree information sharing, mining and spatial-temporal analyzing, this paper introduces database, network and GIS technologies into the research of family tree. It studies the mode of family tree standardization, digitization, spatialization and networking, and discusses the theory foundation, implementing techniques, cooperation platform of family tree information sharing based on GIS. Firstly, according to the elements and characteristics of Chinese family tree by learning bibliographic and content of genealogy, this paper develops a description specification of Chinese family tree information. Then, based on consistently spatial-temporal framework, a family tree spatial-temporal data model cored with person and event is designed, and the system of family tree geographic information service is established. Finally, it proposes to construct a website group of the Family Tree GIS integrating surname website, clan website and personal blog, in order to gradually build a community-based, open, multi-level platform for family tree information sharing and serving which serves for both general public and experts.

Design and Implementation of Integration Framework for Terminal-Oriented Mobile GIS Data Collection

Based on its characteristics of quickness, portability and friendly interaction interface, mobile GIS for spatial data collection has become an important developing direction of GIS as well as a major method for GIS data collection. However, the current mobile GIS data collection studies mainly focus on the implementation of mobile calculation but overlook the integrative mechanism for mobile data collection. Based on the background information that mentioned above, this paper launched a design and implementation research on integration framework for terminal-oriented mobile GIS data collection. The integration framework mainly includes two parts: first, a version-based data distribution and retrieval mechanism; the second, a data transmission mechanism called offline transmission environment which applies to different data transmission modes between server and mobile terminal. Through Nanjing Municipal Facilities Collection System, this paper gives a detailed description about the implementation of this proposed integration framework to validate the feasibility and validity of it.

3D geological modelling based on 2D geological map

ABSTRACT Current methods for constructing a 3D geological model of an area require field drilling or measured section data which are often not available over large areas. 2D geological maps not only contain information on the distribution of geological strata but also provide sufficient geometric, topological and semantic information for 3D geological modelling. This paper presents a method for constructing a detail 3D model from 2D geological maps. First, a series of parallel cross sections is automatically created from the 2D geological map and the corresponding relationships of the geological objects in the cross sections are recorded. Second, a contour algorithm is used to connect these cross sections to establish a 3D geological model of the study area. The spacing of cross sections has strong impact on the result, we proposed a rule to determine the spacing of cross sections adaptively. As a case study, the method was applied to construct a 3D geological model for Xing-gang area in Chongqing city. The results of this case study suggest that the method is effective to construct a quality 3D geological model solely based on the information from a 2D geological map of the area.

Research of robustness evaluation method for GIS vector data digital watermarking algorithm

Digital watermark technology of GIS vector data consists of designing the digital watermark algorithm and evaluating the digital watermark algorithm performance, also, robustness is a most important evaluation indicator of the digital watermark algorithm performance, therefore, this article focuses on evaluating the robustness of digital watermark algorithm of GIS vector data.