Xiaoping Rui

A novel approach for generating routable road maps from vehicle GPS traces

Public vehicles and personal navigation assistants have become increasingly equipped with single-frequency global positioning system (GPS) receivers or loggers. These commonly used terminals offer an inexpensive way for acquiring large volumes of GPS traces, which contain information pertaining to road position and traffic rules. Using this new type of spatial data resource, we propose a novel approach for generating high-quality routable road maps. In this approach, a simplified road network graph model uses circular boundaries to separate all GPS traces into road intersections and road segments and builds road networks that maintain their identical geometric topologies through the entry/exit points at the original boundaries. One difficulty inherent to this type of approach is how to best determine the appropriate spatial coverage for road intersections. Conflict points among GPS traces that have large intersection angles usually occur within the physical areas of road intersections, particularly those involving left turns. Therefore, we determined a proper circle boundary for individual road intersections by conducting a spatial analysis of such feature points. This approach was implemented using Python and PostgreSQL/PostGIS and was tested in Huaibei City, China. Based on a comparison with human-interpreted results, the automatically generated routable road map was demonstrated to be of high quality and displayed detailed road networks with turning at various at-grade intersections, interchanges and U-turns.

An effective buffer generation method in GIS

Buffer Analysis is one of the most important functions of spatial analysis in GIS. This paper uses rotation transform point formula and recursion method to further improve on the vector buffer generation algorithm of double parallel lines and circular arcs, simplifies the process of the generation of parallel lines and the circular correction of sharp angles, and finds a better solution to intersection problem of borderlines of buffer zone.

An OGC standard-oriented architecture for distributed coal mine map services

Abstract GIS- or CAD-based technology has been widely used for cartographic maps in coal mines, but structural gaps between such maps make it difficult to provide an integrated map service, for any specific purpose, at higher levels. There is no uniform platform that can be used to manage all involved maps. The main reason for this is that datasets are submitted by individual coal mines using their individual, diverse software. No consistent model is used within the software for data abstraction and symbolization. This paper first reviews all the essential specifications concerning OGC (Open Geospatial Consortium) interoperability. Then an OGC standard-oriented architecture is proposed to provide distributed coal mine map services. Within this new architecture the management of spatial data archives, and the integration of coal mine maps, are achieved through the interfaces of geospatial services. Finally an open source geospatial approach is suggested to implement the proposed scheme. A case study of the Huaibei Coal Group is used to demonstrate the proposal.

Polycyclic Aromatic Hydrocarbons in the Dagang Oilfield (China): Distribution, Sources, and Risk Assessment

The levels of 16 polycyclic aromatic hydrocarbons (PAHs) were investigated in 27 upper layer (0–25 cm) soil samples collected from the Dagang Oilfield (China) in April 2013 to estimate their distribution, possible sources, and potential risks posed. The total concentrations of PAHs (∑PAHs) varied between 103.6 µg·kg−1 and 5872 µg·kg−1, with a mean concentration of 919.8 µg·kg−1; increased concentrations were noted along a gradient from arable desert soil (mean 343.5 µg·kg−1), to oil well areas (mean of 627.3 µg·kg−1), to urban and residential zones (mean of 1856 µg·kg−1). Diagnostic ratios showed diverse source of PAHs, including petroleum, liquid fossil fuels, and biomass combustion sources. Combustion sources were most significant for PAHs in arable desert soils and residential zones, while petroleum sources were a significant source of PAHs in oilfield areas. Based ontheir carcinogenity, PAHs were classified as carcinogenic (B) or not classified/non-carcinogenic (NB). The total concentrations of carcinogenic PAHs (∑BPAHs) varied from 13.3 µg·kg−1 to 4397 µg·kg−1 across all samples, with a mean concentration of 594.4 µg·kg−1. The results suggest that oilfield soil is subject to a certain level of ecological environment risk.

A web-mapping system for real-time visualization of the global terrain

In this paper, we mainly present a web-based 3D global terrain visualization application that provides more powerful transmission and visualization of global multiresolution data sets across networks. A client/server architecture is put forward. The paper also reports various relevant research work, such as efficient data compression methods to reduce the physical size of these data sets and accelerate network delivery, streaming transmission for progressively downloading data, and real-time multiresolution terrain surface visualization with a high visual quality by M-band wavelet transforms and a hierarchical triangulation technique. Finally, an experiment is performed using different levels of detailed data to verify that the system works appropriately.

A GIS-oriented location model for supporting indoor evacuation

With increasingly large location data sets, improvements in query efficiency and reductions in location update costs have become important issues. For indoor evacuation, due to the different characteristics of indoor and outdoor environments, it is not easy to monitor and query evacuation objects using existing methods. Therefore, in this study, a geographical information system (GIS)-oriented location model called the velocity range and marked cell (VRMC) model is established, which includes three processes: (1) the generation of indoor geometric spaces called indoor marked cells (IMCs) and two auxiliary structures, the connection matrix and the tendency cells, oriented by GIS; (2) the construction of a VRMC-tree index based on Equation (1) for efficiently supporting new emergency queries; and (3) usage of the interaction between the objects’ velocities and the IMCs as an update strategy to filter the indoor positioning results. As demonstrated by simulative and real positioning data sets, the proposed model improves the query efficiency for evacuation objects, compared with existing indoor indexes and update strategies, and makes further progress toward resolving the trade-off between emergency query precision and server-side update costs.

Spectral unmixing using linear unmixing under spatial autocorrelation constraints

This paper presents a spectral unmixing approach that is implemented using linear unminxing method by a genetic algorithm. The unmixing is constrained not only by the negativity and sum-to-one of the abundances of endmembers at each pixel but also by the spatial autocorrelation of their abundances among eight neighbor pixels. The Morans I indices are proposed to describe the spatial autocorrelation among a pixel and its neighborhood. Based on the above constraints, the objective of unmixing by genetic algorithm is to minimize the mean square error of mixed spectral values. We tested this approach using Chinese HJ-satellite images and obtained an acceptable result.

Effective techniques for interactive rendering of global terrain surfaces

Global terrain visual systems must support real-time visualization and manipulation of huge multiresolution geographical datasets. In this letter, we focus on certain key techniques, such as construction of three-dimensional (3-D) ellipsoidal models, spatial indexing mechanisms, interactive terrain datasets simplification by the M-band wavelets and triangulation techniques, and surface browsing from different view directions. Finally, an experiment is carried out using different levels of detail data; our results suggest that the methods are effective in enhancing performance of a 3-D global visual system.

A weighted clustering algorithm for clarifying vehicle GPS traces

This paper presents a weighted clustering algorithm based on the physical attraction model, which improves the physical attraction model by assigning a different weight to the position points on a GPS trace for a fast convergence according to their velocity and directional changes. The physical attraction model pulls together traces that belong on the same road in response to simulated potential energy wells created around each trace. Assuming a vehicle with a high velocity has a little derivation to the road it runs on, we assign a high weight to its trace in the physical attraction model so that the clustering progress converges rapidly and closely to road. Within the clustering process, an angle-threshold based smoothing filter is appended to keep the consistency between the changes of those points on the adjusted trace at each loop. This algorithm was demonstrated to enable to effectively clarify those vehicle GPS traces on the same road. In comparison of previous work, it also shows an improved quality grouping GPS traces near road-crossing area by embedding the smoothing filter in clustering process.

Forest fire spread simulation algorithm based on cellular automata

Traditional models result in low efficiency and poor accuracy when simulating the spread of large-scale forest fires. We constructed an improved model that couples cellular automata with an existing forest fire model to ensure better time accuracy of forest fire spread. Our model considers the impact of time steps on simulation accuracy to provide an optimal time step value. The model was tested using a case study of forest fire spread at Daxing’an Mountain in May 2006. The results show that the optimal time step for the forest fire spread geographic cellular automata simulation algorithm is 1/8 of the time taken for cellular material to be completely combusted. When compared with real fire data from Landsat Thematic Mapper (TM) images, our model was found to have high temporal and spatial consistency, with a mean Kappa coefficient of 0.6352 and mean accuracy of 87.89%. This algorithm can be used to simulate and predict forest fire spread and is also reversible (i.e., it can identify fire source points).